I have an 85 Amp alternator on my '57 GMC,and it seems to be overcharging,like 16.5 volts at anything over 600 rpm's. This voltage holds even with every electrical accessory on the truck running.I know the problem isn't related to operating speed because I ran this same alternator for about a month on this engine and it was running within specs,no problems. After it started acting up,I replaced the regulator,same problem. I had the old regulator tested,14.7 volts,just like it should be. I've also noticed recently my radio only makes sound when I rev the engine a little;at idle,it still lights up,but the speakers make no sound until it's running at 750 rpm or more. I was told by the owner of the automotive/electric shop here it may be related to a grounding issue. I have new battery cables,replaced just a week or so before the problem. My ground cable's connected to the top right bellhousing bolt,which I removed the paint from and tightened to about 50 lbs torque. There's a 10 ga. ground from the firewall to the frame.and a ground strap from the head to the firewall. I'm out of ideas. Everything is working fine (except the radio),but I'm worried that if I get on the highway with it,something's gonna go ugly. The battery still starts the truck even at below zero temps,shows about 12.5 volts when I get in the truck in the morning.Voltage goes to 9.5-10 volts cranking.I also noticed the radio falters for half a econd when I turn on the heater fan or use the stoplights. Sounds like a ground to me too,but where?? I don't think it's the alternator case,or it probably would've got either better or worse when I removed/reinstalled the alternator to replace the regulator. Any iseas?
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