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Evolution of the spare parts numbers

In itself, a spare part number, is just a reference of letters and numbers that do not seem to have special significance. This is also the case for some Citroën parts, but in most cases, it is possible to derive a lot of information from the numbers themselves and from the various codes that often surround the numbers in catalogues, price lists, on labels and other places. It is the intention of this article, to give an overview of the many series of spare parts number systems, used by Citroën over time, and to provide some degree of understanding of the systems and codes, Citroën has used in connection with the spare parts numbers.

Pre-war numbers

When Citroën began car production in 1919, the spare parts were assigned numbers beginning with 1 and more or less continuing sequentially. From the large, complete spare parts catalogue from 1919-28, you get the impression that the various models are just different versions of the same essential thing: The Citroën Automobile! It seems that numbers have been assigned in smaller series of the same family of parts (a series of wings, a series of front arms etc), but with no regard to what particular model a part belongs. These series, in turn, appear to have been assigned in no particular order. At the end of each of these series, there are usually unused numbers, that could be used to assign numbers to new parts of the particular type.

The only main rule is that the lower the number, the older the part is, relative to parts of the same family.

Already in the 1920'es, the numbers exceed 100.000, and when we reach the war, a lot of the numbers below 100.000 had gone out of use since they belonged to discontinued models, and those which were still in use, were therfore to to a large extent parts of a generic character, like nut, bolts, bushes, washers, bearings etc.

Parts that were initially considered to be generic standard parts were given a suffix -S. These numbers have probably been assigned along with the others, rendering them unique, even without the -S suffix. There are, however, a few exceptions to this: 2503-S is a standard M7 nut with 12mm width across flats, whereas 2503 is a washer 12.5x24.

This number series continued after the war for generic standard parts and for the models that continued after the war, hence Traction Avant and the various lorries (T23 etc). As most of us experience this number series, now after the war, it looks by and large as in the following table:

0000-S
Simple, generic standard parts, like bolts, nuts, washers, greasers etc. The number can be from 1 to 4 digits. I imagine these parts always had to be ordered in packages containing a number of pieces. Variants of a given part could be introduced into the catalogues by adding another dash and 2 digits (usually 30) to the number. For instance, a round-headed screw 5x25 has the number 2509-S, whereas the version with a rounded countersunk head is named 2509-S-30.
00.000
Generic parts that could be ordered one at a time. It is typically bearings, sealing bushes, special bolts etc. Actually, this series is not just 5 digits, but covers the interval 232 to 118.300.
000.000
The "normal" spare parts. There are, however, some series in between that have more character of being standard parts, like for instance 611.000 to 625.000.

Generally, it seems to be the rule, that parts, belonging to the same area of the vehicle, for instance the rear axle, have numbers close together in sequence. Generic parts that are similar, also have numbers close to each other, but this is independent of where they belong on the vehicles.

My best source to this system is the numerical order catalogue 424. It is from 1967 and therefore, this version is published near the end of the lifetime of this system. Maybe it was not like this from the beginning, but from this catalogue, you get the impression that there has not been a great deal of rigour or stringency in the assignment of numbers. For instance, in the interval 329.041 to 331.365, there is exclusively parts belonging to the cooling system, but right in the middle of this with the number 330.230, there is a single ampere meter. There are many examples like this.

The series do not always begin and end on whole thousands, but often on a "random" number. However, there seems to be the outline of some overall intervals, as can be seen from the table to the right.

Parts for right/left side had often separate, consecutive numbers. Whereas there is a tendency in later series that left side has been assigned the lowest number, it is often opposite in the pre-war number series. A front door for a Traction Avant has, for instance the number 224.042 for the right side respectively 224.043 for the left.

In some instances, right/left side variants could have the same number, but were separated by adding D or G at the end of the number. An example of this is one of the types of the front torsion bars on a Traction Avant, which has the numbers 427.011D resp. 427.011G.

Seldomly, a spare part number appears with an added slash and a number of two digits. This is used to differentiate variants of the same part, for instance adjustmen tshims in various thicknesses or it is used when a part is updated to a new version.

Even though a new numbering system appeared with the new post-war models 2CV, type H and all the good models that followed thereafter, these numbers continued to be used for many years (mostly for generic standard parts) until they were finally replaced by longer numbers in the age of electronic data processing, which for started for Citroën around 1969/70.

Number seriesType of parts (roughly)
1-S – 956-SBolts
999-S – 3328-S Bolts, washers, studs, nuts, sealing bushes, splits etc in small series among each other
4101-S – 4118-SBalls
4151-S – 4157-S Wedges
4730-S – 4739-S Greasers
4861-S – 5052-S O-rings
5400-S – 5500-S Nuts
232 – 724 Joints packets and other motor accessories
829 – 6278 Drain plugs, washers and other minor parts
10.378 – 88.140 Wedges, bearings and a few other things
88.148 – 88.963 Nuts, washers, lock plates and a few other items
89.015 – 118.300 Springs, bolts, bearings, washers, suspension parts
121.222 – 299.873 Accessories – body parts (glazing, doors, bonnets) and interior parts
300.832 – 317.738 Motor suspension, exhaust, battery
317.757 – 319.369 Chassis with suspension, shock absorbers, crossmembers, battery trays
319.404 – 321.394 Exhaust and a few other things
325.228Bonnet lock
329.041 – 331.365Cooling system
350.433 – 361.039 Suspension and shock absorbers
380.118 – 384.253Drive shafts, shaft brake
390.141 – 392.631Accessories for wheeels
400.016 – 409.507Differential
411.012 – 418.249Brakes
420.386 – 420.956Wheel hubs
421.008 – 421.324Torsion bar suspension
421.450 – 431.791 Rear axle and a mixture of the 4 categories above
435.077 – 445.076 Front axle with parts for brakes and steering
450.044 – 479.148 Motor and its exterior elements
480.378 – 481.730 Carburettor parts
490.063 – 493.174Clutch
500.124 – 518.024Gearbox
540.258 – 543.462Pedals
550.281 – 554.390Break pipes and main cylinder
585.162 – 596.057 Fuel tank and piping
600.374 – 604.333Steering
611.001 – 611.021Locking plates
612.001 – 612.702Mostly sealing bushes
613.007 – 613.172Rubber washers and -items
613.652 – 613.677Stainless bolts
614.000 – 614.150Hose clamps
614.201 – 614.563Electrical connectors and other small items
615.001 – 615.919Nuts
616.001 – 616.505Stag bolts
617.004 – 617.058Hinge tubes
617.256 – 617.811 Joints and mounting brackets
618.514 – 618.759Rivets
619.004 – 619.634Washers
619.643 – 619.850Clips
620.000 – 620.809Bearings
621.002 – 622.950Bolts
624.001 – 624.029Washers
648.136 – 650.260Tools
651.193 – 651.277Cabin heating
700.175 – 702.384Organs exterior to the motor
703.343 – 707.255Light and signaling
709.066 – 709.900Ignition system
710.005 – 723.532Cables, connectors and other electrical equipment
730.007 – 784.556Cylinder heads and related parts
800.713 – 811.178Body parts
910.505 – 910.509 Copper tubes in the piece

Numbers with model designation

Of all the spare part numbering systems Citroën has used over time, this scheme, from the most "golden age" of Citroën history (in my humble opinion), is the one where the spare parts numbers in themselves hold the most information.

When Citroën was to re-start after the war, they also re-designed the spare part numbering system completely. Spare parts for the new post-war models 2CV, type H etc. adhered to this system with four elements: A model code of 1 to 3 letters, an "organ" group code of 3 digits (in rare cases also 1, 2 and 4 digits) designating where on the vehicle, the part belongs, a 1 to 3 digit "serial number" for each of the particular parts in the group and finally an optional letter for possible variants of the spare part (side, colour, material etc.). When this letter designates a side, it is generally the rule that left comes before right in alphabetic sequence. Example: Left and right plastic indicator trumpet on a D-model have the numbers DM 575 6 resp. DM 575 6 A, and the corresponding parts in inox finish are named DS 575 15 B resp. DS 575 15 C.

It is not, however, always that lateral versions are differentiated by a letter. In some instances, the parts simply have different numbers and if the numbers are consecutive, it is the main rule, that the left part holds the lowest number. The glass over the headlights on a D-model (Cibié 1967-75) is for instance named DX 541 24 for the left side and DX 541 25 for the right side.

It can be quite important to be accurate with these numbers: AM 453 3 A is a bracket, whereas AM 453 03 A is a main brake cylinder. I have not seen confusions of this kind in material from Citroën (but now and then among the audience), and the only source of confusion in this respect seems to be a lack of standard practice for the alphabetization of 0 respectively lack of 0. Hence, always look a bit up and down a page before concluding that a particular part is not there.

In the guide to the usage of the numbering system (for instance two whole pages in the 2CV catalogue from 1952, no. 446), Citroën writes that it is very important to remember to quote all letters and not just the number, as one otherwise might receive a completely different part than intended. It is very true and seems to us like a no-brainer, but we have to view this in the context that until then, the spare parts references had almost exclusively consisted of numbers.

 
Citroën also makes the destinction, that the initial letters (the model code) is written in capital letters, whereas the optional suffix letter (denoting variants) is written in lower case. It is, however, difficult to see that this should ever be a source of confusion, and consequently, this practice was also dropped by Citroën themselves, who already from around 1970 wrote everything with capital letters.

Furthermore, Citroën writes that it is important to quote the dash between the organ group number and the serial number part. Otherwise, they state, one might end up receiving a totally different part than intended. In theory, this is correct, beacuse there were a few larger, assembled items (complete motor, gearbox, front axle, a whole body), which had spare parts numbers where the organ group part of could be of 1 or 2 digits. However, if you look at the numbers actually assigned, it is hardly a real problem, and this practice was therefore gradually abandoned.

Once a part has got its number, it can easily be deployed elsewhere. A few examples: The light switch in a 2CV has the number HY 522 01B, and it is therefore a fair guess that this part first saw the light of day in an HY, before also being used in 2CV. The rubber handle AZ 644 79 on the ventilation knob on a 2CV has a number corresponding nicely with model and its function in group 6, but when the same knob is re-used in group 5 for the headlight height adjustment, it still retains the name AZ 644 79.

In the spare parts catalogues containing mainly this type of spare parts numbers (plus, of course, generic standard parts), there is no separate index in the french catalogues, since the parts are already more or less in numerical order according to their organ group. Already in the middle of the 60's other number series appear and an index is added to the catalogues - to begin with, however, without the generic standard parts, which are not included in the index before the late 70's.

In all the english catalogues, the dilligent people in the office in Slough used the extra resources necessary to equip the catalogues with a numerical index of all parts.

The model codes used in the spare parts numbers are not exactly the same as the vehicle group codes, which were later used in the spare parts number prefixes after 1970. Therefore, they deserve their own table, placed here to the right.

The format of this type of spare part references in the period 1948-68 can consequently be summarized like this:

From 1969 to 1979, this was simplified by abolishing the dash and purely using capital letters:

Just around 1970-71 there was a short intermezzo where some numbers got converted to the more IT-compatible format with the extra digit "9", which is explained later in this article:

Efter this short period, the previous format was resumed (only capital letters and without dash). This then continued until around 1980 (possibly starting in 1979), where a prefix with a two-letter vehicle group code was added also to these numbers. Hence, they had this format in price lists, catalogues etc:

Model codes in spare parts numbers
AClassical 2CV until 1960
AK3CV van
ALM35
AMAmi
AMBAmi6 break
AMFAmi6 Club
AMNAmi with LHM
AMUAmi8 break
AT2CV 4x4 63-66
AU2CV van before 1960
AW2CV Sahara 58-63
AX2CV late in the 60'es
AYDyane
AYADyane 4
AYBDyane 6
AZ2CV 425cc
AZU2CV van
DDS/ID
DADS Ambulance
DBDS Break
DCDS Commerciale
DDDS21
DFDS Familiale
DJDS after 9/68 (DS21 mécanique)
DJBDS Break after 9/68
DJFDS Familiale after 9/68
DMD after 2/58
DSDS Pallas
DTDS after 9/68 (DSuper)
DVD (DSpécial)
DVFD Familiale (DSpécial Familiale)
DWDS after 8/61
DXDS after 9/66 (DS21 hydraulique)
DXND
DYD
GXGS, but special number format
HH load capacity 1200kg
HGH Diesel
HPH plateau 1200kg
HVH
HYHY load capacity 1500kg
HYNH
HYPHY plateau load capacity 1500kg
HYVH
HZH load capacity 850kg
NBelphégor, type N
NDNBelphégor, type N
PBelphégor, type P
PDBelphégor, type P
PTNBelphégor, type P
PYBelphégor, type P
SSM
SNSM
TType 55

The organ under-group numbers consist of three digits, the first of which is the spare parts group number 1-9 according to the old classification 1948-70. The next two digits are used to denote what more specific part of the vehicle the part belongs to. These numbers are also used in repair manuals and as picture references in the spare parts catalogues far into this century. They can be seen in the table to the right.

These under-group numbers are one of the most stable aspects of Citroën spare parts numbering. Even though many parts have changed main group over time, these under-group numbers remain unchanged. The exhaust system, for instance, belongs to main group 6 today, but picture numbers etc are still 182. In the catalogues of the more recent models (from around 1990) the picture numbers have four digits, but the fire three of these are still using this system.

The first under-group number, that begin with 0 may appear as an anomaly, but there is actually also an explanation for that: In the first catalogues using this system (for instance the 2CV catalogue 446 from 1952), it is explained that the under-group number does not always have to be 3 digits if whole organs are concerned. A complete motor, for instance could be named A 1-03 and on the next level a complete gearbox could be A 33-0. As time went by, the under-group numbers of one and two digits were converted by adding zeroes in front. Later, for instance, a complete motor could have the number AM 001-021 A.

Under-group number Organ groups
(1948-70)(1972-1995)
001Motor, complete and repair kit11
008Body complete87
033Gearbox complete31
041Front axle complete4
042Rear axle complete4
111Cylinders11
112Cylinder head11
113Crankshaft bearings11
114Cylinder block11
121Crankshaft, rods, pistons11
122Timing chain/belt11
123Camshaft11
124Valves11
131Timing chain cover1
132Parts mounted on the cylinder block1
133Motor suspension16
141Inlet manifold12
142Accelerator pedal and carburettor12 (+1)
143Injection system, diesel1 1 (+2 for carburettor after 1992)
144Injection system, petrol11
171Air filter12
172Turbo charger and intercooler2
173Fuel pump16
174Fuel pipes16
175Fuel tank16
181Exhaust manifold12
182Exhaust piping16
183Silencers16
184Emission control12
211Ignition system22
222Oil pump11
223Oil sump1
225Oil cooler21
231Water pump21
235Water piping26
241Cooling fan21
242Air inlet26
311Clutch housing3
312Clutch32
313Clutch disc32
314Pedals and -connections34
331Gear box housing31
332Gear box lid and sppedometer drive31
333Gear wheels and -axles31
334Gear change forks and -rods31
343Differential31
344Crown and pinion, reduction gear31
371Differential axles, main drive shaft34
372Drive shafts and outer joint34
373Inner joint34
391Hydraulic pump and -regulator33
392Break accumulator and safety valve33
393Hydraulics reservoir33
394Hydraulic pipes and related components33 or 4
411Front axle4
412Fron arms43
413Pivots43
416Front hubs and wheels43
421Rear axle4
422Rear arms43
426Rear hubs43
434Suspension43
435Anti-roll bars and height correctors43
436Shock absorbers43
437Height regulation43
441Steering wheel43
442Steering rack and -housing43
443Steering rods43
444Servo steering43
451Main brakes44
452Cooling ducts for front brakes44
453Brake cylinders and piping44
454Parking and emergency brake44
455Hand brake linkage44
456Brake regulator44
511Electrical cabling55
512Electrical equipment55
521Dashboard (instruments)55
522Dashboard (switches and accessories)55
531Battery and -frame55
532Alternator52
533Starter52
541Headlights55
544Rear lights55
545Interior lighting55
551Rear mirror55 or 8
554Sunscreens55 or 8
561Wipers55
564Washer and defroster55 or 6
571Horn55
611Steering wheel lock63
614Relays, fuses and sensors65
615Bumpers66
616Safety belts68
621Tooling (for motor)68
622Wheel accessories and -tools68
623Other tooling6
641Air conditioning system66
642Cabin heating66
643Cabin air intake66
644Climate control66
651Glove compartment and ash trays65
653Radio65
661Luggage rack67
711Chassis (classical, on lorries etc)7
721Frame76
741Front bodyparts77
742Rear bodyparts77
743Central bodyparts77
744Floors plates77
746Room divider plates77
747Lateral plates77
748Storage compartment floor77
812Front body parts87
821Panels, lateral87
825Roof87
841Front doors87
842Rear doors87
844Rear/boot door87
846Goods door and loading ramp87
847Goods door and loading ramp87
850Bonnet87
851Front wing87
852Bonnet87
853Front panel87
854Embellisher profiles and -panels87
856Dashboard87
861Door locks and -handles87
922Rear seat98
924Bench seats, front98
932Front seats88
934Bench seats, rear98
935Folding seats98
941Arm rest, front98
942Head support98
961Glazing, window winder and lateral mirrors97
962Lateral windows97
971Hood98
980Floor cover98
981Floor mats and -silencing98
982Interior trim98
983Door trim98
988Silencing in cabin98

The GX numbers

Viewed at a glance, the spare part numbers for GS have the same general form as the classical references: Model+under-group+sequence-number+letter, but they are completely different from all other number series.

The under-group numbers in the GX series are only 2 digits and the classification is fundamentally different the traditional under-group numbers of 3 digits, which were used both before and after the very short period in history where the GX-numbers were assigned. They can be seen in the table to the right.

These, completely different under-group numbers are not the only thing setting the GX-numbers apart. The format is GX + 2-digit under-group number + 3-digit serial number + 2 digite which are often 01, but can be different + plus a letter which is normally A, but can be different.

There seems to be the system that the 3-digit serial number denotes different part, whereas the 2-digit number denotes variants of the same part (colour, side etc, beginning with 01). The letter (initially always A) can be updated to B, C etc, if a part is updated over time. Here is a (rare) example of this usage of the letter, which otherwise is normally A or B:

Left/right is normally distinguished by the left side having a lower serial number (may both be the 3-digit or the 2-digit part) - never by changing letter A/B. Examples: Left/right indicator GX 60 166 01 A / GX 60 167 01 A where the difference is marked by changing the 3-digit part; Left/right sunscreen without mirror is GX 53 192 01 A / GX 53 912 02 A.

(Under-)groups in GX numbers
01Motor
03Air intake, carburettor, fuel system
04Exhaust system
06Ignition and starter
07Motor susprension
08Clutch
09Gearbox and differential
10Drive shafts
13Suspension and hydraulic system
20Front axle
21Rear axle
22Wheels
24Steering
25Brakes
31Body
40Steering wheel
41Dash board
42Pedals, handbrake handle and central console
43Climate control etc
50Cabin heating
51Radio
52Wheel accessories
53Wiper, rear lights, sun screens, safety belts
54Electrical equipment
60Head lights, front, bonnet etc
63Front wings
65Front doors
66Rear doors
67Boot door
68Cabin air intake, bonnet lock
70Front bumper
71Rear bumper
80Windows
81Front seats
82Rear seats

It looks as though the GX number series have been used almost exclusively when the GS was designed, but very short thereafter (already from some time in 1971), no new numbers have been assigned using the GX series. When GS (and later GSA) should have new parts, the other number series were used - first the 5 000 000 series and later using the other series as they came into use.

At this point in time, when Citroën had created a whole new way of dividing the spare parts into organ groups for GS, you would normally think that this would then be applied to all aspects of documentation and schemes around this new car. This is not the case, however. Even in the very first repair manual, for instance, alle operations and chapters are divided according to the classical 3-digit under-groups. The GX number series and the 2-digits organ under-groups were just a parenthesis in history.

The U numbers

This is also a number series, having its completely own format. It looks as though Citroën from around 1960 has been somewhat reluctant to allocate new numbers in the pre-war series 0-900.000. For most of the models, this was not at all a problem, since they had their own number series where the numbers began with the model code. The vans and lorries, however, had never gotten their own such series - except for type 55, whose new spare parts began with T, but even this series had not been taken whole-heartedly into use.

New spare parts for these vehicles (called les Utilitaires in French) got numbers that (naturally) started with U. At a first glance, you might think that this conforms to the system used for the ther spare parts numbers starting with a model code, but why this is not the case for the U numbers, is a complete mystery to me.

Although these numbers are usually written U 00 000, it is apparently the system that the first digit is group number according to the old system (1=motor, ... , 9=interior trim) and the next 4 digits are a serial number, which seems to be allocated sequentially from 0001, irrespective of what organ in the group or what model the part might belong to. It makes also no difference whether the part is produced by Citroën themselves, or by one of the many sub-suppliers.

A few examples: The first height corrector with LHM was named U 40 851 and its membrane U 40 848. When you encounter this in a D-model catalogue, you may find it odd that it has a "U" number. Well - this is very much in line with the Citroën tradition of testing new inventions with a smaller audience first, as these parts actually first appeared, not in the D-model, but the year before in a Type 60 bus with hydropneumatic suspension. U 50 338 is a brush holder for the plus side of a Ducellier dynamo, U 50 339 is the corresponding part the for minus side, U 40 732 is a steering column bearing for Belphégor (but re-use from T23). U 80 305 is a door lock cylinder for T23. U 90 038 is a front seat for an FOM, probably hard and uncomfortable in steel tubes and plywood.

"import" number series

Over the years, Citroën has had to distribute parts that were not produced by Citroën themselves. Many of these has just gotten a standard Citroën spare part number, whereas others have been incorporated in the programme via special number series.
DK 00 000 Used by Citroën Denmarkfor articles that the mother company did not know about. These numbers are observed from some time in the 80'es to the present. There seems to be a kind of system where the first digit is some kind of of group number, and the rest is a serial number. It is, however, certainly not any of Citroën's standard number schemes they have used. It must be completely home-brew made by the people at the Danish daughter-company in Bådehavnsgade in Copenhagen.
ZA 00..0 000 L Mainly numbers, originating from Fiat 242, used for C35. There are a few additions to that, such as a set of shims for the GS Birotor gear box. The number part of these spare part numbers can have 6, 7 or 8 digits.
ZB 9000 000 A Parts whose numbers are originally assigned by Berliet, but incorporated into the Citroën catalogues. For instance: The hydraulics pump in a C350K has the Berliet number 149 869, which is then translated to ZB 9149 869. There are sometimes a letter appended to the number (usually A), but the meaning of this is not clear to me.
ZF 00000 000 The ZF series is apparently used exclusively for the Fiat product sold as Citroën C25, where Fiat-assigned numbers are admitted into the Citroën catalogues this way.
70 00 000 000
Used for import of numbers from some time in the last half of the 70'es. When you consider what models these numbers are used for (LN, Visa, C25 and for motor parts in CX and BX), it is an obvious thought that this is numbers for imported PSA-parts from befor the time when Citroën rolled over completely from around 1994 and just started to use the 6-digit Peugeot numbers as is. It has, however, been difficult for me to find proper evidence for that theory, as I have not yet had acces to contemporary Prugeot catalogues. If anyone could comment on this, it would be very much appreciated.

Numbers have been observed to start with 73,74, 75, 77, 78 and 79, but by far, the most numbers start with 78 and 79.

Y 000 000 000 In the years around 1990, quite a number of parts for C25 got numbers in this series, which probably also was an import series.
90 00 000 000 Yet another series for import of spare parts numbers, used from the last half of the 80'es and continuing to around the same time (around 1994) when the 6-digit Peugeot numbers started to show up in the Citroë:n catalogues. Number have been observed starting with 91, 94 and 97. Whether this series replaced or simply supplemented the 78/79 series above, is not clear to me.

Generic parts

Generic standard part are those parts that (even from the outset) do not belong to any specific model, but may fit in many places. It is items such as bolts, nuts, washers, greasers, fuses and similar things that normally are sold in boxes containing a number of pieces. Generic parts can, however, also be bearings, sealing bushes, special bolts etc that are typically sold one piece at a time.

0000-S Simple, generic standard parts such as bolts, nuts, washers, greasers etc. The number can be 3 or 4 digits. I imagine that these articles always had to be ordered in packages containing a number of pieces. This series is used right from the beginning in 1919, but is converted by the end of the 1960'es the new series, especially ZC and 20 000 000.
0000-S-30 Parts like above, but in som kind of variation, like for instance a bolt with a pointed end in stead of a flat. Most frequently, -30 is added, but numbers with 10, 20, 40 and a few others are also observed.
00.000 Generic part that could be ordered one at a time. It is typically bearings, sealing bushes, special bolts etc. These numbers are converted at the end of the 1960'es to the new number series, especially the ZC series.
000.000 Some generic parts retained their pre-war numbers all the way until the end of the 1960'es, where these numbers were converted to the new series - typically the ZC series.
ZC 9000 000 U Replaces from around 1970 the numbers of the type 00.000 and 000.000. This series is both used for generic parts sold one at a time and for a range of various parts that clearly belong to a specific model, but had a past as a 6-digit pre-war number. For instance: 602.009 was converted to ZC 9 602 009 U.
ZD 9000 000 U
Generic parts such as bolts, nuts, clips etc, which were generally not model specific and had to be ordered in packages containing a quantity. Replaces around 1970 numbers of the type 0000-S.
Examples: 485-S-30 became ZD 9 029 530 U and 2319-S became ZD 9 231 900 U.
20 000 000
Generic parts. Already after a few years with the ZC and ZD series, many of them (but not all) were converted into numbers in this series. For instance is ZC 9619 899 U converted to 26 198 999 and ZD 9 482 900U to 24 829 009. New numbers are allocated in this series until around 1980.
Many generic parts have had their numbers converted from one series to another over time. This is often done retaining the central digits. An example: A sealing bush at the end of the camshaft of a D-model, had before 1970 the number 612.629. This was converted into ZC 9612 629 U and a few years later again into 26 126 299 L. A lot of generic parts have undergone both these conversions, and while it is unusual that a part retains the central digits in both conversions, it is quite common in at least one of them.

If you are searching for a particular part in catalogues or price lists, it may often be a good idea to see if the part can be found as a converted number in one of the other series, with the same digits. However, this is far from a safe method, as the subsequent conversions in many cases have been used to assign a completely new number to a particular part - also when the part itself has not changed at all.

The extra digit "9"

Another peculiarity from the turbulent years around 1970, where so many things changed, seen from a spare parts numbering perspective, is the extra digit "9" that some spare parts suddenly got in their numbers. It is most clearly seen in the index of the GS catalogue 590 from September 1970.

Here, you see that more or less all numbers of the kind with model codes have been converted to a format with an extra digit "9" inserted between the model code and the under-group number, the serial number is padded with zeros and a letter L has been added where there were no suffix letter before. For instance are the exhaust pipe clamps on the heat exchanger of a 602ccm engine is converted from AY 182-6 to AY 9182-006 L, even though it is precisely the same part. Why is that?

It is a fair guess that this conversion transformed all spare parts number into the same format at this point in time: Prefix + 7 digits + one letter, where the prefix could be either the model code (A, AM, AMN, AY, D, H, GX etc) or ZC/ZD or organ group + vehicle group letter. The letter in the end was the suffix letter that the number had in the first place and if none existed, an L was added. If the number was the in the ZC/ZD series, it already had U in this place, and if it was a number in the 5 000 000 series, the check letter was used.

As you can see from the example to the right (from the same catalogue), this had the beautiful consequence that all known spare parts number could fit in the same format, which was probably a demand for processing those in computers. This was the era of punched cards, where speedy processing of longs lists, ordered by column numbers was the order of the day.

Why the use exactly the number "9" in this place - why not some other number? The probable explanation for this could be that Citroën might have believed that all future spare parts numbers would have the same format as the newest number series at that time: The GX series. In a GX series number, the first digit after "GX" can be 0-8, but never 9. Therefore, the number "9" could be reserved for numbers in other systems. Whether this is more than just that - a theory - remains to be discovered, but it would also explain why, for instance, a standard indicator 12V/21W light bulb was converted from 706-750 to exactly ZC 9706 750 U be adding an extra "9".

There are, by the way, also a very few examples of numbers with an extra "8" added. For instance, a clutch for an HY after 1968 is named HY 8312 000 B. Where this comes from, there could be many theories about, but not clear picture appears as yet. Observations/theories from you would be welcomed!

At this point in time just around 1970, there were, for the first and only time at situation where (nearly) all parts numbers adhered to the same format. But as we know, nothing lasts forever, and as far as I can see, this didn't even last a year! The influence from Fiat was beginning to show in the spare parts catalogues with the emergence of numbers in the ZA series, and a little later came the Peugeot references in the series 78/79, neither of which was in the format of the other Citroën parts numbers.

Most of the numbers in the series beginning with model codes (A, AZ, AM, D, H, etc) continued after this brief period with their original numbers, but the few numbers that got to be converted, actually retained their new numbers with the extra digit "9". This is the reason why you may find a few numbers of this type, even in relatively recent catalogues. In the 2CV catalogue MIC01117 from 1991, for instance, you can find a ring for a Ducellier starter, which has the number DV 9533 267 A.

Sequential numbers

Just before 1970, all the numbers of the sequential pre-war type 000.000 had been phased out. The last remains of these had been converted to the espacially the ZC/ZD series. At this point in time, most of the spare parts numers contained some information about model and group. However, this lasted only just a year or two, as Citroën again created a new kind of sequential numbering of spare parts. After all the hassle of creating new number systems with model code etc since 1948, converting the remaining numbers into the ZC/ZD series in 1969/70 and all the other changes, and make conversions to allow for easier automated data processing, it may seem a bit counter-productive that Citroën did not hold on to this a little longer. Instead, they created a whole new number system, based on sequential numbering, starting with the 5 000 000 series.

Probably, Citroën has come to the conclusion, that if the standard way of processing spare parts numbers were going to be computerized anyhow, it would not make any difference if they chose simple sequential numbers. If this was the reasoning behind these new sequential numbers, Citroën themselves, in my opinion, demonstrate that this was a false assumption since they needed to add the check letter, after this system had been in use for a number of months.

With the number series 5 000 000, Citroën also starts (after a few months) to add spare parts group number and vehicle group code in front of the number and the check letter after the number. At the same time, Citroën writes that part should be ordered by quoting only the spare part number itself. Consequently, this extra information has only served as an enrichment of the parts numbers, in order to minimize errors and mix-ups at Citroën themselves and their dealerships.

5 000 000 Assigned from around 1970 to 1976  
75 000 000 Assigned 1976-79  
90 000 000 These numbers are assigned 1980-94.  
0000.00
Numbers in the system, Peugeot has used for many years before they show up in the Citroën catalogues in 1994. These numbers also have a certain system to them, but we will skip this in this article.

The format for the 5 000 000 series (and the series 20 000 000 and 75 000 000) looked 1971-79 like this:

From 1980 the check letter was dropped and the two-letter vehicle group codes were introduced:

Numbers with colour codes

If the same part existed in multiple colours before 1970, these variants simply got different spare parts numbers, either using different suffix letters or numbers in close sequence. Examples: The right front seat cover for a Dyane from 1969 is named AY 912 18 A, AY 912 18 C, AY 912 18 E resp. AY 912 18 G in the colours blue, red, grey resp. green. The year after, the design has changed and the same part has the numbers AY 912 218 A, AY 912 220 A, AY 912 222 A and AY 912 224 A in the respective colours red, blue, gold and green.

In these number series, it was also possible to take the next available number or letter, when an extra colour was invented for specific part. When Citroën changed to sequential numbers (the 5 000 000 series etc) this was not possible anymore, and furthermore it grew much more common with many colour variants for the same part.

Therefore, Citroën started adding colour codes to the spare part number, separated by an asterisk. Thus, a red dashboard for a Méhari from 1975 has the number 5 459 117*201, whereas the similar green version is named 5 459 117*405.

This method, though, was not used in all cases at the beginning of the new number series, but grew to be more and more used during the first half of the 1970'es. The bonnets for Méhari was in 1971 named 5 405 366, -367, -368 and -369 in the colours red, green, ocre and orange.

On packages and labels and in some other contexts, Citroën used a slash instead of an asterisk to separate the two parts of the number. Some kind of separation was of course necessary in order to make sure that the combined number was not mistaken for a very long spare part number.

In the last half of the 1980'es, colour codes changed from three digits to two or three letters. This meant that there was no further need for separation between spare part number and colour code. A blue switch for the rear wiper on a BX is for instance named 95 634 829 FLE. In this case, there is no asterisk or slash to separate the number itself from the colour code FLE, but on the other hand, there is no doubt possible as to what is the spare part number and what is the colour code.

This practice of no separator also found its way back into the numbers with 3-digit colour codes, which sometimes appear without asterisk or slah - as one long combined number. In a few instances, this can lead to confusion and mistakes, but this is not a big problem. The real problem with these combined numbers is the how they are sorted and placed in the index of a catalogue or in a price list. Parts with colour codes can actually be quite challenging to find sometimes.

Originally, it we the intention, that parts numbers with colour codes should be sorted in indices and other lists alongside the original spare part number. An example of this (originally intended) practice can be seen in the CX catalogue MIC 01192 from 1981:
The confusion is particularly great in the Danish price lists, there coloured parts in the 5 000 000 series are sorted between numbers in the Peugeot series, far away from other parts in the 5 000 000 series.

It runs totally amuck when if want, for instance, to find all parts in the (Danish) price list around 95 567 646. They exist in three different places:
   

Colour codes in this system are observed in connection with numbers series 5 000 000, 75 000 000 and 95 000 000, but not in combination with the series 78/79 and the Peugeot series 0000.00.

The check letter

One especially nerdy subject is the check letter, which is appended to spare parts numbers in the series 5 000 000, 20 000 000 and 75 000 0000. It appears in spare parts catalogues and on the labels of the parts.

In the very first catalogues (ie. no. 596 from 01/71) containing these number series, these numbers are written without model prefix and without this check letter appended, but in the catalogues after this and onwards until these numbers are no longer assigned, they are usually written with both prefix og with the check letter.

Apparently, there has been a greater chance to introduce an error when such a number was written by hand, on typewriter og for a typesetter than for the previous number series. Furthermore, if a digit was wrong, there were no sure way of detecting this since this wrong number would probably also be a valid spare part number, due to the fact that these numbers were generally assigned sequentially. Hence the need for a check letter to enable detection of such errors.



If you have a spare part number of this kind, you find the check letter by multiplying the spare part number by 10 and divide it by 23. The remainder (0-22) that results from this division corresponds to the letters ABCDEFGHJKLMNPRSTUVWXYZ, where A corresponds to 0, B to 1 etc. You notice that the letters most easily mistaken for digits (I, O and Q) are omitted from the check letters.

Division of a number of 8 or 9 digits by 23 is not an operation which is easily performed by hand, as you need all the digits to find the remainder. Even on a classical pocket or desk calculator with 8 digits, this operation can be problematic. The purpose of this check letter must therefore have been to identify errors in spare parts numbers when entered into a computer. You can try yourself to find the check letter for a spare part number using whis website.

The actual need for this kind of control, is demonstrated by Citroën themselves in qute a few places. In the index to volume I of the D-model catalogue 648, you find 5 404 254 U. The correct check letter for 5 404 254 is found as described above by dividing 54042540 by 23. This gives a quotient of 2349675 and the remainder 5404254-2349675*23=15. When you count forwards to 15 in the sequence of check letters (remember that A is at place number 0), you reach the letter S. A correct spare part number would therefore have been 5 404 254 S, and something is wrong. The actual error in this case, is that the typesetter has exchanged two digits in the correct number 5 404 245 U, which you can also verify in the relevant page in the catalogue.

When you test the catalogues like this, you find that this fits most numbers and usually the few deviations can be traced back to printing errors of the kind above. But these errors also demonstrate that this kind of check was not carried out consistently. The system of check letters also dissappeared again, probably when Citroën stopped assigning new numbers in these series or maybe even shortly before that.

If the spare part number has an added color code, the check letter is found based on the original spare part number exclusively. All colour variants of the same part therefor has the same check letter.

When you look at the newest spare parts catalogue for 2CV, you can still find numbers of this type. The front silencer, for instance, has the number 5 490 718, but there is no check letter which has disappeared from catalogues, pricelists and all other contexts since around 1980.

When?

An approximate summary of when the numbers were assigned in the various part parts number series, have I attempted to compile in this diagram:

References for workshop articles etc

In the Citroën catalogues, a range of other number series can be found, supplementary to all those described above. It is mostly items for workshops, sales support material and similar items of a general nature.
0000-T
Special tools - typically from the manufacturer Fenwick, sold through the Citroën organization. The number was 4 digits which seem to be assigned by Citroën sequentially in small series per organ, such that for instance motor repair tools have number 1601-T to 1700-T, clutch tools 1701-T to 1729-T etc. Other tool manufacturers also used these references in their catalogues, especially Facom.
ADD 0000000 Addenda for repair manuals. Observed in the 90'es.
AMC 0000000XPromotional clothing
BRE 000 000Catalogues of workshop articles
CAR 000000 Booklets (carnets) containing technical data and brief technical information for workshops for all models. They only appeared for a few years in the 1980'es.
CAT 000000 Spare parts catalogues - exist both on paper and microfilm. If it is a price list, there is also an H appended to the number.
IMC 0000000 A Service forms to fill in by workshops
MAJ 0000 000Model specific documentation of some kind
MAN 000 000Spare parts catalogues and repair times bookletsReparationsmanualer og faktureringstider
MIC 000 000 Microfilm spare parts catalogues. The number can have 5 or 6 digits. For catalogues after around 1990 the last digit is replaced be a letter (usually A).
OUT 00 0000 T Special tools (outillage). This series replaced in the late 70'es the series 0000-T. Example: A set of tools for lifting a CX body was first sold as 6606-T and later as OUT 50 6606 T.
SRV 000 000 Consumable materials for workshops, such as clamps, fuel filters, batteries etc.
TPS 000 000Repair times
ZCE 000 000Paint, sealing etc
ZCP 000 000Paint, sealing etc
ZCT 000 000Tools etc