'88 190e 2.3. new bosch battery, 900cca. suddenly engine idle rpm drops, radio cuts in/out, use ofANY electrical functions-- brake light, window, lights, etc.--seems to cause an electrical drainincreasing symptoms until car stalls, then its stone dead. needs battery recharge, runs again without symptoms for a few weeks--then problem reappears. mechanic says alternator, starter check out ok. what the hell? voltage regulator? whereis it anyway? thanks for any help.

 

One of your battery cables may be shorting to ground. If I had the problem I would be looking for wires with a bad place in the insulation. When the battery is charged, do all the accessories work ie window motors, switches etc. A short circuited accessory motor can drain the system down too.
If you have an amp meter, you can snap the loop around one of the battery cables, while the car is off, and see if there is short. There should only be less than .2 amps to run the clock and the computer. Blue

 

everything works fine when battery is fully charged except for r rear window-never worked. thanks for the help. wonderingif a bad ignition switch could cause this problem; it has just started jamming when i try to start car.