puzzled
 

I have a 29 coupe pretty much stock with 6V pos. ground electrical system. I got it running and noticed that the amp meter showed hardly any charge at all when I drove it so I tried with the moveable brush and got it to register a couple of lines on the plus side. Not so sure as it sits at about two lines neg. when everything is off. I had a couple of 6V neg. gr. alternators and installed one. If I wound the engine up a bit it would eventually put out some pos. reading. Not so much without spinning it to get it excited. Today, after having not been driven for a couple of weeks I went for a test drive after some brake adjusting and when I started the car it fired right off. Not into the plus side without revving it a bit, then it seemed happy and I drove a few miles and noticed the ammeter was back at its normal spot about 2 lines down. Turned on the lights and it went down several more lines and no amount of revving would bring it back up. It appears the alternator has quit functioning. I'm no electrical guru but have two other A's with the same set up and when I start them up they immediately begin to charge for a few minutes and then rest a line or two + after the battery has regained what it spent cranking. Where do I start to look? Don't want to put another alt. on there and have it die also. All are using the same size two inch pulley.

Re: puzzled
 

You can’t put a neg ground alt onto a pos ground system. Can’t imagine what it would do.

Re: puzzled
 

Misspoke, pos. gr.

Re: puzzled
 

How old is the Battery?

Re: puzzled
 

It's a grey Optima 6V Pos. Ground of unknown age. My understanding is that the car hasn't been driven in years, but this battery seems to hold a charge and kick the car over fine, even after sitting for a couple of weeks. It may have been put in recently as the car was changing hands. The real answer is I don't know. Everything seems to be working, though it hasn't set long since this only occurred this early afternoon. I'm not good at trouble shooting alternator problems. A dunce really.

Re: puzzled
 

Take the alternator to an auto electric shop and have it bench tested. They will be able to diagnose your problem. It certainly could be you need a new regulator. If so, be sure to ask them to install a regulator with the lowest rpm required to excite the alternator.

Re: puzzled
 

Voice of experience here:

Be sure to tell alternator tester person (the actual person doing testing) that it is a 6 volt Pos ground alternator.

Most auto parts stores do not know what POS ground is or that hooking up wrong will destroy regulator inside alternator.

They most times hook up as industry standard 12v neg ground and smoke regulator. Same thing that happens if they switch polarity.

Re: puzzled
 

Good Morning...I wonder if the connections on the back of your amp meter are loose? It might be worth a look. Ernie

Re: puzzled
 

Re: puzzled
 

Take some voltage readings with car off, car idling, and revved up. Let us know what they are and we can help you troubleshoot it.

Re: puzzled
 

Put the spare on and it appears to have solved the problem. Thanks for the sage advice.
The dead one goes back to the builder when I get a free weekday. If he tells me something outside of the alt. caused the problem I will quiz him on what to look for and how. Thanks again.

Re: puzzled
 

Not quite so good. It ate up the spare also. Must be wiring in the car.

Re: puzzled
 

Are you positively sure those were positive ground alternators

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Re: puzzled
 

Freshly built. First one lasted a month, mostly sitting but started the car several times and drove it to get it warm maybe six miles each time.Searching the electrical wiring today for some erroneous stuff there. Seems to me if it happened while driving it has to be the light switch or brake switch, but what do I know?

Re: puzzled
 

Hang in there you'll find it

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