Re: Ammeters vs Voltmeters ???

Posted by Hal/WA on December 12, 2004 at 15:23:12 from (148.78.243.24):

In Reply to: Ammeters vs Voltmeters ??? posted by Alberta Mike on December 12, 2004 at 06:19:50:

When my son replaced the old low amperage alternator on his 71 Scout with a much cheaper, later GM internal reg. alternator, we found that the ammeter got really hot (the battery had been fairly discharged). Once the battery was back to full charge, the ammeter never got hot again.

I think that the ammeters in older machines were often wired with all or nearly all of the electrical load running through the ammeter. I suspect that the Scout ammeter was fine for about 30 amps maximum charge, but 60 or 65 really challenged it.

The Scout didn't burn up, but we worried about that possibility when we saw how hot the ammeter got. We put the battery on the charger overnight rather than continuing to charge with the engine. He kept the Scout for another year with the same ammeter and alternator and it continued to work OK, but he avoided situations where the battery would get discharged a lot.

I recently changed alternators on my 84 F250 because it quit charging and the ammeter needle never moved. With the new alternator, the needle still never moves, but the system appears to be charging--the battery stays up and the electric choke opens. I have studied the wiring diagrams and believe that the factory wiring only measures one of the smaller wires to the alternator rather than the whole output like it was on the Scout.

I think I will add a voltmeter below the dash since I can't seem to figure out why the existing ammeter needle never moves. Maybe the dash ammeter is broken or there is a break in the wiring harness or something? A voltmeter would be able to tell me if there is enough charge in the battery to start the truck, which often sits for a week or more without being used.

Follow Ups:

• Re: Ammeters vs Voltmeters ??? ChrisH (IA) 10:34:02 12/13/04 (1)
  • Re: Ammeters vs Voltmeters ??? Hal/WA 21:34:47 12/13/04 (0)

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