1966 Ford Mustang Convertible Other - Electrical & Lighting Systems

Question: 289 Engine. I have a problem with the battery getting charged. I have replaced the battery, alternator and the voltage regulator. If the battery is charged the engine will start and the car will run fine for as long as I want to drive it. After starting the engine 4 or 5 times the battery goes completely dead. I had the new battery tested and it came out just fine. The battery doesn't drain over time it just drains when the car is started alot because its not getting recharged. What could this possibly be? Could it have anything to do with the Relay for the starter? Thanks for your help!

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Technican: You need to use a voltmeter and see if the alternator is charging at all. If you don't have a voltmeter, turn on the headlights and start the car. Do the headlights get brighter? If no, it time to check the wiring. Make sure the body ground is good and check the wiring at the alternator (make sure you have power from alt. to battery positive) and voltage regular. Let me know what you find. Also, many chain autoparts stores will check the charging system with a tester free of charge.

Owner: Thank you for the reply. The alternator has been checked as well and there where no problems with it. So you think I should start with the Body ground? How would I check that with a voltage meter? Thanks for your help.

Technican: I will see if I can find a wiring diagram for you to troubleshoot from.

Owner: I put a voltage meter on the car this morning and this is my findings... With the car turned off I measured the voltage at the battery and got a reading of 12.8 volts. I measured the voltage on the wiring harness for the voltage regulator and got the same reading of 12.8 volts. This was the main wire coming from the alternator. I also measured the amps being drawn from the battery with the key off and got a reading of 0 so I don't believe anything is drawning amps and draining the battery. With the car started. I measured the voltage at the battery and got a reading of 12.5 volts. I measured the output from the alternator (the red lead coming out) and got a reading of 21.3 volts. Could this possibly lead me to believe that the voltage regulator is bad? Its brand new but I also know that they can go bad very easy. What do you think of these new findings? Is there a way I can test the voltage regulator to see if its bad or not?

Technican: It seems the voltage regulator is 'turning the alternator on'. Where does the red wire go? Follow the red wire and determine why 'charging' voltage is not reaching the battery. The red wire is the larger hot wire, correct? It should go to the battery or starter/relay. Let me know what you find and we'll go from there.

Owner: The red wire from the Alternator goes to the Voltage Regulator. From there, the wires coming from the Voltage Regulator go back to what I believe is the starter relay. The wires from the voltage regulator and the battery are both connected on the same side of the starter relay. I put my voltage meter up to that wire going into the starter relay, coming from the voltage regulator, and I get the same reading as the battery (12.5) when the car is running.

Technican: Yes I think they do connect to the voltage regulator. So far I haven't been able to locate test procedures for the voltage regulator itself. It is entirely possible you got a bad regulator. Call the parts stores and see if they can test the regulator off your car. Here is a wiring diagram for the circuit- copy and paste into your address bar- autozone.com/images/cds/gif/large/0900823d801c3e69.gif

Owner: I changed out the voltage regulator and it didn't fix the problem. I think you may have been on the right track with problems with the wiring. I think I have changed out everything else that could be problematic.

Technican: Did the link I gave match your charging system?

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