Alternator Pushing too many amps, Replaced and still too much amp


Jul 24, 2007
I have a 1975 Firebird, 400 engine. Yesterday I drove the car around, stopping and starting a few times. In the evening, the car would not start, was dead. I jump started the car, and drove it 2 miles to my home. During the drive I realized the AMps showed 18 on the gauge, and the interior and exterior lights got brighter as I accelerated. I got the car home, assumed it was the alternator, removed it (it was very hot), and replaced it. I tried to start the car today and it was the same, dead. Hooked up a charger, battery shows full, tried to jump it and as I tried I saw the amp gauge go to 18 amp, so I shut it off. My battery is 2 years old, and the cables are tight. Any idea what might be a problem? Can it be the starter? would it show too many amps? Also, the only other factor is that I replaced the radio a few days ago. I put in a 200w radio, wired it red to red (inginition has a 75 fuse in it), and yellow to the yellow battery for the clock. The yellow had a 1amp fuse, it blew a few times so i had to use a 10amp. this is just for the clock and radio memory. Only other thought is that I may have disturbed wires under the dash, or maybe not grounded the radio good enough. I woudl appreciate any help or ideas. Thanks, Dan


Sr. Member
Nov 21, 2006
The dash guage reads volts not amps & they are not very accurate. You need to use a multimeter [voltmeter] & check the voltage at the battery with engine running. It should read 13-14.5 V. If the voltage is too high make sure that the alternator is grounded by testing for a voltage drop between the alt. housing and the engine block. To check the battery best way is to disconnect the cable overnight. then if the battery is dead you know you have a bad battery.



Thanks, and yes Volts.... I screw up the terminology alot. I did unplug that battery all night, and it was fine today. I am very curious about the Alternator Ground. I think I may not have grounded it of the ground post on the alternator body, because the one I took off wasn't. Maybe the old one had a wire bust off, and that is what caused the issue in the first place. I know I did not ground the ALt. , I will go do that now, and see if that helps. Thanks!


10SI with the 1-2 plug, sounds like your alternator besides potential ground problems is in secondary regulation mode that runs in the 18-20 volt range. The cause is corrosion in the Packard Electric female spade terminal not making clean contact to the voltage regulator #2 terminal that senses the battery voltage. No contact here, bang, you are in secondary regulation. These contacts tend to turn green and are unplated brass. Can be removed from the housing with a tiny screwdriver, wire brushed and coated with dielectric grease. If the #1 contact is also dirty, your alternator won't start up. You have the same connectors on your HEI, check those too, GM used these for years, and was a constant problem, an unplated connector in an open housing, no grease, and exposed to the elements.

The #2 alternator pin is a dry circuit, (no current flow, just the voltage is felt) so is a common problem area.