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Q: There appears to be a short causing the battery to drain while the engine is off

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I acquired a 93 k2500 GMC suburban in June of '16. I don't know much about her history. I do know this: There had been an electrical fire in the dash; the wiring harness has since been replaced. The catalytic converter had been removed (poorly) and has since been replaced. A stereo had been installed and various parts removed leaving random wires. I have also now replaced the fuel pump and starter. The only starter that fits is a 98, so I'm assuming the transition had also been replaced. Now I think I have narrowed down the problem to electrical. I apparently have a short somewhere causing a battery drain. If I jump her she'll run, but if I don't disconnect the negative cable when I turn off the engine she won't start. I've checked all the fuses I can find, replaced the broken ones, had the battery tested, charged, jumped, and I still can't figure out what's wrong. Please help before I smash my battery through my windshield!

My car has 191000 miles.
My car has an automatic transmission.

A: Hi there, thank you for asking a question a...

Hi there, thank you for asking a question about your 1993 GMC K2500 Suburban. The easiest way to find the source of battery drainage is by process of elimination. Get a hold of a volt/multi-meter. Start with a fully charged battery. Connect the volt meter to the battery set to 12 volts or higher. The battery should be reading close to or a little above that.

If it’s reading lower, then start pulling fuses one at a time. Pull each fuse long enough to see if there is any voltage change on the meter. Give it 20-30 seconds at least. If there is no change, then reinstall and move to the next fuse. Do this until you pull a fuse that causes the voltage to go up. That circuit will be where you will have to start checking for a short, whether in the wiring or in an actual part.

Considering the fire and wiring repairs, I wouldn’t stop checking circuits with the first fuse removed that makes the voltage go up. Write it down and check them all. There may be more than one blown fuse. If you are not experienced with checking and handling fuses in a car, have a certified technician from YourMechanic come to your home or office to inspect and replace any fuses.

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