1990 MERCEDES BENZ SL300 BATTERY DISCHARGE

  • Tiny
  • Humvee
  • 1990 Mercedes Benz SL300

Electrical problem
1990 Mercedes Benz SL300 6 cyl Two Wheel Drive Automatic 93000 miles

I have a 1990 SL300 that the battery goes dead after a day. The car is usually stored in a heated area but now its in an unheated garage. This problem just seemed to start when we had our fisrt real freezeing temps.
I hooked a Snap-On graphic meter between the battery. Bypassed the trunk light and the meter read a 0.110 amp draw. I have done the following tasks without finding the problem or reducing the draw. Removed fuses and fuseable links in 3 fuse boxes one at a time. Disconnected the alternator. Removed the aftermarket radio. Car is completly original and well maintained. The exception is that an aftermarket radio was installed a couple of years ago.
Could there be a stuck relay?
Is there a fuse or fuseable link not located in the 3 boxes?
Backfeed from one circuuit to another?
Is there a timer icircuit that is not shuting down?
Any ideas would be helpful.
Thanks

Sunday, December 13th, 2009 AT 9:57 AM

4 Answers

  • Tiny
  • buddycraigg
  • Expert
  • 2,322 posts

Wow, you have tried everything that I would have suggested that a normal person with a limited tool box to do.

The next thing to do is start tracing every circuit after you print out the schematics.

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Monday, December 14th, 2009 AT 2:59 AM
  • Tiny
  • Humvee
  • Member

I guess it's time to start pulling the dash. Thanks

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Monday, December 14th, 2009 AT 8:09 AM
  • Tiny
  • buddycraigg
  • Expert
  • 2,322 posts

I tried looking at the schematics for any hidden fuses or links, but my on-line program has chopped the manual up so bad that I couldn't follow the pages.

Do you have a manual with a good wiring diagram in it?

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Tuesday, December 15th, 2009 AT 12:08 AM
  • Tiny
  • Humvee
  • Member

Mine are also in about 20 sections/groups. At least they are not in German.

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Wednesday, December 16th, 2009 AT 4:24 PM

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