C270 CDi Electrics

[C270 CDI]

Hi all, I'm new on this site but thought I'd give it a go as the other forum I've been using has come up with no answers on this one!

I'm asking for some help before I take the final step and send my Front SAM off for a re-programme.
I've posted before and listed the electrical problems I have with the car (2001 51 plate C270 cdi), but have not been able to resolve them.
To summarise, I've got the following going on:

Engine fan runs constantly (regardless of engine temp or running time).
No auto headlights (although they work fine off the switch).
No auto wipers (as above, but on position 1 they just wipe intermittently).
No interior lighting.
No heating or ventilation (the panel is dead with no illumination when lights on, and I have just changed the panel this week with no change).

I have had these problems since February when I got the car back after crashing it. A couple of weeks ago all the problems disappeared and I had everything working and no engine fan running, but when I hit the AUTO button on the heater control panel everything immediately stopped working and the engine fan came back on.
This led me to think that the heater control panel could be at fault, but like I said having changed it I still have the problems.
Now I'm thinking I could possibly have a problem with one (or more) of the relays and want to test them before I remove the SAM and send it off. But if there is a problem with the SAM why did everything start working again (and it's not the first time this has happened)?
Can anyone tell me which relays are which, and how to test them please?

Sorry it's a bit of a long-winded post but there's a lot of things going on here, and I don't want to throw any more cash at it than I have to.

Oh and by the way I had it diagnosed at a MB indie and his Star system came up with nothing definite, and I wasn't happy that he just wanted to take the car to pieces just to try and find the problem.

 

[allias]

You said you changed panel - are you sure it was correct part number? Was accident you had? Maybe some part of harness id damaged and thats the reason.

 

[C270 CDI]

Hi Allias, thanks for replying.
I think it was the correct part number. I can't help thinking that even if it was a slightly different part at least I would get illumination on it when I turn my headlights on?
The accident was a low speed (10-15 mph) spin-out on the ice. The bonnet, bumper, headlight and wing (all driver's side) were replaced. The door was repaired too. I've been on to my insurance company about this and they haven't been too helpful.

 

[allias]

Do you have details for your car as well as part number for panel? I can check that for you.

 

[C270 CDI]

Sorry but all my documents are at home in Plymouth and I'm at work in Portsmouth.
All I can tell you is that it's a 2001 (51 plate) C270 CDi Elegance saloon.

 

[allias]

Sorry but all my documents are at home in Plymouth and I'm at work in Portsmouth.
All I can tell you is that it's a 2001 (51 plate) C270 CDi Elegance saloon.

Can you PM me your reg and part number of unit you installed? There is number of different units that could go inside your car. So far I caunter about 4 models but I think with different models it can get to 8-10. So if you used one (used of ebay) there is a chance you have wrong one.

 

[C270 CDI]

Yeah I'll do that when I finish work later.
Thanks for your help on this.

As a point of interest, would you agree though that even though it was a part off e-bay and it's possibly a different control unit to the one already on the car, it should at least have illumination when the lights are turned on?

 

[allias]

Yeah I'll do that when I finish work later.
Thanks for your help on this.

As a point of interest, would you agree though that even though it was a part off e-bay and it's possibly a different control unit to the one already on the car, it should at least have illumination when the lights are turned on?

It could be same shape but different internals/wire connections and that might cause problems.

 

[C270 CDI]

I tried to PM you but as I don't yet have a 30 post count the site won't let me do it.
The reg is WV51JJO and the part number (i think) of the replacement control unit I fitted is: A203 830 07 85.
Thanks.

 

[allias]

One thing for sure - if that the part number then that is correct one for your car.

- if its SAM unit you looking for £209+vat if its new.

 

[BlackC55]

I would get it on a Star diag machine first before bolting parts on. It is probably the SAM that is faulty but it is best to get it checked.

I would put a new unit on rather than a second hand one.

 

[C270 CDI]

Hi BlackC55, i was going to give you a shout on the "other" forum.
I agree, it does need further diagnostic, and I will always buy a s/h part if poss (looks like i may have got it wrong this time though!).
My main concern is that the system has been (and does intermittently) work so i can't see that there's anything seriously wrong with it and that's why the previous diagnostic i had done didn't pick up anything specific - maybe there's a connection issue? I've been reading a bit here and there about "CAN" connections, would that have anything to do with it?

 

[C270 CDI]

Hi all, thought i'd post a quick update:
I hit a bump in the road on Saturday and instantly my engine fan stopped running, my heaters came on and I got my auto headlights and interior lighting back.
Weird I know, but if nothing else it proves to me that there is in fact nothing (massively) wrong with the Front SAM or the heater control unit. I'm thinking now that the problem is more than likely a loose connection somewhere, so if anyone has any more thoughts on this I'd appreciate your input.
For now though I'm just going to leave it - with winter setting in I prefer to have my heaters and forget about it until it warms up again (or it fails again!).
Thanks to everyone who replied, just proves that you don't need to go to dealers to get constructive answers and advice.

 

[Ian B Walker]

Its possible that when the accident damage was repaired an earth lead was not connected securely to good clean metal. Just a thought.

 

[C270 CDI]

Thanks Ian, that gives me something else to look at. Like I said I'll wait now until it goes again but I've got a few things to look at - and I'm more than relieved that both the Front SAM and heater control panel seem fine.