QuestionQUESTION: I have a 1970 buick lesabre. I replaced the alternator, voltage regulator and battery, but the generator light comes on. The vehicle has been sitting for a lengthy period of time.
ANSWER: The first thing that we need to know is if the alternator is charging or if the problem is in the light circuit. I would like you to connect a voltmeter across the battery with the engine running and all the accessories off. The voltage should be somewhere between 13.6 volts and 14.2 volts. If the voltage is lower then the alternator is not producing any electricity. If the voltage is higher then the problem is in the light circuit. If you would get the voltages and let me know, then we can start on the right path to get your problem resolved.
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QUESTION: The voltage I am getting is 12.31 volts. Thanks Guy
ANSWER: Ok, you are truly not charging. Now, are the parts that you replaced new or used from a swap meet? Now, there is a big wire on the back of the alternator and a push in connector. Remove the plug in connector. Stamped on the alternator where that connector is should be an "F" near on and "R" near the other. make up a jumper wire so that you can connect the big wire with the "F" terminal. Now with your voltmeter connected from the larger terminal at the alternator to ground start the engine. The voltmeter should be registering 13.8 or better volts. If it is registering near the 12.3 volts then the alternator is bad. If If there is no voltage at the back of the alternator when the engine is not running then there is a break in the wiring between the battery and the alternator. If the voltage is up then I would suspect the voltage regulator. Keep me posted.
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QUESTION: When I put a jumper from the f terminal to the large wire in back of the altnernator it keeps sparking and then melted my jumper.
AnswerOn any alternator the field terminal should draw no more current than a tail light bulb. So, if it drew enough to melt your jumper wire it tells me that there is a short inside the alternator, either the rotor or a shorted brush holder. Now when we rebuild those alternator we use a short pedicel of wire like a heavy paper clip to hold the brushed in place while assembling the alternator. Then the pedicel of wire should be sticking out of the back of the alternator. Before we install the alternator we remove the wire and the brushes are supposed to seat on the rotor ring. I wonder if some one forgot to remove the wire. Well at any rate the alternator needs to come off for service and sadly to say the voltage regulator has probably been damaged. Keep me posted.
