Total loss of electrical

[kcsa75]

So after work I start my truck (72 C-10, 350/350). When I turned on the lights, the needle on the tach went to zero momentarily and the light on the radio flashed. I turned the lights off and back on again a couple more times and the same thing happened. Then I put it in reverse, went about three feet and everything died. There was no juice anywhere. Zip, Zilch, Nadda, Nothin.

I looked under the hood and didn't see anything obvious. So I tapped on the voltage regulator and the alternator with my flashlight. I got back in, started right up, and I drove home without a problem. All the presets on the radio were gone, which means it lost all power.

My only thought is the regulator is going bad. But I know about as much about electrical as I do nuclear physics.

Any help would be appreciated.

[Zeke's Garage]

Does the '72 still have an external voltage regulator? 6" square-ish box on the inside of the driver's side core support? I thought all GM vehicles were internally regulated by '72, but I'm wrong all the time...

Check your connections to the battery, starter, grounds to the block, hot wire to the junction block next to the battery, the alternator, and the splice feeding the junction block to the alternator wire (might have to unwrap the harness a bit).

[zeldman]

I had a 70 C-10 that had a problem similar to what you described, only difference is I only had the problem on rainy nights. After 18 years I found the problem, and it is worth a try for you to check.

On the battery, there is a hot accessory wire that goes from the battery to a junction post on the fender close to the batt. There are two eyelets on the wire on that post, dont know why but it is there, check those eyelets. Mine was broken inside the plastic sleeve of the eyelet and had a little corrosion in it as well. So at night, with the radio and headlights on, with rain coming down, I would turn on the windshield wipers and the radio and lights go off and the engine would stop running. I would turn off the wipers and everything worked fine. Sometimes I would get in it in the morning and not have any power at all, like the battery wasnt there. I would check the battery and have a good 12 volts but nothing anywhere else. I would take a screw driver and jump across the solenoid to start the engine and then everything would work fine. After I replaced the eyelets, I never had the problem again. I guess there was enough connection to work but with everything on it would draw more current than the connection could handle. Sitting here thinking, maybe this is why I got a 3 year old truck with less than 50,000 miles for only 700 bucks.

I hope this helps you, and good luck.

[LockDoc]

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You might try unplugging the regulator connector and see if you can clean the contacts or buy some spray electrical contact cleaner and spray it. After you spray it plug it in and unplug it a couple of times. I'm not sure what happens if the points in the regulator stick but that is a possibility too.

LockDoc

[jrdv]

Just had the same problem with one of mine. It was the hot wire from the battery to the junction box. It looked good but had a break in it. I made a new one and I'm back in business.

Hopefully yours is an easy fix.

John