2001 GMC 2500HD Battery Depletion

toored · April 14, 2020

Truck: 2001 GMC 2500HD, 8.1L/Allison, Crew cab, 4X4, 165K Miles.

Something electrical is dragging my battery down. It usually takes about 3-4 days to deplete it enough where it won't start. The battery is fairly new and I've had it tested by O' Reilly and they say it's good (is their battery tester machine generally reliable?).

I have hooked an ammeter in line with the battery cable and something is drawing 4.5 amps continuously with the ignition off. I have pulled every fuse, circuit breaker, and relay I can find to no avail. I have also disconnected the aftermarket stereo and amplifier from the truck to rule those out. Nothing seems to be out of the ordinary while the truck is running.

I'm at an impasse. I'm not sure what would draw 4.5 amps consistently with the ignition off. I've owned this truck for 14 years and have never had any electrical problems.

Any help or feedback/advice would be greatly appreciated.

MORSNO · April 16, 2020

I'd look for things that work without the key in the ignition, things like brakes/brake lights, dome lights, map lights, power seats/mirrors, etc. 4.5 amps is a lot, so I'm not sure.