1970 Challenger overcharging issue

[i_taz]

I just noticed this but guessing it's been thr...

 

[brown_devil]

For various reasons I have only recently been able to work on my car. Here's is what I found. The insulation on the black wire on the passenger side of the bulkhead connector had melted in one spot and had also melted thru the wire that supplies the passenger side marker light causing both of them to be in contact. I am thinking that the extra load on the wire from the light caused the ammeter to not read correctly? About 4" of the black wire looked like it had gotten hot so I cut off about 8" of the black wire and soldered on a new piece along with a new connector. I also replace the voltage regulator once again. I used the car a few times since and did not have any issues until today. I went for a ride that included about 30 minutes of highway use and again the ammeter went all the way to the right. When I slowed down, everything went back to normal. When I got home, I looked at the wires, the black wire again had a melted spot with bare wire exposed for about 1/4 inch about 3-4" from the connector. It almost looks like the insulation rubbed something but it is definately melted so it was hot. There is no sign of melting at the connector or at any other place within a foot of the connector. I have a new dash harness on order but I want to figure out why I am melting the black wire since I don't want to ruin a new harness. The engine compartment side of the black wire and connector look fine as well as both sides of the red wire out to the starter relay. Seems like there is some kind of high resistance that is causing the wire to heat up but I don't know where to look.

 

[taxspeaker]

A voltmeter is as useless as an idiot light for monitoring real time charging system health, much more valuable information available from ammeters if you know what you are looking at. Ammeters with properly maintained connections and insulators are not known for spontaneously “shorting out”, that’s just BS, a myth.

We were dealing with failed bulkhead connections at the dealers back in the seventies, it’s a well-documented weakness in the original design. But then these cars were never built to last more than a few years, until the next trade-in. I read a lot of advice here about replacing full harnesses with new reproductions to address these kinds of issues, “just to be sure”. Problem with that is, they are just expensive reproductions of the original design including the Packard terminals in the bulkhead charging circuit. Guess what, that doesn’t fix anything, they burn up after a short while too just like the originals. Dielectric grease on the terminals is not going to allow corroded or heat damaged Packard terminal handle any more current, not a permanent fix by any means.

Nobody said anything about connecting high current add-on loads to the factory dash harness or fuse block. All factory loads at splice 1 can be feed from the original 12 ga black ammeter lead. Larger gauge runs out to the alternator can have added loads taken off that run. Keeps all load on the alternator side of the ammeter.

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View attachment 85178

Excellent guide, thanks!
Question-can the firewall circuit breaker handle multiple outputs? I am running electric fuel pump, electric fan and auxiliary fog lights on battery side and constantly show overcharging on ammeter, even if just running fuel pump. All grounds are good, voltage reg good and checked, alternator good and checked, but this reading bothers me. This is on the Black Ice Superbird I am driving to Arctic Ocean in July and I don't want to run any risks on electrical.

It also looks like the red wire to starter relay/fusible link is a direct wire now instead of through the bulkhead?
To summarize, I think:
1. Red wire on amp gauge is "new" direct to starter relay/fusible link and leaves that portion of original wiring harness unused?
2. Original black ammeter lead is still in use?
3. Added red feed for blower motor relay (I don't thinks I need to do that?)
4. Added "new" black feed direct through bulkhead to "new" firewall circuit breaker
5. Then, added auxiliary power source via new firewall circuit breaker, each auxiliary run through it's own separate circuit breaker.

Thanks and sorry for being a pain
Bob J

 

[72RoadRunnerGTX]

Excellent guide, thanks!
Question-can the firewall circuit breaker handle multiple outputs? I am running electric fuel pump, electric fan and auxiliary fog lights on battery side and constantly show overcharging on ammeter, even if just running fuel pump. All grounds are good, voltage reg good and checked, alternator good and checked, but this reading bothers me. This is on the Black Ice Superbird I am driving to Arctic Ocean in July and I don't want to run any risks on electrical.

It also looks like the red wire to starter relay/fusible link is a direct wire now instead of through the bulkhead?
To summarize, I think:
1. Red wire on amp gauge is "new" direct to starter relay/fusible link and leaves that portion of original wiring harness unused?
2. Original black ammeter lead is still in use?
3. Added red feed for blower motor relay (I don't thinks I need to do that?)
4. Added "new" black feed direct through bulkhead to "new" firewall circuit breaker
5. Then, added auxiliary power source via new firewall circuit breaker, each auxiliary run through it's own separate circuit breaker.

Thanks and sorry for being a pain
Bob J

Have a look here, see if this answers any of your questions.

 

[taxspeaker]

Have a look here, see if this answers any of your questions.

Fantastic, thanks, I think it answers everything!
Bob J