Electrical Issue

[Charles Moore]

I'm needing some help. I have an over charging issue with my 70 Challenger 440. Brand new wiring harness, new voltage reg., and the alternator checks good. I have plenty of ground connections. It is fine at idle but, when it warms up and I give it some gas above 2000 rpm for a length of time, the amp gauge pecks and the lights brighten up. Shut it off and let it cool for a while, 10/15 minutes, start it up and it seems fine until it gets some throttle. it idled for about 10 minutes and seemed fine, pulled it out of the shop, turned onto the street, grabbed second gear, and bam, needle pegged again. I'm at a loss. Could it be the alternator maybe overcharging so much it by passes the regulator? HELP!!!

 

[Adam]

Do you have a spare voltage regulator you can swap in? I would try that first, and they are not very expensive. Since it happens after it warms up, and not immediately, I would suspect the alternator is fine, as you say. But you should still check alt output voltage after it warms up. I would use a voltage meter on the output stud of the alt, testing it at idle & at revs, when warm/hot.

Lastly, ditch the ammeter it can be a fire hazard with all those amps running thru it. An easy upgrade is to run a big wire (with fusible link) from the output stud of the alternator to the positive battery terminal. This will reduce the amps going thru the bulkhead connector and ammeter. The ammeter will not be very accurate after this mod and an upgrade to a voltmeter would be helpful.

You may know all of this already, but for others that read this; here are some great tech links you can bookmark into your browser:

Vintage Chrysler electrical repairs and updates

Vintage Chrysler electrical repairs and updates (part 2)

Mopar Action pages at Allpar

 

[Chryco Psycho]

Make sure the VR is properly grounded

 

[fasjac]

Adam and Chryco right on. I’ve run into this many years ago. At that time the simple fix was using the oe regulator after using aftermarket. And if you still have the ballast resistor, go ahead and replace it as well. Cheap

 

[Charles Moore]

Do you have a spare voltage regulator you can swap in? I would try that first, and they are not very expensive. Since it happens after it warms up, and not immediately, I would suspect the alternator is fine, as you say. But you should still check alt output voltage after it warms up. I would use a voltage meter on the output stud of the alt, testing it at idle & at revs, when warm/hot.

Lastly, ditch the ammeter it can be a fire hazard with all those amps running thru it. An easy upgrade is to run a big wire (with fusible link) from the output stud of the alternator to the positive battery terminal. This will reduce the amps going thru the bulkhead connector and ammeter. The ammeter will not be very accurate after this mod and an upgrade to a voltmeter would be helpful.

You may know all of this already, but for others that read this; here are some great tech links you can bookmark into your browser:

Vintage Chrysler electrical repairs and updates

Vintage Chrysler electrical repairs and updates (part 2)

Mopar Action pages at Allpar

Thank you. Yes I have changed VR which doesn't seem to cure the problem. I have attached new ground wires from the negative side of the battery to the body and from the engine block to the firewall. What gauge wire to you recommend with a fusible link? Also, can the ammeter in my stock cluster be upgraded to a voltmeter? After the complete new wiring harness was installed ( front to rear ) I have driven this car from Abilene TX to DFW, down to Ennis TX to the drag strip, and several car shows within a 100 mile radius the last couple of summers. Driving to the DFW area last Sept is when it happened about 60 miles into the trip and lights became bright, tach started jumping, ammeter was pecked, and the fuel, oil, temp gauge stopped working.

 

[Charles Moore]

Adam and Chryco right on. I’ve run into this many years ago. At that time the simple fix was using the oe regulator after using aftermarket. And if you still have the ballast resistor, go ahead and replace it as well. Cheap

Thank you. No ballast resistor. Running a Pertronix unit.

 

[Charles Moore]

Make sure the VR is properly grounded

Thank you. It is. I removed the VR, removed any paint, and replaced the studs/bolts.

 

[Adam]

Depends on your alt amp output. 6 ga for 55 amps, 2 ga for 95 amps.... yes on the voltmeter gauge swap, I have one in my 71 Challenger rally dash. Red line Gauge Works did mine. Nice work, but slow....

Wire Gauge Sizes and the American Wire Gauge (AWG) | Learning Center | Sonic Electronix

 

[340SHAKER]

Charles, did you ever figure the problem out? My 71 340 with all new wire harnesses is doing the exact same thing.

 

[Charles Moore]

Charles, did you ever figure the problem out? My 71 340 with all new wire harnesses is doing the exact same thing.

Yes, it was my alternator. It bench tested good however, they shop couldn't but it under that much of a load. Something inside was disconnecting when it got warm and had a real high load above 2000 rpm. I bought a new one from Auto Zone just to give it a try and, it has worked great every since. Volts are good while running. I have driven about 600 miles with no problems.

 

[340SHAKER]

Thanks for your reply. This thing \has been driving me crazy. I have made all the suggested changes with no luck. I plan to replace my alternator as well. Thanks again, Merry Christmas!

 

[Charles Moore]

Thanks for your reply. This thing \has been driving me crazy. I have made all the suggested changes with no luck. I plan to replace my alternator as well. Thanks again, Merry Christmas!

Roger that. I was going crazy chasing it down. Added 2 extra grounds from the motor to the body, new VR, ect. It really became frustrating when I had the alternator checked at 2 different places and it benched tested good. I hope you get it squared away. Merry Christmas to you as well.