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1985 Sedan DeVille
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1,883 Posts
Discussion Starter #1
The guy that works on my old cars has a mystery problem with a '99 SLS that I told him I'd try to help diagnose, and am looking for some help getting this figured out.

When the key is put into the ON position but the car is not started, the cluster gauges (including the fuel gauge) sweep to their normal positions, the radio lights up, and all is normal.

When the car is started and key is dropped to the ON position for running, the gauges all sweep and go to running position, but the fuel gauge drops to zero and stays there, and the radio does not come on.

Here is the really weird part--if he disconnects and reconnects the battery, everything works NORMAL for a little while and then eventually goes back to the exhibited behavior. The amount of time before failure returns seems to be related to outside temperature (faster when hotter).

Looking around, it seems to me that the fuel gauge problem can be explained by a faulty sender in the ballast pump. I'm guessing that a relay is activated when the car starts that drives the ballast pump, which would explain why the gauge works when the key is ON but engine is OFF, but does not work when engine is ON. A faulty relay may also explain the situation with the battery connection. However I don't see how the radio fits into this.

Anybody got any information that would fill in the gap here? How is the ballast pump powered, by the BCM or a relay or what? How would this be affected by heat?
 

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Registered
1985 Sedan DeVille
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1,883 Posts
Discussion Starter #2
Any ideas on this?
 

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2016 Honda Accord LX. Previous: 2004 Deville, 2000 STS
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3,718 Posts
How old is the battery? When they are close to death they tend to cause all sorts of weird electrical problems that cannot be explained. The gas gauge is usually the in tank sending unit. They aren't too hard to replace, you don't have the drop the tank like you do with other cars. Also, while you're at it do a check for codes using the in-dash scanner (directions at top of Seville/Eldo forums) to see if anything comes up.

Hope that helps a little.
 

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Registered
1985 Sedan DeVille
Joined
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1,883 Posts
Discussion Starter #4
I did the ALLDATA test procedure on the sender and it's definitely bad. I suspect there is intermittent ground that is being forced by the bad sender.

Do the SLS have dual pumps for the saddlebag tank? I can only see one from the top

Thanks
 
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