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Not Charging, running out of juice - Electrical

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ucnu112

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Here's the lowdown - '87 K5, 350 fuel injected, new engine installed in January. Removed AIR and A/C upon reinstallation. I finally got it running properly (TPS wasn't seating properly, would die when putting into gear), but the electrical system isn't charging properly. I had it out, driving around for about 20-30 minutes and realized too late that the Volt gauge had been constantly dropping. The truck died and would no restart; it acted like there wasn't enough juice to turn it over. I had a voltmeter handy, and it read 11.8 - 11.5...something around that number. Wouldn't start for anything. We tried jumping it off of another car, and it would start, but as soon as I removed the jumper cables, the truck would die.

The alternator has been tested 2x, once at an Autozone and again at a Napa. The starter and solenoid are new. I have replaced the fusable links near the starter. The battery (Red Autozone version) was replaced recently and seems to be holding a charge well. I had bought a new battery in January/February and returned it in April when it would not hold a charge. I don't know, but maybe my problem is killing batteries too.

Could this be caused by something wired up incorrectly during the engine installation? I posted this thread a little bit ago, but didn't get any answer. The truck runs with that wire as a positive, negative or disconnected. I'm stumped... any thoughts?
 
Kind of hard to tell from that pic, but it looks like the ring terminal that should go on the stud on the back of the alternator.

What's the voltage at the battery and at the alternator itself when it will run, if you can check it?
 
It was a ring terminal when it started. It fits on that stud, but if I run the voltmeter between it and a ground, it shows 12V on the voltmeter. If I probe from it to positive, it shows 0. That's why I wasn't really sure where it's supposed to go.

I'll test the voltage tonight and report back.
 
11.71 - (at the battery) before I tried to start it. I haven't touched it died on me.
11.53 - (at the battery) after I tried to start it, the start turned, but didn't have anywhere near the power to turn the engine.

As soon as my trickle charger works for a bit, I'll try again to start it.

edit: the ground on the alternator bracket was loose - I just put a new bolt, washer and nut on it. That didn't help, but it didn't change things either. Just for fun, I tried starting w/ that ground disconnected and it still acted like it had no power. The battery is at a full 12V.
 
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You may want to search for wiring diagram posts, although I'm unsure if it's there or not.

If I'm not mistaken, that's the wire that actually charges. On our trucks I believe it runs up to the junction block on the firewall, which in turn splits to the fuse panel and the starter solenoid. But the wiring diagrams will be authoritative on that.

You said it USED to be a ring terminal, was it loose on the alternator prior? I had that problem on mine, it ended up melting the insulation on the terminal, which meant the alternator didn't work. Big pain, ended up swapping alternator cases.
 
I've got a Chiltons, but it didn't show me what it was for. As for it's previous life as a ring terminal, I only trimmed out part of the terminal so it would fit a couple different places to try and figure out where it works.

I tried again this morning before work to start it. 12V, and hit the starter once and it just drops down to nothing. It can barely turn the starter and has no chance to start the truck.
 
Shot battery will do that.

Chiltons and to some extent haynes wiring manuals are worthless.

Like I said, plenty of posts here (one of mine for example that is solely links to wiring diagrams for the trucks) that are actual GM wiring diagrams. Yours is likely to be wired the same as any truck year prior to yours.
 
If it's a shot battery(it sure seems like it is), there's a bigger issue. I bought a new battery in late January, and went through very similar symptoms. The current battery in the truck is the replacement to that one. I swapped it out about 2 weeks ago. Seems to me that something is killing the batteries.
 
You can measure for draw with a multimeter, not a bad idea if you suspect something draining the battery.

There are also posts about how to do that, it does come up fairly often.
 
this is just a thought, but i had the same thing happen on my 85 3/4 ton sub, when my pulleys glazed over and my belt slipped. it didn't make any noise and it only happened under load. i paid around $100 per alternator 3x from 3 shops each time cursing the previous alternator rebuilder :doah: before i installed a new fanbelt. $9.00 problem solved.
 
I'll check that too - I've watched the alternator spin, and it doesn't seem to have any problems.
 
I would remove and clean all grounds. Somtimes I looks fine but has a layer corosion.
 
13lazer said:
this is just a thought, but i had the same thing happen on my 85 3/4 ton sub, when my pulleys glazed over and my belt slipped. it didn't make any noise and it only happened under load. i paid around $100 per alternator 3x from 3 shops each time cursing the previous alternator rebuilder :doah: before i installed a new fanbelt. $9.00 problem solved.
Click to expand...

Bingo - that did it. I pulled the old belt and the pulleys were shined up real nice! I'm still searching for the happy medium where the belt won't squeal, but at least the truck is functional. Thanks a bunch everyone!!!:bow:
 
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