Your battery voltage is low, and the alternator is charging it up, which causes lights to surge when revved up. The question is, at idle, can it make 13.8 - 14.2 volts - if not, part of alternator (one phase) is not putting out. If you don't have a working meter, let auto parts store test alternator/battery in car. An alternator will take a long time to charge up a mostly discharged battery. Chris-Bob is also right, bad connections on the battery terminals, the two big wires in the under hood fuse box, the main ground (follow negative wire to chassis), and even the 100 amp fuse in the fuse box can also play a role, and rob the system of voltage.

 

I was finally able to get to the auto store to get the battery and alt looked at. The batter is charged and the alternator is charging it, but the alt is jumping between 13.5 and 15.6 volts. It jumps like crazy.

Any thoughts on that?

Is it the voltage regulator? Is there anything else that could be causing this?

At least I can drive it!

Thanks,
Jason

 

Bad voltage regulator, failed "shorted", instead of open. Suggest you have your original repaired if you still have it, or repair with parts listed in the previous link. Most alternator/starter/generator shops will do this for under $100 carry in (including parts).

As to driving it - would not do that - the higher voltage will damage electronic modules in the vehicle. In most cases, you don't need to have something turned "ON" for the voltage to being doing something on the circuit board, they are powered up and just waiting for you to push a button, etc.

 

One more note: If alternator test was performed in the vehicle by the parts store - you could also have a bad ground wire connector between the frame and the engine block. On my D1 this is back by the starter. To test for that possibility, use a voltmeter, and read between the negative (-) battery post and the metal frame of the car. Repeat test between (-) battery post and the engine block. With engine running. Readings should be the same, and very, very small, fractions of a volt if at all.

Had a loose ground on a pickup truck, volts went up to 18 or 19, smoked three very expensive Motorola 70 watt mobile radios.

 

I have a similar problem with my beloved '95 County LWB classic. In the last few days, the battery light will come on, the tach stops working, and the lights dim (if at night). 10 minutes later, the problem will stop, light off, tach working, lights full bright. 5 minutes later, repeat the problem. I'm getting enough from the alternator when things are working to charge the battery, apparently, because so far it starts great. BTW, this is a GREAT forum, and several of you are wonderful educators. thanks! I will try the fixes mentioned here. I have a Bosh AL9347X alternator, it's got 198,000 miles on the car.

Thanks, John

 

Find local alternator / starter rebuilding shop, it will be a small place. Should run about $100. DOn't buy reman unit from big box auto parts, they have high failure rate.

 

BUZZ: Thanks for the link on that voltage regulator, it's going on my list of things to buy soon.

 

It is a fine looking hunk of silicone, err silicon... too much Hooters..

 

I must share i took my marelli magneto to a local trusted alternator rebuild place and though they returned me a clean alternator, and charged me 150 bucks, but also when i brought it back, they measured 13.4 volts across the terminals of the battery, but it took a woman from checker to inform me it wasnt putting out any amps to charge the battery, so i bought one from Eagle Salvage on ebay in california and it was here in 2 days and solved all my problems, lights dimming, windows stop working, etc...

 

Tony, do you have a link to their web page or e-bay store?