Dead battery
Thread Starter
Intermediate
Joined: Apr 2005
Posts: 25
Likes: 0
Dead battery
I have an 1988 Coupe, replaced my battery last week and something keeps draining it. There's not any type of aftermarket devices on the car such as alarms, stereo amps or remote starters. Any suggestions? Thanks
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
Remove a battery cable and connect an ammeter between the cable and the battery. If all is ok, current should only be a few milliamps, but in your case will probably be more. Pull fuses one at a time to see if you can identify the circuit that is drawing power. Then you need to troubleshoot that circuit to see what's wrong.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Steve got a good start for you. But just a couple things to keep in mind. Make sure the interior and hood lights are going off.
Also a possibility the alternator is causing the drain. Check this if nothing comes up with the pulling fuse effort. You would need to remove the cable to it and then make the currnet measurement again.
Also a possibility the alternator is causing the drain. Check this if nothing comes up with the pulling fuse effort. You would need to remove the cable to it and then make the currnet measurement again.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Two things to look for that may be easy solutions is to check the console lid for the light staying on. Another is for the lights in the sunvisors staying on. You should be able to see these lights glowing in a dark garage with a door window down.
Checking for a current drain can be done with a digital voltmeter that has a milliamp setting. Disconnect the underhood lights and shut the car doors, making sure that the interior lights are off.
Disconnect the negative cable and connect the DVM leads with one at the cable and the other at the battery terminal. Set the DVM to millamps and look at the readout. You can then remove one fuse at a time and watch for a drop in the reading. If you see a drop, that is the circuit that needs to be checked. Sometime a sticking or bad relay can cause a current drain.
Checking for a current drain can be done with a digital voltmeter that has a milliamp setting. Disconnect the underhood lights and shut the car doors, making sure that the interior lights are off.
Disconnect the negative cable and connect the DVM leads with one at the cable and the other at the battery terminal. Set the DVM to millamps and look at the readout. You can then remove one fuse at a time and watch for a drop in the reading. If you see a drop, that is the circuit that needs to be checked. Sometime a sticking or bad relay can cause a current drain.
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
Remove that bulb, then test the amperage draw at the battery as suggested above. This could well be your problem. A light bulb is actually a controlled path to ground.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
You can also just replace the bulb and see if it lights (when it should be off). If it does, you might have found the problem. If it does not, then that melted area might be from normal wear and tear over the years.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
GM says leakage current should not exceed 50 milliamps. My 87 draws 27 ma. and I have no problem with the battery. Don't leave your key in the ignition because this keeps the antitheft circuit on and discharges the battery. At night look for vanity mirror light, underhood light, door panel lights, console compartment light, storage compartment light. Do you have a GPS, radar detector, or anything plugged into the cigarette lighter? Check em.
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