electrical issue--tips anyone?

[Busted]

Hey y'all,

Been having problems with the '97 van draining the batteries, so I took both out to check things over--noticed when i connect/disconnect the + battery cable, I get sparks off the post. This is with the key removed, and all switches (lights, heat, etc) turned to "off."

First step was to remove the fuses one at a time to determine which circuit was drawing power. I removed all the fuses in both the inside and under hood boxes without stopping the power draw.

Here's where I need some advice. It seems to me that this indicates the draw is between the battery positive terminal and the fuse boxes, most likely a damaged wire grounding out somewhere?

I'll be working on tracking wires today, but there's not much space under the van hood or under the doghouse--any clues as to the wire routing to save some time?

Also, there is a small black box above the accelerator pedal that clicks when I touch the battery cable to the post--the p/n is 15150325 (instrument panel dimmer module?), should it be getting power with nothing else in the van turned on?

Thanks all . . .

[JTodd]

How were you testing the draw while pulling the fuses? A shorted hot or ground will blow a fuse, so it is more than likely a stuck switch or relay. There will be some draw with key out for the radio and computer. I think .5 amp is acceptable.

[Busted]

I was testing the draw by putting the + battery cable onto the post, it would spark a bit as I did so, and that little black box would click.

What I'm proposing is that if a hot wire grounds out before it reaches the fuse from the battery, it will not blow the fuse and removing the fuse will not stop the draw. OTOH, any hot wires from battery going to fuse block should also melt/blow a fusible link if shorted?

Good tip about the radio and computer, I'll check actual amperage draw next. I'm accustomed to mechanical/carbureted vehicles, which should have ZERO current flowing with the vehicle switched off. Does this mean that if parking the van for more than a few weeks, the batteries should be disconnected?

[JTodd]

Put an ampmeter between the positive terminal and positive cable to measure the draw. I have never done it on my diesel, so you may need to disconnect one of the batteries completely, then use the meter on the other. Make sure the key is out, and all dome lights are off. See what it is as a baseline, then start pulling fuses to see what changes.

[TAG]

You will get a spark when you hook up later model vehicles due to capacitors recharging & some circuits that have a timed power down. Only real way to test is as has been stated, ampmeter between battery cable & terminal. After you hook it up, wait a minute for all the circuits to time out, then you should be reading zero unless you have a really sensitive meter.

[rhsub]

Here is a condenesed version of GM's parasitic load test
Rig up a way of installing an amp meter between bat + and cable, if you have dual post bat this is easy, if not install a 3/8 stud in the + bat post, secure a jumper wire with a nut then install + cable, make sure you do this on the bat that supplies the accessories
Drive vehicle and turn on and off all accessories
Turn off engine and all accessories remove key and close doors
Install amp meter between jumper wire and + cable, 10 amp setting on meter
Disconnect + cable from both batteries. DO NOT OPEN CIRCUIT THROUGH AMP METER
Check meter, if reading is below 1 amp switch to lower scale on meter
Acceptable load is calacuated as follows. Reserve capacity of battery divided by 4 = milliamps ie 100 reserve divided dy 4 =250 milliamps X 2 batteries =500 milliamps approx
If above this, start disconnecting circuits till you find the one giving you problems
If draw is alright check your batteries, one bad battery will kill a good battery fairly quickly or check for intermittents, they are usually fun to find :confused:
Good luck
Ron

[Busted]

Perfect, that's exactly what I needed! I'll let you know what I find out . . .