500E Electrical Diagnostic Help
 

I have a 92 500E and am trying to figure out why it has a constant 1.5 Amp draw on the line to the module box with everything off. In trying to trouble shoot this problem I have found that when the upper engine harness is pluged in the module box draws the current. The harness is new. When the box is drawing 1.5 Amps, the harness seems to be drawing 0.5 Amp (all measurements were with a clamp on DC ammeter).

As an aside, Fuse circuit 9 is drawing 350 mA with everything off - measured with a test meter in series. Most I see (from electrical schematic) in that circuit is a few relays and a run to the Diagnostic Socket/Terminal Block. Also, the radio is not installed, however, alot of the factory radio stuff is still installed, though the head unit has been replaced ba an aftermarket.

Thanks,
Lee

Anyone?
 

??

Start with ammeter connected in-line with battery, inductive readings can be misleading.

IF the rear radio unit is still connected disconnect it!

You are looking for 30-40ma.

I placed an ammeter inline to get the draw on fuse 9. Did not try it for the direct line to the module box, though. I was initially not sure if I wanted to try the ammeter inline at the battery, due to the high current mode (10 Amp) not being fused.

The current draw to the module box while the engine is running is around 5 Amps while 1.5 amps with everything off.

Thanks,
Lee