Electrical problem repeated! WHY???

[m7m]

Shortly after having a simple mechanical job done by MB dealer, the following stopped working:
In-car front and back lights (the ones that turn on when the door is opened), front left passenger window, central locking only works with infrared (not radio) signal.
Battrey discharged due to not using the car for a while. After charging the battery, everything started to work.
Explanation: removing the power from the onboard computer erased the temporary memory.
Few day later, the problems re-appeared, except for the back in-car light(the one over the back seat) still turns on when any of the doors is opened.
Conclusion: Something is writing to the temporary memory to make the parts stop working.
Why?????

 

[Diesel Benz]

Wrong conclusion. You don't mention the car model but some consumers are automatically switched off on new cars when the battery voltage drops but you would get an indication at the cluster and everything would be back once the battery gains charge.

What sort of simple mechanical work was done with the car?

 

[m7m]

ooooppss! forgot to mention:
1. The car is 11 years old E200.
2. Mechanical problem = fan belt. Hence, unrelated to the electrical problems that occurred afterwards.
3. The battery was discharged a couple of weeks after the occurrance of the faults

 

[cyberflex]

Guys, do these cars have signal acquisition modules? (SAM's).
If so, sounds like symptoms of failure, from stuff I have read on here..

 

[m7m]

Guys, do these cars have signal acquisition modules? (SAM's).
If so, sounds like symptoms of failure, from stuff I have read on here..

Can anyone tell me what is the "signal acquisition module"?

 

[andy27168]

Hi,
Though I believe you have a SAM it is a basic unit unlike the later MB's item, yours is a lot less prone to failure.
If you are happy the car battery is in good condition, I would get a STAR test done as it sounds like you have a part of the CAN system losing communication.
Though I,m by no means an expert, but I think it will be either a door control module, or the overhead console unit that is duff.
Incidently have you got a sunroof? does this stop working or operates erratically when the fault occurs? If so I would personally think it was the overhaed console unit.
The STAR test should indicate which item has lost communication, though this fault log maybe erased if the battery is disconnected/reconnected, and you then would have too get the test done once the fault reoccurs.

 

[cyberflex]

Thanks Andy for chiming in to help this guy. No one has really come in, I guess, due to the way the poor guys first post was worded.. I felt guilty for not helping more, but did not want to offer misleading advice. Your diagnosis makes logical sense. Cheers.
m7m, just for info mate:http://www.evilution.co.uk/539
All the best.

 

[kwakdonut]

ooooppss! forgot to mention:
1. The car is 11 years old E200.
2. Mechanical problem = fan belt. Hence, unrelated to the electrical problems that occurred afterwards.
3. The battery was discharged a couple of weeks after the occurrance of the faults

This may sound daft but does the 'fan' belt not also drive the alternator? This would then be related as an alternator not charging correctly will cause problems with the battery?

 

[m7m]

1. Last week, I had the battery checked. It is in good condition and charging corretly. Hence, the above faults may not be related to battery. (It was discharged because I did not use the car for a long time).
2. car has no sunroof

 

[kwakdonut]

OK, just trying to delete various possible issues!

 

[m7m]

The main aim at the moment is to explain why do the electrical faults disappear after the battery is removed and reconnected, and why do most of them return?

I can live with the present faults, but worried whatever is causing the faults will cause something else to go wrong.

 

[cyberflex]

I think the ONLY way to get to the bottom of you worries is to either go back to the dealer who did the work and explain the situation, your car needs to be connected to STAR to check proper function of the various electronic modules your car has, they may give you a discounted rate as they have been involved before, they may not....
If not, please search the forum for independant specialists in and around your area, that all have STAR Diagnosis, there are some excellent specialists on here, if you are willing to travel a bit, this is the only way to find the offending module or wiring without blindly wasting time/money on components that may not be at fault.