1972 Plymouth RR --> HEATER NOT WORKING

[72RoadRunnerGTX]

That is the alpha-numeric conductor identification, in this case G420DBL- (G4) is the circuit identifier, (20)-20 ga. wire size, and (DBL)-dark blue in color. Posted above is the first page from FSM showing the requested cluster color codes. The diagram is indicating the cross-over of that circuit to the second page of the rallye dash harness wiring diagram.

[zextrot]

Ok, I have traced the line we are talking about (fuel gauge) to the second page of the diagram. It terminates into a little box labeled "1". Is this a fuse, resistor or relay?? Then how do i continued tracing the same wire? The fuel gauge has to go to the sending unit, so i'm trying to trace it all the way.

The temp gauge goes to the temp sending unit on the motor. Looks like someone has removed that because i dont see a temp sending unit at all, so i need to find the right wire to run to a new sending unit.

The battery gauge doesnt work either, so i assume it's not hooked up.

If you would be so kind as to help me figure out how to read the fuel gauge line, i should be able to figure out the others once i know how to read it.

[72RoadRunnerGTX]

That’s the six-way disconnect to the rear body harness, located behind the driver’s side lower kick panel. The circuit continues back to the fuel tank sending unit through a grommet/hole in the trunk floor.

[zextrot]

Ok, then what is this? It's where the temp and oil gauges terminate.

[72RoadRunnerGTX]

Bulkhead connector, engine wiring harness;

[JimT1971RR]

I suggest that you inventest in a set of service manuals, especially since your are doing wiring work.

Here is a recent re-print I just found on E-bay:

http://www.ebay.com/itm/1971-Plymouth-S ... re&vxp=mtr

You might also be able to find it on a cd, but I find the book the better way to go.
I have an original set and it really helps.

[zextrot]

I found this wire sort of "rigged" up and it has melted spots. I wonder what this big wire is ... ??

[72RoadRunnerGTX]

Holly Smoke Batman! Those are the ammeter leads, someone has “by-passed” the ammeter without insulating the connections. Serious fire hazard and likely explains the heat damage seen. Recommend inspecting the remainder of the charging circuit, the bulkhead connectors and both the red & black wires in the engine compartment leading to the starter relay and alternator. Repair or replace as necessary.

[zextrot]

That jives with what we were thinking - that someone bypassed the ammeter. Why would they do that and how can i put it back the way it's supposed to be?

[gcoupe72]

Wires through the bulkhead for the ammeter are a common trouble spot on many Mopars with original wiring.
Resisitance =heat, melted wires, smoke and flames, etc. The meter probably failed, and the only way to drive the car is to bypass it. Many run a new wire that bypasses the bulkhead connector (use a grommet!).
If 100% original is not important, eliminate the ammeter, and use a voltmeter, much safer!
Don't give up, you'll get there!

[zextrot]

I think i'm getting there with all your help - i've replaced a bad starter relay, replaced temp sending unit, oil pressure sender and fuel sender. If i replace the ammeter with a voltmeter, i would have to rip out the ammeter and have a new meter in there that doesn't look like the others. i guess i could mount it under the dash instead ...