voltage fluctuations?

[StorminN]

I've got an intermittant voltage problem with my '83 van, and I hope someone can help diagnose it.

Occasionally, when I drive for an extended period (like 1+ hour) with the headlights on, the voltage indicated on my stock voltmeter drops or become irratic... it can fluctuate wildly between low (in the orange) to high (near the other orange), or sometimes it just stays near the low.

I thought it might be a loose belt, because it sometimes seemed like at high RPM the voltage was lower, and at low RPM the voltage was higher... however the belt had not been squealing at all...
Last week, with the motor idling, I tested the voltage at the battery, and it was 13.2v. After tightening the belt, the voltage was 13.6v with the motor at idle... I thought I had solved my problem.

This past weekend, I knew I was going to be towing my boat to go fishing, and I didn't want to have any problems, so I put a battery charger on the van the night before, and topped off the batteries at the 2 amp setting. Early the next morning, I towed the boat about 2 hours to the launch, the whole time I had the headlights on, and about halfway through the trip, the voltage started acting up... the meter was fluctuating, the lights were dimming, the stereo was cutting out, etc. We got there, launched the boat, came back about six hours later, and the van wouldn't start. I got a jump and it started right away.

This morning, with the motor idling, I checked the voltage at the battery again, and it was 14.6v !!

Until this moring, I thought the problem might be a loose connection at the starter, but with 14.6v, I think it may be the regulator in the alternator... does anyone else have any suggestions?

Thanks,
-N.

[britannic]

Aside from the regulator and ensuring your belts are tightened so that there's only 1/4" deflection when firmly pushed on, go check out all of the negative grounding points on both the engine and frame.

How new are the batteries? Do they load test OK?

[StorminN]

Hi Britannic,

Thanks for the reply!

Ah yes, the negative ground connections... I should have thought of those... how many should there be? This is a van, remember...

The batteries are not new, they came with the van when I bought it a year ago, so I don't know their age. I have yet to load test them, I need to crawl underneath and unbolt the lower one (in the van it's mounted next to the frame rail, below the driver's seat) and I've been too busy working and fishing to mess with it... but I need to find some time this week to deal with it, I've got a bigger trip planned this next weekend.

Thanks,
-N.

[britannic]

I'm not sure about vans, but you could trace from the negative terminals on the batteries and check for those grounds first.

Thne check the engine for a large negative lead bolted onto to it somewhere. For example my engine ground is on the rear passenger side head, bolted to the intake.

The alternators also have auxilliary grounds sometimes, just look for a black wire bolted to the engine coming from the back of the alternator.

[StorminN]

Thanks for the advice, Brittanic... turns out it was the alternator, $90 and I'm back in business.

Thanks,
-N.