1994 GMC Sierra 1500 is eating batteries

[RollTidenIA]

Hey fellas.. Sorry to revive such an old thread, but I'm at wits end trying to solve a problem and Google led me here... Don't know why I haven't found my way here in the past!!

Problem: 1994 GMC Sierra 1500 2WD 4.3L Vortec is eating batteries when sitting for more than a day or two.

I disconnected the neg batt cable and put a multimeter in line between the batt and cable. WAS reading ~37mA with key off. Pulled every fuse in fuse block one at a time, but never got more than 3-5mA on two of the fuses. Also disconnected the positive alternator feed. Still no change in the draw with the key off. Put everything back together after charging the battery.

Tore into it again several days later and now I'm showing over 200mA draw with key off. Pulled fuses again, but still no drop in the draw. Pulled starter to check connections there. Even with starter disconnected, still 200+mA draw with key off. Disconnected Alternator again and still no change in the draw.

Where else can I check for the draw problem? The truck still runs great even after 239k miles, but getting it started is becoming a problem.

Thanks ahead of time for any ideas...

CJ

[mudseeker]

check your interior lights such as the glove box?

[silverhairdeere]

it's better to use a 12 volt test light , then do the fuse thing , when the light goes out , run down the wires on that fuse , have you checked for brake lights on all the time , mine was a misajusted brake switch , drove me nuts .

shd

[RollTidenIA]

Originally Posted by mudseeker

check your interior lights such as the glove box?

Pulled the interior cab light bulb out of its socket. Not sure if my glovebox has a light or not - I'll check that this evening.

There are 3 different wires coming off of the positive battery post. They are still all clamped/housed in the original factory batt cable connector. Anyone know where those 3 different wires go? One to starter, one to alternator, one to main fuse block? I'm considering hacking the factory batt cable tonight so I can isolate each wire and see which area is actually pulling the draw. I hate hacking the original clamp, though. Open invitation for future corrosion I'm sure...

[RollTidenIA]

Originally Posted by silverhairdeere

it's better to use a 12 volt test light , then do the fuse thing , when the light goes out , run down the wires on that fuse , have you checked for brake lights on all the time , mine was a misajusted brake switch , drove me nuts .

shd

Haven't noticed any lights on at night, but maybe the switch is out of line enough to draw a little, but not enough to light up the bulbs? I'll check that tonight..

I'll pick up a test light at the hardware store on the way home.

I hate electrical problems...

[leolkfrm]

try moving the ignition switch and see if the draw changes

[Harper]

Check all interior lights and make sure they all turn off when u want them to. Also try putting a switch on the neg. battery wire. Doing this with save yr battery but the down side is that you will have to turn it on and off everytime you drive.

[Flopeyeman]

Be sure to check the light inside the glove box, I had a similar problem that drove me nuts for dang near a year!!!! the switch inside the glove box had shorted out and the light stayed on!!!

[crabtruck]

Welcome to the forum CJ.

You shouldn't have to hack the batt clamp.
Disconnect at alt first, and if that doesn't end the 200mA,
unbolt at firewall battery junction block (row of bolts, prob just psgr side of center)
Given your earlier results with alt and starter not changing things,
this is prob the best place to divide the question.

That should give you a break point in the wiring without any damage.
If those two are disconnected, then look to starter hot.
Best to hunt the problem while seeing the 200mA draw,
there are acceptable reasons for little draws.

[RollTidenIA]

Originally Posted by crabtruck

Welcome to the forum CJ.

You shouldn't have to hack the batt clamp.
Disconnect at alt first, and if that doesn't end the 200mA,
unbolt at firewall battery junction block (row of bolts, prob just psgr side of center)
Given your earlier results with alt and starter not changing things,
this is prob the best place to divide the question.

That should give you a break point in the wiring without any damage.
If those two are disconnected, then look to starter hot.
Best to hunt the problem while seeing the 200mA draw,
there are acceptable reasons for little draws.

Thanks for all the tips folks. Even if I don't figure it out, I'm always learning something new.

Ok.. New info for a diagnosis. If I disconnect batt from the junction block under the hood (mounted on pax side of firewall) AND the alternator, my draw drops to about 50mA. If I touch EITHER the junction block connection OR the alternator connection to their respective posts, the draw off of the neg. batt terminal jumps to over 200mA.

Does that help things or just muddy everything up more?