Posted by David Sherman on Thursday, August 09, 2007 at 22:10:36 :
In Reply to: Re: Amp meter is pegged? posted by LinK on Thursday, August 09, 2007 at 20:36:45 :
The "voltage" regulator is supposed to also limit the maximum current to what the generator or alterator can safely put out. In this case, that's presumably 60 amps. It would be nice to check the system by putting a known good ammeter in the alternator output lead to see what it's really putting out, but you probably don't have one. Your average pocket multimeter's only good up to 10 amps. My hunch is that the alternator and regulator are working fine, but they're putting out more than the full-scale rating of the ammeter. This probably won't hurt anything, and the ammeter reading should settle down once the battery's well charged. I would check the battery voltage while the truck's running at high idle to make sure it's not above 14.5 or so, which would indicate overcharging. I've seen old ammeters with ratings as low as 15 amps full scale, and 30 amps seems to be fairly common on old rigs, so it wouldn't be surprising if the only reason it's maxed out is that the alternator is putting out a lot more current than the stock one did.
If the battery's not over charging, I'd leave it, since it would be hard to find a replacement ammeter that looked the same but had a higher full-scale rating. A little extra current probably won't hurt it. There's no difference between an ammeter for a generator system and one for an alternator system.
If the ammeter never settles down to within its range, then I'd start looking for other problems. Something is drawing too much current. A short in the wiring somewhere is possible, but unlikely, since 60 amps going through a short would probably burn something up and make itself obvious. More likely is a shorted cell in the battery which makes it never get up to full voltage. You'd identify that because the battery voltage would be too low (less than 11 volts) even after it's charged for quite a while. Odds are, though, it's just that your old ammeter reads considerably less than 60 amps full scale.
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