Join Date: Mar 2002
Location: Austin, TX, USA
Re: Heavy draw on my battery
Get a test lamp. The most common type look like a screwdriver with a clear handle and a pointed bit and have a short piece of wire with an allegator clip on the end. You may have to engineer a way to connect it up since the bit don't bite and the aligator clip is likely too small to clip onto the post. A little enginuity will be needed.
Disconnect the negative cable, and insert the test lamp between the clamp and the battery post. Your electrical drain will illuminate the light but the current will be greatly reduced. Next, start pulling fuses, disconnecting devices, and separating connectors until the light goes out. Once you find the offending fuse, device, or connector, you should have narrowed the problem down and hopefully identified the root cause of the drain.
Be aware that the dome light will draw enough to illuminate the test lamp. Either close the doors or pull the dome light fuse as one of your first steps.
Heavy loads are often caused by shorted diodes in the alternator, so it's worthwhile to disconnect the alternator leads as one of your troubleshooting steps. Don't let the red wire touch ground though, since it's hooked straight to the battery source.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI