What do I need and what do I don’t!

[RustyRatRod]

Love to find an example where an ammeter in a '75 actually caused a fire.
I had a '75 4 door Valiant and it did not catch fire. Not even once.
Headlights tripping circuit breaker, yes, and that was pretty much the only electrical problem with it.

If the OP's car has the seatbelt interlock, then there are simpler ways to permanently bypass it.

Or he could just wear the seat belt.

 

[triumphman]

Use these copies for color codes and locations at the firewall connector. They are from a 75 Swinger's factory manual.
If you can locate wiring harnesses out of 73 to 76 "A" bodies . Be sure to check cracks and splices and clean every connector.
Splice with SAME colors.
Good luck

 

[72RoadRunnerGTX]

Consider adding a field relay, mentioned towards the end of this video.

 

[67Dart273]

Consider adding a field relay, mentioned towards the end of this video.

THIS GUY HAS READ MY POSTS!!!! ****!!! HE STOLE MY POSTS!!! Well explained!!


HOWEVER THIS IS NOT HOW I recommend wiring that relay. Instead of ONLY feeding the VR, relieve the ignition switch "run" (IGN1) of ALL load by cutting the dark blue, and feeding ALL the underhood loads, including the ignition circuit, off that relay.

 

[72RoadRunnerGTX]

THIS GUY HAS READ MY POSTS!!!! ****!!! HE STOLE MY POSTS!!! Well explained!!


HOWEVER THIS IS NOT HOW I recommend wiring that relay. Instead of ONLY feeding the VR, relieve the ignition switch "run" (IGN1) of ALL load by cutting the dark blue, and feeding ALL the underhood loads, including the ignition circuit, off that relay.

Thanks, I’ve been dealing with these types of voltage drop issues dating back many years, to my time at the dealers in the seventies, well before the internet and any of these current automotive forums. Can’t take credit for the “flied relay”, that is a factory idea starting in the mid to late seventies B & C bodies with optional high output alternators drawing a fairly high level of field current.

Not a fan of running the ignition power supply (ignition1) through a relay for the same reason the factory didn’t use it's own circuit protection on that circuit. While relay reliability has improved, the relay and its related terminals and connections are just more points of possible failure. Agree, the ignition switch itself is a common point of high internal voltage drop. Running the ignition switch leads through Molex connectors starting in ’70 didn’t help with that.

 

[67Dart273]

^^Actually the older dash mount ignition switches are also a problem, maybe because they are older now.^^

I am 76. First got into problems, myself and friends, with Mopars, in the early 70's, while stationed at NAS Miramar, San Diego. I was an electronics tech. Maintained GCA RADAR and TACAN

 

[Clelan]

For a guy on a budget, buy a factory service manual, a good electrical crimping plier, miscellaneous packard 56 connetors and study how each circuit works. Take the harness out from under the hood and go wire by wire. Remove what isn't needed, repair what is needed, then once it's tested and verified, resheath each individual wire bundle so it matches original routing. It's not hard, and the few times I have done this, I was surprised how good of shape the actual wire was in most areas. I did this to the entire wiring harness in my car during the resto.

The problems come in at the bulkhead connectors on the firewall and places that see lots of movement.

Cley