1972 C10 350 Charging Issue

[Bryon.Dillon]

I dont know whats going on here, but my battery keeps getting drained to the point where I cant start my truck. I replaced the battery a week ago trying to solve the issue and it seemed to do the trick, until this morning I went out to start it and it didnt have enough juice. So naturally I assume it's the alternator, so I bring it in and have it tested at autozone. They tell me it's good and is charging 14.6v. So I buy a new voltage regulator, and install that in my truck. Heres the weird thing, if I start my truck and check the voltage coming from the red wire on the back of the alternator, its at 12.6v... i get the same reading on the battery, it seems to fluctuate between 12.6v and 13.10v depending on how long i let it run after jumping it. I'm seriously stumped, I have cleaned the battery cables and the ground to the engine. Tested all the wires going from the positive distribution block and they are putting out the same voltage as the batter post. What else could be wrong?

[502ms]

How long have you owned the truck? Are you certain to not turn the key all the way back when you remove the key? Bad habit....
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[Bryon.Dillon]

Nah thats not the problem, thanks though =) also would like to note that there is no stereo installed in this truck, the dome light has been disconnected at the fuse block. I'm going to go through all the fuses tomorrow

[502ms]

I would say there may be something shorted, therefore drawing current...like an antennae, parking light , taillamp...
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[Bryon.Dillon]

with all of the wires going to the alternator disconnected, and the engine running off the battery, what should the voltage be coming from the circled connector?

[502ms]

Trick question?

Disconnected alternator should have 0 volts if not mistaken, as it s not being used to charge if inactive. When driving under throttle, I'd say north of 13 volts (13.8 or so).
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[domeier]

You most probably have a wire chafed to ground somewhere. Until you figure it out, keep your battery disconnected so it won't drain. Quickest way to check is to see if there's a little spark when you hook the battery up with the key off and truck not running. Easier to see at night. If you have a spark, disconnect wires until you don't; then you'll know which circuit is causing the evil.

Kinda hard to explain. Wish you were closer, I'd give you a hand.

[LockDoc]

-
Unhook the + battery cable and connect a multi-meter between the post and cable to see if there is a draw with the switch off. If there is remove the fuses one at a time. Check the meter each time. You only have to pop one side of the fuse up, you don't have to remove it all the way.

LockDoc

[domeier]

Originally Posted by LockDoc

-If there is remove the fuses one at a time. Check the meter each time. You only have to pop one side of the fuse up, you don't have to remove it all the way.

Most of those fuses aren't energized with the key off. I got a dollar says his problem is before the fuse box.

[oldgold70c10]

Does your horn work? I ask because the horn relay is not fused. If there is power to the relay, it will drain the battery. Unplug the relay under the dash. If you hear it click, you know it was drawing current. Other than that, there are only a few things that are hot at all times thru the fuses. The 3 15A fuses labeled Traffic Hazard, Tail Stop Dome, and Gl. Box & Spot Lp. Are the only ones hot with the key off.

[Bryon.Dillon]

Thank you for all this information, I will check out some of these solutions when the weather leats up. Unfortunately I dont have a garage =( I will update you with what I find

[Bryon.Dillon]

also the truck seems to be holding at 13.10v while running after I changed the voltage regulator. Is this good enough to keep the battery charged?

[domeier]

Originally Posted by Bryon.Dillon

also the truck seems to be holding at 13.10v while running after I changed the voltage regulator. Is this good enough to keep the battery charged?

Yes, that's good. Good luck.

[LockDoc]

Originally Posted by domeier

Most of those fuses aren't energized with the key off. I got a dollar says his problem is before the fuse box.

I am fully aware of that... unless there is a short in the switch.

LockDoc

[Bryon.Dillon]

Originally Posted by 502ms

Trick question?

Disconnected alternator should have 0 volts if not mistaken, as it s not being used to charge if inactive. When driving under throttle, I'd say north of 13 volts (13.8 or so).
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No, with the engine running the alternater should be producing electricity I assume?

[VetteVet]

Originally Posted by Bryon.Dillon

with all of the wires going to the alternator disconnected, and the engine running off the battery, what should the voltage be coming from the circled connector?

Unless it's a permanent Magnet rotor you won't get anything out of it no matter how fast you spin the engine.