bulkhead Ammeter connectors
Just remember the power to the instruments is not coming from the ammeter. The nominal 12 V into the fuel gage IVR comes from the key switch. It takes a pretty high current to take out the ammeter shunt. Lots of other things will melt first. If the current is real high, it will take out the fusible link. If its 'only' moderately high, it will melt the insulation around various terminals and for those retained in plastic housings (like the bulkhead multi-connector) melt those too. Pictures of
some melted terminals
I can't argue with any of that. There are a host of issues with old terminals carrying high current. Changing the amp gauge to a volt gauge doesn't solve all problems. The wiring in a newer vehicle is mass of small wires for all the electronics in them. Majority of larger wires and high current are out in the engine bay, routed through relays. So their headlight switches, wiper switches, power window switches, every manually operated switch inside can be physically small. Our classics weren't built that way. The newer vehicles are running 80+ amp alternators and have a multitude of fuses. Some of our classics have as little as 5 fuses. Several circuits aren't fused.
As for these Chryslers amp gauges... they are not all the same. Some are pretty well made while others are flimsy. The amp gauge in a rally panel is one of the better ones but... it aint bullet proof. Its needle is mounted on a steel pin about the size of a sewing needle. That pin was pressed into a hole in the shunt. If shunt overheats, the pin falls out. I don't recall how many examples of this is have seen, 3 or 4? That isn't a high number considering how may were produced.
In the bigger picture, the aftermarket doesn't want us to do MAD bypass or any other mods to our 50+ year old wiring. They want us to purchase all new everything from them.
My 67 wiring wasn't in poor condition but the service disconnect at the fusible link did show corrosion and melting, and that was with the original regulator and 36 to 42 amp alternator. Bulkhead connector and amp gauge terminals still looked fine. I too choose to make a few changes including headlight relays, MAD bypass, and amp gauge delete, in effort to prevent some of the possible issues down the road and the need/cost of new wiring harnesses.
A chain breaks at its weakest link. This owner sees his weak link at bulkhead terminals. To address that moves point of failure to next weakest link. I found my weak link at fusible link connector but didn't stop there. Good luck to all.
