I know this subject has been kicked over many times but in reading past posts, I'm somewhat confused. The 85 I just purchased has a fairly new battery and seems to take a charge very well. If I leave the car overnight, the battery will be so dead the next morning it won't even lite the interior lights. I read in a past post were someone pulled a fuse and used a trouble light on the connector where the fuse was? Does anybody understand this way of troubleshooting? Or is there another that will isolate the curcuit?
I was going to try this weekend and find this problem so any help would be great...

save the wave!
david

 

Somewhere you have leakage current that discharges the battery overnight and it could even be within the battery. First charge the battery up with a battery charger, then connect an ammeter in series with one of the battery posts and its cable. Start the ammeter out on its highest scale and wait for the courtesy lights to time out. Then switch the ammeter to lower full scales until you can read the leakage current. Normal leakage current should be under 50 milliamps. My 87 draws 27 ma. If you have high leakage current (it takes about 3 amps to discharge a battery overnight), start pulling fuses from your fuse block and watch the ammeter. One fuse pulled that dramatically drops the leakage current will be the circuit that you will have to investigate further. By the battery there is a bolt with 8 wires that have fusible links. You will need to take the nut off and disconnect these wires one at a time to determine if leakage current occurs in one of those 8 circuits. If you still haven't found the high leakage current, you will have to go to the several circuit breakers and either disconnect them one at a time , or get a clamp on dc ammeter and measure the current through them to find what circuit is drawing current. If you find no circuits drawing current , but the battery till discharges overnight, I would suspect a battery at the end of its life.

 

Thanks for your procedure. My main question is/was the way I read an old post, a person would pull a fuse, then connect the clamp side to one side of the fuse connector, and touch the test light to the other. Still not sure thats what they meant but plan to try tomorrow. After watching the weather here in texas I might have to wait till fall!

thanks again,
david

 

I am sure that the post you are talking about uses a low power 12v lamp that you connect across a pulled fuse. If that circuit has significant leakage current , then the lamp will light.
Some things you can check at night is if a vanity mirror has been left on or if an underhood light is stuck on, or if the light in the console map compartment is stuck on.