rfl882

Hello all,
Recently picked up a 2003 C240. Only 55k miles. Runs and looks great except for electrical issues. New battery and alternator but no head lights, turn signals, brake lights, radio. All fuses and relays have been checked and are good. Little things are odd also. Rear window wiper will turn on by itself and run. Front running lights (bottom of front bumper) stay on all the time so I need to disconnect battery. Only paid a few thousand for car due to known issues, so if I can work this out on my own I will have a fantastic car for a great total cost. Any advice would be greatly appreciated.

(car was owned by an older friend of the family who had health issues and passed. Car sat for approx 2 years

MercBzC240

If car sat somewhere for a long period of time, rats could have eaten wires and you may have shorts?

They may have tried to fix stuff causing more issues?

Does it have any fault codes on the display?

rfl882

I was concerned about that too but there was no evidence of rats or mice. In my other searches I came across some similar issues that were caused by attaching a new battery incorrectly. I think that's why the alternator was fried. I have an error concerning the alternator that has not cleared even after installing the new one.

MercBzC240

If the battery was crossed by the previous people then from what I've learned about my elec issue is that the MERC have a very sensitive electrical system.
There are three units called SAMs. They are wireless controllers that talk to the ECU. They each control different functions. If you look at which fuse position you're having problems they may point to one of the sams. The rear sam is commonly fried by water getting in the trunk as it literally sits right by the hinge. Any mold of gunk blocking your trunk IE yours was sitting for two years. Can damage the SAM in turn not letting certain functions work. So find out where your issues are coming from rear or two front SAMs and it'll help you get somewhere. I don't believe the rear sam controls headlight functions though.
Your SAM may be functioning but hte signal may not be getting through. My guess for this vehicle you're gonna have to literally try and go through all hte wiring or figure out a way to get access to MERC benz STAR program to see whats going on because I feel those are your only options.
Replacing things you "guess" are the problem can get costly.

As for the battery being crossed, it would more than likely fry something that would require attention as for me turn signals are important
my GF has a BEnz so i'm in the painful learning stage. Im pretty damn good with older fords though haha

rfl882

OK. Thanks. Yeah, I have a Silverado that I have very little problems working on.

I may have to suck it up and bring her to a shop and diagnose it..

Thanks. Any other suggestions would be greatly appreciated.

bcapjoe

Check your radio. There are 3 plugs on the left side of the radio in the back. Bottom is power, middles is to all the speakers. Don't know exactly the top does but its part of the alarm system and the telephone system. Unplug the top plug and see if everything doesn't start working.

bcapjoe

Pull out the radio. In the back on the left there are 3 plugs. Bottom plug is for power. Middle is speakers. Top is part of the alarm, telephone and I don't know what all it does. Unplug that top plug and check to see if everything is working right except the steering wheel radio controls. Had some similar problems and the radio is the problem. Radio does still work with top plug unplugged

bcapjoe

Pull out the radio. In the back on the left there are 3 plugs. Bottom plug is for power. Middle is speakers. Top is part of the alarm, telephone and I don't know what all it does. Unplug that top plug and check to see if everything is working right except the steering wheel radio controls. Had some similar problems and the radio is the problem. Radio does still work with top plug unplugged