1987 190D - Battery Drain Issues
 

A friend's 190D was serviced and driven home. Every other morning, the vehicle lost charge and had to be jumped started or charged manually. Are there any common charging/drain problems to look for first?

I would say firts remove and have the battery tested,then if not battery test the alternator,2 very good places to start and common problems.
Good luck to you.
It also helps to make sure you have the right battery and alternator installed,a lot of times with these cars you find modifications and other butcher type creative ideas installed in them,like i just bought a car that had the alternator bracket installed wrong and wrong alternator belt size kept drainning my battery,but i believe the 190 d has a single serpentine belt so it doesnt apply but just as an example.

Vehicle has been owned by the same owner since 1988...no mods. I also asked him about possible incompatible components.

Battery and alternator have been tested (both good). I was thinking it might be something electronic (i.e. the power seat module draining the battery on my former 1997 E420).

I in no way know if your model has it or if the symptoms are the same, but I have read about the voltage regulator acting a fool. I also hear the the power antenna can be a drain.

Thanks...have you read about the glowplug relay also being a source of drain??

The glow plug relay is not your issue.

To find the drain proceed as follows:

Disconnect the negative battery cable and put an ammeter in series between the cable end and the battery negative post.

The reading should be about 50-60 ma. But, it will be higher than this level.

Then, start pulling fuses until you find the one fuse where the reading drops down below 50-60 ma. That's the culprit circuit. Now comes the more difficult part of finding which device on that circuit is leaking current to ground.

The confirmation of a leak above 100mA is the first step in the process.

Pay close attention to what was done when the car was serviced. If they did some electrical work, you might want to start looking there.

Look at the second post at this link; the owner had extensive service done to this car at a dealership: http://www.benzworld.org/forums/w201-190e-d-class/1360947-restoring-8-000-mile-2-3-a-56.html