Expert: Brad Sears - 11/8/2010

Question
QUESTION: My 1962 Pontiac Bonneville is not charging. I have taken the
alternator and regulator in to be tested, they both are
working correctly. I do not have the correct voltage at the
battery when running and the car dies when I remove the +
cable. The car also dies when I remove the wires from the
voltmeter. Is there a fuse some where in that system and can
you tell me where that might be found. Any help would be
appreciated. Thanks, Al

ANSWER: There is no factory installed fuse or fusible link between the battery and the alternator. However according to all of my manuals the 1962 Pontiac was equipped with a DC generator and alternator were not used until 1963. If I am wrong please let me know. But if it is a replacement then I would need to know the make of the alternator to diagnose the problem. The alternator that was used on the 63 had 4 terminals on the back. Two were stud type and two were spade plug in type. One of the studs was POS and the other Ground. The plug ins were Field and Relay. If this is the alternator the POS terminal should have voltage to it all the time. If not run a 10 gage jumper wire from it to the POS terminal on the battery. If you have a voltmeter hook it up across the battery. Start the engine and the voltage should climb to 13 volts or more. If there is voltage at the POS terminal of the alternator the check the F terminal of the alternator. It should not have voltage with the key off but with the key on and engine not running have battery voltage. If not then check at the regulator. But before we go any further let me know if this is the alternator set up that you have on the Pontiac.
Brad

---------- FOLLOW-UP ----------

QUESTION: Brad, Thanks for your reply, leave it to me to buy something
"different". The VIN indicates 1962 as does the title, but the
car does have the alternator setup as described by you.
Thanks, Al

ANSWER: Ok, so we don't know who wired it and when. Try what I listed for tests and let me know how you make out to there. Then we will go to the next steps.

---------- FOLLOW-UP ----------

QUESTION: Brad, OK, the Field and relay wires were switched. I'm
getting 14 volts at the battery with the car running. Now my
ammeter is pegged and stays that way. The alternator is
getting hot. This seems like a regulator problem to me so I
changed the regulator. Still over charging. Of course we may
think of a bad battery, hope not, it is new. Could the
alternator be damaged from powering up the relay side?
Thanks, Al

Answer
I agree that it sounds like a voltage regulator problem. Make sure that the voltage regulator is well grounded. I usually run a wire from the regulator to the alternator to make sure that I have a good ground. A bad ground will cause a run a way alternator. It does not sound like the battery or the alternator.