LT1 Parasitic Battery Drain

**shilohpsu** · 12-23-2006, 09:03 AM

I have a 94 firebird formula with 83k miles on it. My car started to have a slow battery drain - it would be dead if I didn't use it for a few of days. The drain slowly started to get worse and would now drain a normal battery after a day. I started to become annoyed and bought the optima red top. This worked for a while as long the car did sit for days. Well the drain eventually won the battle and will now tear through a red top in under a day.

I got tired of jumping my car whenever I wanted to use it and took it to a dealership. They hooked it up to a computer that tested for a parasitic drain. The test said that it wasn't coming from any of the stock systems. I have added many electronics and disconnected everything I put into it one by one and it doesn't seem to be coming from my aftermarket electronics.

After trying everything that I could think of, I busted out the voltmeter, hooked it up through the negative terminal (like a test light) and started pulling fuses and relays one by one. The ohms maxed out and did not drop when I pulled all the fuses.

Has anyone experienced or heard of a problem like this? For a drain this strong, wouldn't it have to be something with a high amp draw such as a starter? Any advice will help.

Craig

**Z27** · 12-23-2006, 10:06 AM

I have had the identical problem. Always a bad feeling to walk out and push the door unlock button and nothing. I tried isolating it bit by bit and couldn't come up with anything. About the only thing left was the alternator. Took it apart and found a bad diode in it. Diode only allow electricity to flow in ione direction. If one shorts it will drain the battery when the car sits. Borrow one to test it if you can.

**shilohpsu** · 12-23-2006, 10:36 AM

Thanks. I will definitely check out the alternator. I hope that this is the problem, but I am still skeptical. Did you have diagnostics done by a dealership/hook your car up to a computer to find the drain, or did you just discover this the old fashion way? I'm only asking because isn't a drain through the alternator something that the parasitic drain test (performed by the dealership) should dectect? Did your alternator still work properly even when the diode was shorted? I am willing to try anything to fix this problem and will disconnect it to see if the drain continues and test it with a voltmeter. Thanks for the advice and this does offer me a little hope when I thought there was nothing left.

Craig

**Z27** · 12-23-2006, 12:08 PM

I have done my own car maint since old enough to pick up a wrench to help dad and a career in computer repair at the component level. I eliminated miscellaneous circuits draining the battery because I don't want to spend unneccesary bucks either. I have rebuilt a few alternators over the years when the store bought ones wouldn't last. The truck I had the problem ran fine once jump started. Watching the voltmeter in the dash the needle would drop below normal at idle. Expressway driving the charge showed ok. Air conditioning or headlights on really made it drop, as well as rear window defogger.

**Chad97z** · 12-24-2006, 05:31 AM

To determine which circuit your electric drain is on,

1. Turn your voltmeter to measure current rather than volts or resistance.

2. Turn off the ignition and any accessories and close the door.

3. Leave battery connected.

4. With everything off, remove 1 fuse and place the leads of the current meter in series with the fuse contact points in the box.

5. If you observe a current on the fuse jack, that is the circuit that is causing you trouble.

You can further troubleshoot by determining what appliances are on that circuit in the Haynes book.