Battery drain 2009 chevy shortie

[Speedseth]

Hi all!

I’ve got a 5 window 2009 Chevy (3500 van body) shortie, and it’s experiencing pretty fast battery drain as I work on it in my driveway. Because it’s a tight fit, I almost always enter through the rear door or passenger entrance. I know that you need to close the drivers door after using the headlights- otherwise the dash & dome light stays on.
The bus was previously used for 2 years transporting cast and crew during Covid for movies. It sat in a lot and was unused for weeks at a time. Started right up- when I checked it out (I was able to look at it a few times at my leisure over a month- owner was not secretly charging the battery)

Currently I’m experiencing a drain with no apparent lights turning on as I work on the bus. My best guess is that it’s connected to having either the rear door or passenger swing door open. But with no apparent lights turning on, I can’t figure out what would be causing the drain. My googling hasn’t found anything and I’m at a loss. Any thoughts?


P.S. I also have a zonar fleet management system and. a check-mate student safety thingie. Both appear to be disabled. Figured I’d mention everything I could think of.

[Jolly Roger bus 223]

do you have a multi meter and know how to use it?

[Speedseth]

I do not. But I’ve got a friend that I’m calling in a favor for help (in the next couple weeks).
I was hoping this issue was somewhat common amongst van chassis buses and there might be a common answer. Otherwise, it’s hang tight for the friend and the multi meter….

[PhilipE]

Unhook the alt main output wire and see if the drain goes away. Over my many years working on vehicles. I found the GM alt were prown to blowing a diode and discharging back threw themselves.

If your meter guy shows up. Disconnect the main power wire from the alt. Test on OHMs. Test from ground to the main power terminal. If any OHMs are shown. Replace the alt.

Over the years I found that each OHM shown on that test would equal 1 amp discharge rate.

[Speedseth]

Thanks a ton. My meter guy is coming over in 5 minutes. Great timing!