Multiple Electrical Failures

[Mol]

Hi, First time posting so bear with me if I ramble a bit.

We have 2 C250 Turbodiesels, a 1998 Estate and a 1997 Saloon. Both have multiple electrical failures that I can't fathom, not helped by the poor wiring diagrams in the Haynes Manual. On the saloon I have - No central locking or blipper or auto lock when driving, no internal boot release, 3 electric windows not working (one partially down), no rear demister but the light on the dash works, the button that drops the rear headrests does not work, only one door mirror moves, and the central locking button on the dash doesnt work. This all happened suddenly, although initially all four windows wouldnt work until the drivers window started yesterday along with its mirror. I'm thinking maybe an earth tag broken somewhere.
On the estate the windows are intermittent working; central locking wont work on blipper, but will on button and when moving; rear wiper wont work - I think everything else works.
Any help would be greatly appreciated. Also I'm getting a used auto box for the estate - any things I should watch out for when changing it?
Thanks. Mol

 

[andy27168]

Hi,
Start with obvious, have you checked the fuses on the Saloon as it sounds like you may have a ignition control fuse blown.
Indeed I would check the integrity of all the fuses first on both cars first.
Throw the Haynes wiring diagrams away, they are only suitable for the earlier vehicles, though certain circuits they can be used as a guide but the circuits you are talking about they are next to useless.

 

[BlackC55]

I would be looking at a CAN fault. Needs a Star firstly to check the codes.

 

[Mol]

OK, I checked all the fuses, and all ok. There was one blown but made no difference when I changed it. Came to work Weds morning still the same, got in it to come home - everything works again. You think its possible that the battery, or even just the battery earth strap could be dodgy? Thanks. Mol

 

[meoldbangar]

When was the last time the battery was fully charged, I mean off a mains charger, not off the alternator in the car.
I had these type of problems, then I learnt that the alternator only tops up the energy lost through start. Its to do with the output of the alternator.
I put my battery on trickle charge overnight until it took close to zero current.
My problems then disappeared.
I do this every 6months now

I believe the management side switch off the non essential electrical parts of the car if there is insufficient power from the alternator and battery to run these items
Maybe after you had ran the car to work the battery was better charged and warmer, hence why the items were ok. (Just a thought) A warmer battery gives out more energy

 

[Mol]

Now that sounds very like what it has done. I dod make the comment to a couple of people who i was talking to about it that all the things you actually need to drive - engine, lights, wipers, etc... were all still working, just not the things you don't need. I managed to get into the boot when the battery was flat (no boot lock now!), charged the battery, and its been pretty much ok since then. I'm going to get new batteries and earth straps for them both eventually, just to rule all that out. Before I buy the batteries, is it normal for the saloon to have a smaller battery? Thanks. Mol

 

[guydewdney]

The estate wiper might be the relay inside the boot come off, mine did. Remove inside trim, te relay should be near the motor. Mine had fallen out.

 

[Mol]

That sounds likely, the rear wiper went first I think. I'll open it up and check. Thanks