battery problem

[Kenneth Cole]

Hi
My batteries are being drained just sitting for a couple of days. I noticed that when I take off the negative terminal and touch it to the post I get a spark. I would assume that this is indicating that something is drawing current. This is with everything shut off. Is there something that I am not aware of with the Humvee (1991).

Ken

 

[NDT]

You are quite correct, that spark indicates something is allowing current to pass. Need to employ the process of elimination, disconnect devices one by one until the offender is identified. I would start with the alternator excite wire.

 

[Kenneth Cole]

NDT
Could you tell me which wire that would be?

Thanks
Ken

 

[papakb]

One of the simplest things to use to test this is a clamp-on current meter. Be aware that the majority of them used by electricians are for AC only and you'll need one that measures DC. They sell anywhere from $25 on up. It's a good addition to any toolbox because they're also general use multimeters. With it clamped around one of your battery leads as you disconnect things you'll see the current change and when you find the offending lead you've got your culprit. There will always be a few milliamps of current in any vehicle but you want to identify the high draw path.

Common problems are with the alternator diodes leaking, the PCB, starter, and frayed wiring.

 

[NDT]

NDT
Could you tell me which wire that would be?

Thanks
Ken

The smallest wire of 3 that attaches to the alternator. If this fixes the draw, I believe the protective control box is bad.

 

[doghead]

Guessing it's wire number 10. IIRC

Standard military wiring number.