Parasitic draw on battery, 96 Sierra

[That Crazy Squirrel]

If you disconnect the alternator and the draw goes away, it's obviously a fault in the alternator... To state the obvious.

Not necessarily... That's like saying that if a light keeps coming on the problem is with the bulb.

The black wire he's talking about is the B+ field wire, and it provides a little current to sort of "jump start" the alternator by magnetizing the field windings until the alternator is putting out sufficient voltage and amperage to maintain the field on its own.

That voltage and current comes from the battery, by way of the ignition switch and the alternator gauge. He's already said he was having issues with the gauge, I'm betting those "issues" can be traced back to a problem with the ignition switch, or the wiring to it.

 

[That Crazy Squirrel]

So my truck has been sitting for a while. Put in a new battery since the old one wouldn't take a charge. Well, I've been chasing an alternator gauge problem and during the diagnostic found a parasitic draw. Except it doesn't drain the battery overnight or anything. Yet my draw has been 6 amps and won't go away unless i disconnect the wire from the back of the alternator. I took the alternator up to Autozone, its new and it tests all good. Ideas?

See my reply to Zembonez. Your gauge problem is the cause of the draw, not vice-versa, and your alternator is fine.

Let me know if you need schematics for it, as I'm pretty sure the set I have covers 96

 

[Black02Silverado]

So my truck has been sitting for a while. Put in a new battery since the old one wouldn't take a charge. Well, I've been chasing an alternator gauge problem and during the diagnostic found a parasitic draw. Except it doesn't drain the battery overnight or anything. Yet my draw has been 6 amps and won't go away unless i disconnect the wire from the back of the alternator. I took the alternator up to Autozone, its new and it tests all good. Ideas?

See my reply to Zembonez. Your gauge problem is the cause of the draw, not vice-versa, and your alternator is fine.

Let me know if you need schematics for it, as I'm pretty sure the set I have covers 96

Makes sense. The Electric Crazy Squirrel is the critter!

 

[Wyley87]

I would love a schematic.

I got to talking to the guy and he described my garden issue as normal since the truck slows down when it dips. His alternator tester put the output at 125amps. He also tested for the draw and said the wasn't one. He said there might have been a capacitor charging up the way I was testing.

 

[That Crazy Squirrel]

Shoot... It's 30 PDF files for the complete wiring, so I tried zipping them and it's 1.52 megs. Max size for zip attachment is 200k. I don't think the system will allow me to attach 30 files either.

Here's the ones for the charging circuit and both fuse blocks though.

 

[That Crazy Squirrel]

I would love a schematic.

I got to talking to the guy and he described my garden issue as normal since the truck slows down when it dips. His alternator tester put the output at 125amps. He also tested for the draw and said the wasn't one. He said there might have been a capacitor charging up the way I was testing.

Capacitor big enough to draw 6 amps and hold that draw while you tested? Nah, not in that alternator. No way.

 

[That Crazy Squirrel]

These will help too... Gauges and ignition switch connections.

 

[That Crazy Squirrel]

If you need any of the others, let me know.

 

[Wyley87]

Thanks bud

 

[PenguinLTZ]

Put the meter inline and observe the draw.

One by one, remove the fuses that are on the "battery" side of things, not the ignition switched fuses.

Sine you know have diagrams, you can see which devices, or which relays are on the circuit that is suspect. If the dash is an issue as mentioned, the draw will disappear when you yank the fuse.

Just a quick, easy process of elimination to go through.