'93 500E Battery Drain, Fuse #9, Symptoms Listed - PeachParts Mercedes-Benz Forum

ashyers · #1 06-17-2009, 12:09 AM

The 500E has developed a problem recently and I'm having a tough time sorting it out. I have a battery drain that's taking place through the following lamps with the key removed:
E20 Exterior Lamp Switch Illumination
E10/2 Left Air Outlet Illumination
E12 Trans Selector Illumination
E10/3 Right Air Outlet Illumination
? Rear Head Rest Illumination
? Rear Sunshade Illumination
? Left Seat Memory Illumination

In addition the Radio functions w/o the key in the ignition.

If Fuse #9 is removed the draw on the battery stops.

I'm hoping that someone has had this problem in the past and can point me in the right direction. I have tried disconnecting the CD player, Power Antenna, Audio Amplifier, and Door/Hood/Trunk Switches, but this has had no effect on the draw. Any ideas here? I'm gradually pulling the car apart chasing this thing and can't say that I enjoy pasting wiring diagrams together from 8 1/2 x 11 print outs! Thanks in advance for any help

!

Andy

Mr Project · #2 06-17-2009, 08:05 AM

Any chance the ignition switch just isn't turning 'off' electrically?

ashyers · #3 06-17-2009, 09:34 AM

The ignition appears to be turning off completely. All components not listed turn off as they should when the key is switched off, including any dash related lights not on Fuse 9.

amg280 · #4 06-17-2009, 09:36 AM

Try browsing through this thread. Alot of good places to start:

http://www.peachparts.com/shopforum/showthread.php?t=253866&highlight=400e+battery+drain

ashyers · #5 06-17-2009, 12:41 PM

Thanks,
I'd read that thread a few days back and checked most of the items listed. I did measure the draw across fuse 9, it's .39-.40A. I'm diving into the dash to check some items today.

UPDATE: Just found the "Control Unit, Instrument Switch Lighting". It's some type of fancy relay with P/N 003 545 63 32. This has been replaced by P/N 004 545 08 32 according to the dealer. Anyone know how to test one of these things? It's connected to the problem interior lamps and I suspect it may be toast.

Andy

david s poole · #6 06-17-2009, 02:32 PM

all the stuff you have listed is running from a feed at the light switch for parking lights.the relay you found could certainly be the culprit.try disconnecting the wire to terminal 30 on the relay and see if draw goes away.

ashyers · #7 06-17-2009, 03:26 PM

Removed the Control Unit completely and powered up the car. The instrument lights go out, BUT the radio still functions! I've unplugged both amps and this had no effect. I'm going to try uplugging the head unit and see what happens. If that does nothing I'll take a run at the headlamp switch, once I figure out how to remove it!

UPDATE: Removed or Unplugged entire Radio Assembly (head unit, amps, cd, tuner). No change, still have draw. Called Becker NA for some advice. Told the Radio Assembly is set up to stay on for 1hr. after ign. is turned off (?!). Either way, I still have the draw of the instrument lamps. I'm inclined to get the Becker looked at for other reasons, but the insturment lamps are driving me nuts! Control Unit is looking more suspicious...

Andy

ashyers · #8 08-19-2009, 11:04 AM

Problem was the headlamp switch. Thanks for the suggestions and help!

Andy