My batt was dead today on my 90 after the car seemed to run fine yesterday. Not even lights would be on in the car. Nothing in first place ignition and no start. Got a jump and started it up, took it down to have the batt tested. As they tested it in the car, they said something was draining the battery continually....something very small perhaps(unless its intermittent) and I can't figure out what it is. They just said it needs to be charged so I'm charging it, and I guess Ill have to disc the batt overnight when Im not driving until I sort the problem. I dont know how long this has been going on but I had this prob(the batt dying on me about a month and a half ago. I drove up somewhere, went in about 15 minutes, came out and the batt wouldnt start, had to jump it. Its either an intermittent problem Im thinking, or the drain is super small and eventually affecting it over time slowly?. They tested the alternator and it tested ok at about 13 and a half. I didnt see any lights or switches left on in the car save for the rear view mirror click light which has no bulb in it(it was switched on). I wondered if this could cause a small drain even if theres no bulb in there or light going on? Before I take it to any electrical shop that rapes my wallet for a diagnostic I'm trying to see if I can find out what it is with a voltmeter/multimeter I just bought. I don't know much about electrical, but what would be the best way to check? Can I put the voltmeter on the connected battery when the car's off and while reading the meter, start pullin fuses from the fuse compartment and see if the reading goes away?
I also had a prob with the right rear stereo speaker a while back in that I seem to remember it was drawing too much power somehow in the wiring and crapped out because of it when I went to have it diagnosed. I replaced the rear speakers and had new ones put in shortly after that but its been a while. Is it possible a rear speaker could be drawing power and leading to the problem? They said a common issue was stereo amps drawing power when the car's off, but I wouldn't think the speaker itself or wire to it could be drawing power since it should be cut off at the main source? TiA.

 

Someone also asked if I have an alarm in response to my problem and I said I have a Vats bypass kit on it with the three place switch. Is it even possible the bypass switch could be doing it being switched to "on" to bypass it?

 

You need to measure the leakage current by disconnecting the neg battery cable and connecting an ammeter from the cable to the battery terminal. Unplug the courtesy fuse so the courtesy lights won't come on. GM says leakage current should not exceed 50 milliamps. My 87 has 27 ma. of leakage and I have no battery problems. Pull fuses one at a time and watch the ammeter for a sudden drop in current, then further investigation of that circuit will be necessary.
At night look for underhood light on, vanity mirror light on, door map light on, console light on. Do you have a CB, radar detector, aftermarket alarm, or radio, or audio amplifier? Check em. Don't leave your key in the ign sw, this keeps the theft module on.

 

After connecting your AMP Meter on your Multi-Meter in series with the negative battery terminal. With all doors latches shut (use screwdriver, this way you can leave the doors open, to access fuses if necessary) and key out. Leave it sit for at least 1 hour so all the modules go to sleep. Then note your amount of "parasitic" draw on the battery from the reading on the meter. IF you have draw, remove fuses one at a time until the draw goes away. Then look up that circuit in your FSM and then you have to unplug components on that circuit until the draw goes away. FSM should contain detailed instructions on doing this test. IF you do not have one, GET ONE!!!

IF this sounds like a PITA, well...it is. Mechanics (me included) do not work for nothing. We get to put up with this crap all day. We only do it because we love cars and we are borderline psychotic.

FYI, anyone can replace parts and out money a problem. You save money when you figure out the problem and only replace necessary parts. Besides diagnostics is fun.

 

Hmmm, I have a similar problem with my `90. My neighbor hooked up his volt meter to my neg cable/terminal, & it reads 12.5 volts. We pulled every fuse & even pulled the alarm module & ignition switch. Its still there. Are we doing something wrong?

I`m pretty sure he was using the volt scale.

 

You need to disconnect the negative cable and hook meter, IN 10 AMPS range, in series with the disconnected cable and battery negative and wait at least 1 hr. IF it reads anything over 50milli amps you have a draw and need to pull fuses monitoring the meter until it drops. Keep in mind anything you turn on (accidently or not) will cause a false reading. Hook it up and leave it alone for about 1 hr. I recommend you leave doors open but "close" the latches with a screwdriver so the car thinks the door is shut but you can access the fuses for later.

YOU WILL NEVER FIND A DRAW IN THE VOLTAGE SETTING.

 

Thanks