swifty777

Ok, I think I already know what's wrong, but I'll ask anyway. Recently got a 71 BB coupe that had sat in storage MANY years. I'm troubleshooting a short to ground that is just not been easy. In fact, have also removed all the fuses and ALT too and is still shorting to ground. I should mention that the Ammeter gauge needle is pegged "hard over" to -40 and has never moved. I'm also doubting the ALT's abiltiy to recharge the battery when running. The question is, can an Ammeter gauge short internally even with the ALT disconnected? If it is shorted, will that prevent the ALT from recharging the battery? If a larger thatn original output ALT was installed when after-factory PW's were installed should the gauge be more than -40 to + 40??? Thanks for any suggestions! :confused:

442olds

Have you tried just disconnecting the ammeter to see if everything works normal without the ammeter in the loop. the range of the ammeter shouldn't matter. When it pegs it won't ground out. This is why I am a firm believer in volt meters over ammeters. Volt meters never have high currents passing through them.

swifty777

Haven't tried that yet, that was the next logical move. Still concerend that the gauge is somehow responsible for return current back to charge the battery is not happening because of the guage soemhow? I'll disconnect and see if at least I can get the short/groung resolved. Thanks for the response
Swifty-

stpman

I would check a wiring diagram before removing the amp meter from the loop, if it is a true amp meter it will be wired in series however most amp meters are actually volt meters measuring a voltage drop across a calibrated resistor (bus) as the meter movements will only tolerate 0.05 Amps through the windings.

Steve :steering:

mrvette

The ampmeter in early sharks, like my '72, is wired in series with the alternator sense wire, the red or black one on the two wire prong, if you are checking with the ignition in the run mode, just crank the car and see what happens.....I highly suspect you are getting a false reading....

obviously check the battery voltage with a DVM, and see where is any voltage losses occurr....see if when the ignition switch if off, battery connected, that you have 12 volts...battery voltage on the output stud of the alternator....if not, check at the horn relay--power distribution point on the dirver's fender liner....

GENE

swifty777

Thanks guys, here's what I've got. Found the culprit stealing me of precious amps........the horn contact inside the car was shorting out, duh........
The Alternator checks good on the bench, 14 volts coming out. I have 11.6 volts with the engine off at the stud on the alternator, at the horn relay contacts and at the battery post too. I have a new battery that has been charged but still cannot start the car. I have to jump start each time, works good after that. The gauge is still something that will need to be replaced. It's pointing at -40 and has never moved. If that is wired in series, will that prevent the battery from receiving it's charge from the alt?
Thanks :banghead: