Amp Gauge / Alternator Questions

[Feldsine]

Hello all. My truck is a 71 C20. It sat for 15 years, and when I got it running good, the alternator started shrieking. This turned out to be the bearings which probably rusted and gave out. So I replaced the alternator with a Napa Delco Remy 62 Amp 4 wire unit.

When I installed the new one, the belt was apparently too loose even at the far end of the adjustment. That one had belt shrieking, but here is the wierd thing, at the same time as the noise, the Amp gauge would move to the right to the first mark (halfway over). When the noise stopped, the gauge went back to the middle.

So I went to Napa again and got a new belt, and put that on. That took care of the noise and adjustment, but now the Amp gauge will intermittently move to the first mark to the right, maybe hang out there a while, and come back to middle. Most of the time it hangs out in the middle, but every once in a while (every few miles) it starts moving around.

I'm not sure what's up with this now. It seemed like last night, when the amp gauge started going to the right, the lights got brighter too. I'm afraid I might start popping bulbs or something.

You guys have any ideas on this?

[Wrenchbender Ret]

Put a voltmeter across the bat & see what is happening. It should show right close to 14 volts at a little above idle. If it fluctuates & it is an external regulator you most likely have a bad regulator. If it is a internal reg. it probably is defective. The belt squeald when it had a load on it. When the amp. meter came back to center there was no load & the alt was just spinning.

[El Dorado Jim]

I think all of our trucks have an external voltage regulator mounted on the radiator support,in '73 they started using alternators with internal regulators I was told years ago to always change the regulator whenever you change your alternator

[Feldsine]

Thanks for the answers guys, I'll take your suggestions and report back.

[Rich69shortfleet]

Nowadays you have a choice between an original style electro-mechanical regulator and a solid state regulator. Choose the solid state one even though they are typically more expensive. They last longer and are more reliable and switch voltages up much quicker. Also, finding a quality electro-mechanical version can be a challenge.

[Feldsine]

You mean for the external voltage regulator? I didn't know they made solid state external regulators, I'll check into that. Thanks.

[Rich69shortfleet]

Originally Posted by Feldsine

You mean for the external voltage regulator? I didn't know they made solid state external regulators, I'll check into that. Thanks.

They sure do, have for quite a few years. They often look the same though so it can be hard to tell the difference just by looks. I just poked around a bit and it looks like the electronic ones are more common now and typically cheaper. Good news for you!

[Feldsine]

Well, I did get this squared away. I put a voltmeter on the battery and it was putting out about 19 volts. Got a new one from Napa, and it only put out 12.1 volts. Put my old one back in, 19v, Napa again, 12.1. Finally went over to my 69 which I had switched to a one wire, and sure enough, I had left the old voltage regulater there. Took it out, put it in the 71, and voila, 13.5 volts. Took the Napa one back and got my money back and it's been find since.