battery drain


Old 12-19-03, 03:30 PM
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battery drain

I have a 1989 GMC Suburban which has a new battery. Lately, when it sits for several days, the battery is totally dead.
I've had the battery and alternator checked out and they are OK.
I disconnected the negative terminal and put a test light between the terminal and the cable. The light is bright. I removed fuses until the light went out. The fauly circuit powers the radio, cabin lights and horn relay according to the owner's manual.
I removed the radio and the light is significantly less bright, however, it still lights dimly. I have checked the vehicle in total darkness and no lights are on. The underhood lamp is switched and is not on. The horn works normally.
What am I missing here?
Any suggestions?
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Old 12-19-03, 04:31 PM
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Join Date: Oct 2003
Location: Boynton Beach Florida
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When you perform this test you need to put a jumper wire across the test light for a minute or two to expire all the timers first. You could have a horn relay sticking or the radio could be the problem. That fuse only powers "keep alive memory" and the clock. The cabin lights also use a module for a timer.
Old 12-19-03, 04:34 PM
Join Date: Dec 2002
Location: Connetisuck
Posts: 162
To do this test accurately you need to install an ammeter instead of that test light. 32 Milliamps is approx max draw. Make sure the door is shut, and the vanity morrors, etc are closed and key is out of the ign.
Old 12-19-03, 04:38 PM
Join Date: Nov 2002
Location: San Francisco Peninsula
Posts: 121
Since we are on this subject: If you hook up a Milliammeter instead of a test light, what milliamps are allowable for steady drain, e.g. at what reading should you worry about excessive drain?
Old 12-19-03, 04:45 PM
Join Date: Jun 2002
Location: Long Island, NY
Posts: 1,531
To check for a draw on modern computerized systems you need a Digital amp meter capable of reading ma's.

Test lites use to work when the only device to draw was a electro-windup clock. Today a good system will draw 50 ma or less. You will find some high end Lincoln, Caddy etc that will draw 90 ma and still be ok.

You also need to have the circuit "live" with an ampmeter in the circuit. By using a test lite it is not. There are timers and caps that need to cycle or charge up before you can measure the draw.

See if you can measure the draw and post back the numbers.

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