Citroen XM Forum

Gentlemen,

Somewhat hypothetical scenario; late S2 V6 24V auto, into early S1 (1990) shell.

Thoughts?

Ciarán

You will need TCT set engine mount points I think... A complete harness swap from dash, down nearside chassis leg and across the engine..

To be honest Ciaran, do it the other way, which someone HAS done on here, put S1 dash into the S2 car... Possibly a far easier way!

As mentioned by Paul there has been a conversion of a S24v by James who is on the Forum occasionally. I saw the car and James briefly at the Chervons Rally and understood the task was not too epic! Regards, Matthew T.

The degree of difficulty depends a bit on which transmission was originally fitted to the shell was auto or manual, and also whether the engine is from an XM, Xantia or other.

I would probably not change the wiring harnesses other than the engine/transmission harness, or you could end up chasing your tail with S1/S2 changes.

I believe that the 4HP20/XM driveshafts are unique to that model.

If you did proceed, I have quite a few of the parts available from the ES9 auto car that I dismantled.

If you change engine transmission harness you WILL NEED to fit the corresponding harness in the car because citroen changed the Plug Format/Setup behind the glove box..

I know this from experiance. When I stripped a poor H reg SED I thought I KNow, Ill fit the SED harness (1990 Car) into a 1994 L reg Base model and make that an SED auto, to gain rear leccie windows Power for leccie seats, etc etc... BUT, OH NO, the Dash harness plugs behind the glove box would not match up to the L reg Chassis leg harness... so, I had to swap that over, and then the Engine and trasmission harness would NOT match up to that, so I had to put that in too in the end.... SO, its not where near as simple to just switch two harness's, they will ALL need swapping from the donar!!

Whichever way the wiring is done, it is not plug and play, individual wires will need splicing. I think that it is easiest to do it all in the harnesses under the bonnet (especially if the shell already has a gear indicator display).

Another point to consider is that the only hydraulic pump that will easily fit the es9 is a 6+2.

If it a petrol car and uses the same box i would splice it in between the engine and car loom plug under the LHM tank, well its what im going to do, i will buy a new waterproof plug and pin it as i see fit. The ecu will need power, the starter will need a trigger as will the fuel pump, guages and warning lights will want signal and thats it running, obviously it s bit more involved than that to get the creature comforts going but thats just time.
Everything under the bonnet that keeps the engine running just needs power to the right places at the right time, it is pretty much stand alone with the older engines, the newer engine will likely need FBW throttle? and the newer HP20 box will require a lot of work i would guess, the selector and wiring for mode selection and warning lights on the dash and of course fitting an ecu never intended to be in the car will require some electricity, i would think the gearbox ecu talks to the engine ecu via the engine bay loom only.

D

Do you have a little project on the cars Ciaran?

D

The throttle on the first gen esj engine is nechanical flap and cable and not motorised...

Pinning is a lot of work certainly when most wires are all the same colour just with faded id numbers along the lengths of them. Loom swaps would still be my bet and quickest if you had access to the complete donar car

citroenxm wrote:The throttle on the first gen esj engine is nechanical flap and cable and not motorised...

Pinning is a lot of work certainly when most wires are all the same colour just with faded id numbers along the lengths of them. Loom swaps would still be my bet and quickest if you had access to the complete donar car

But every harness in the entire car is different between a 1990 car and an ES9 car, even assuming that the donor is an XM.

Body shell differences for XM's are minor.
Somewhere I have a 1995 note listing how to modify a Mk2 shell to rebody a Mk1.
It listed things like "drill bulkhead hole for speedo cable.

The wiring for a retrofit gives a series of choices as listed above.
I do not think there is a right answer as to which to use.
It depends on resources to hand and the skills available.
Researching tech docs including loom and wiring diagrams is not for everybody.
A practical "when I see it I work out what to do" solves items one by one for quite a few people.
However it is done we gain on here if progress is written up by our very valued contributors.

John