[R129 SL] Electrical problems when it rains

[Mike Preiss]

For the benefit of anyone who ever gets this problem, a solution has been
found. Moisture was getting into the X4/10 terminal block and causing a
short on a corroded connector. Since this is where power from the battery
gets to the engine compartment and instrument cluster, this caused the
electrical chain reaction of symptoms I saw. An interesting point is that
water was not clearly visible in the block. Water had to get heated up in
the engine compartment to create vapor, which would then create just enough
contact to cause an intermittent short. The corrosion on the connector was
almost invisible, just a little less shiny than the other connectors.
 
If you ever see strange engine and electrical behavior by your car when it
gets wet, this would be a good place to start looking. In my case, it took a
lot of persistence with my dealer (who like most dealers just wanted me to
buy lots of expensive parts) to get this resolved. 
 
Mike Preiss
91 500SL


  _____  

From: r129list-bounces at mbcoupes.com [mailto:r129list-bounces at mbcoupes.com]
On Behalf Of Mike Preiss
Sent: Monday, May 16, 2005 10:14 AM
To: r129list at mbcoupes.com
Subject: [R129 SL] Electrical problems when it rains


I'm hoping someone can help with this. My dealer is baffled after a working
on my car for a week. Every time I get my car washed, even if it's a hand
wash, or when it rains, my 91 500SL acts up. The instrument cluster lights
up like a Christmas tree, the gas gauge goes dead but speedo still works. On
starting from a stop the car stalls and stumbles badly, and at idle when in
Drive will often stall. Will run in Neutral though. After a day or two, of
dry weather, the problem goes away. Of course the dealer just wants to
replace the ECL and instrument cluster ($5000 just for parts) but admits
that might not fix the problem. I don't agree that the computer or the
cluster are fried, since the problem disappears after time to dry. Also, how
would water be getting to both just by coincidence?
 
Logic would seem to indicate water is getting to something in common to the
engine computer and the cluster. My guess is a cable connecter somewhere is
letting water in and causing a short, but where? Any help greatly
appreciated.
 
Mike Preiss
91 500SL
 


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