The Ford Barn - View Single Post - Alternator Voltage Regulator Burning Out?

John Borland · 09-01-2018, 12:53 PM

Hello All,
I have a 1931 Model A Coupe that I converter to 12 volts twelve years ago. Until recently I have had no problems with the electrical. However the car has started to burn through coils. An epoxy filled Pertronix 3 ohm coil will now only last about 500 miles. The coil gets hot to the touch after just a few miles of running (oil filled coils are even worst). I have been unable to find any electrical shorts with my multi-meter, but did find (with a multi-meter) that the alternator output jumps around so much that it is impossible to read on the meter (this made me think that the internal voltage regulator was bad). I was hopeful that the erratic alternator voltage to the coil was my problem.

I took the alternator to Advanced Auto for testing, and they confirmed that it was shot. I purchased a rebuilt 7127 SE, 12v, single wire, negative ground alternator. I installed the alternator and immediately tested its output. For a few seconds it showed an output of 15 to 17 volts, but then it went to bouncing around so much that a reading could not be had. I took the alternator back to Advanced Auto; it tested bad, and they gave me another one. They tested this alternator before I left the store and it tested good. Took home, installed, and experience exactly the same erratic readings.

Not sure what to do at this point. Please respond if you have any experience or suggestions that may help in troubleshooting the coil, and now alternator problem. I have pretty well exhausted my limited knowledge. As a point of fact, this problem may of been going on for some time without my knowledge, since I have only recently been taking the car out on long tours where it is run for extended times. Thanks in advance for any help you may be able to provide.

-John

09-01-2018, 12:53 PM	#1
John Borland Junior Member Join Date: Aug 2015 Location: Spring Creek, Nevada Posts: 13	Alternator Voltage Regulator Burning Out? Hello All, I have a 1931 Model A Coupe that I converter to 12 volts twelve years ago. Until recently I have had no problems with the electrical. However the car has started to burn through coils. An epoxy filled Pertronix 3 ohm coil will now only last about 500 miles. The coil gets hot to the touch after just a few miles of running (oil filled coils are even worst). I have been unable to find any electrical shorts with my multi-meter, but did find (with a multi-meter) that the alternator output jumps around so much that it is impossible to read on the meter (this made me think that the internal voltage regulator was bad). I was hopeful that the erratic alternator voltage to the coil was my problem. I took the alternator to Advanced Auto for testing, and they confirmed that it was shot. I purchased a rebuilt 7127 SE, 12v, single wire, negative ground alternator. I installed the alternator and immediately tested its output. For a few seconds it showed an output of 15 to 17 volts, but then it went to bouncing around so much that a reading could not be had. I took the alternator back to Advanced Auto; it tested bad, and they gave me another one. They tested this alternator before I left the store and it tested good. Took home, installed, and experience exactly the same erratic readings. Not sure what to do at this point. Please respond if you have any experience or suggestions that may help in troubleshooting the coil, and now alternator problem. I have pretty well exhausted my limited knowledge. As a point of fact, this problem may of been going on for some time without my knowledge, since I have only recently been taking the car out on long tours where it is run for extended times. Thanks in advance for any help you may be able to provide. -John