If anyone could help, I would greatly appreciate it.

My 1992 500E cannot hold a charge beyond about a day or two. Also, since this started becoming a problem, I've also experienced some very strange sunroof behavior (the sunroof opened by itself, it will not respond to the switch, but you can help the motor working/clicking from the rear of the car, then the sunroof might work fine).

There's a control module in the passenger side engine compartment - in a bolted black box just in front of the passenger side windshield. There are three such units in there - they look like tiny little servers. One has 3 10amp fuses in it.

My mechanic has traced the problem to this control module (don't know if I'm describing it properly) that is intermittently drawing 2 amps and draining the battery. If I take the fuse closest to the passenger out, the draw goes away. If we leave it in, the car will eventually have a dead battery.

Any help? My mechanic has ordered a new module to swap out with this one (about $500 from the dealer - apparently a hard-to-find unit).

Thanks in advance.

Frank
Tampa

Sounds like you're on the right track. A 2AMP draw is enough to drain the battery in a day or two.

These magic boxes are typically impossible to troubleshoot, but since it is a short, you might get lucky with the module on the bench and an ohmmeter connected, disconnecting the obvious components that might be causing the short. These components would be such things as diodes and other possible voltage regulator components.

Anyone familiar with electronic components could do this and you might get lucky. Without schematics it's somewhere between difficult and impossible to go any further.

Good luck,

Any thoughts on whether these units regularly fail? The car is 12 years old with 155k, so some failures are no doubt to be expected.