Seattle Citroën
SM Wiring on USA Models
UPDATED
10/2024
As noted in other sections of this article, the wiring was different on North American models. Some of the differences include side marker lights, headlights, the door buzzer system, the seat belt warning system, hazard lights, electric antenna wiring, over rev buzzer, and leak finder wiring.
SCHEMATICS
A set of schematics have been found that show USA model wiring. These schematics should be applicable to 1973 Canadian SM's as well. However 1971 and 1972 SM's in Canada are a bit of a hybrid between USA and Euro wiring.
I created a 'key' for these wiring harnesses. If readers spot any errors, please let me know and I will correct it.
Key for Schematics (click to open)
USA Harness Schematic (they are easier to read if you save them to your computer)
USA Functional Schematic (they are easier to read if you save them to your computer)
Note that these schematics do not include wiring associated with the seat belt warning systems and for the Borg Warner automatic transmission. (See the next sections.)
OTHER WIRING RESOURCES FOR NORTH AMERICAN SM's
I found a few more wiring resources for North American cars, including an extract from a service bulletin that has some information on wiring associated with the Borg Warner automatic and for air conditioning HERE.
SEAT BELT WARNING SYSTEM WIRING
I finally found a schematic for the seat belt warning system for the SM. It is very similar to that of the DS and uses most of the same parts, but the SM has a relay in the system that the DS does not. If you look at the seat belt warning system schematic, I think that the relay might have been drawn wrong internally, but the rest of the schematic looks correct. You can see the SM seat belt warning system schematic HERE. You can see a video demo of the seat belt buzzer HERE.
ENGINE OVER REV WARNING SYSTEM
Partway through the SM's production run, Citroën designed a system for the SM that would sound a buzzer if the engine RPM exceeded 6400 RPM. The system used the fuel pump shutoff safety module (located behind the glove box) and an input from the tachometer. The buzzer itself was mounted under the ashtray.
According to the parts books, this system was installed on all automatic (Borg Warner) SM's globally after March of 1973. But this seems to be erroneous, for several reasons.
Citroën released Tech Bulletin #29 in April of 1973 indicating that all US and Canadian cars (automatic and 5-speed) would receive the over rev warning system. If the Tech Bulletin is accurate (and I am reasonably sure it is), this is a unique installation, only for North American cars built after March of 1973.
Since this system is not shown on the USA schematics (above) or in the Parts Book, the only reference to the additional components and unique wiring harness is in the Tech Bulletin.
Tech Bulletin #29 S
Engine Over-Rev Warning System (click to open)
Jacek Wierzbivki
Over Rev Buzzer on Bottom of Ashtray (missing the cover?)
ANNOYING DOOR BUZZER
A buzzer was incorporated on all USA/Canadian SM’s to indicate if a door was open when a key was in the ignition switch. This system was added to comply with Federal Motor Vehicle Safety Standard (FMVSS) #114. More information about the door buzzer system can be found HERE.
The buzzer module was located behind the left side of the dashboard. The interior light wiring and the buzzer are shown in zone 102-105 on the USA Functional schematic above.
It is worth noting that if the buzzer is disconnected in the wrong way, the interior lights stop working.
AXO Door Buzzer used on North American SM's and DS's
COMPONENT LOCATION BEHIND DASH
Since some of the components unique to North American cars are not identified on the schematics or in other manuals, I have attempted to help identify some of their locations behind the dash....
George Klein
George Klein
Behind the Dash on North American SM's
(click to enlarge)