Bulkhead connector mystery wire

[JG1966]

On my wiring diagram for 72 Satellite/Roadrunner, the "No. 20" spot on the bulkhead connector is empty. I've checked other diagrams and No. 20 is same way. No wire. But I have a blue wire there. Have no idea where it goes or what does. Haven't torn anything apart to trace it, but are the diagrams (from MyMopar) wrong or do I maybe have a non-72 bulkhead in my 72? It had a rallye dash installed and it may explain why I'm having trouble getting my temp gauge to work (maybe other wires are in wrong spot).

 

[vegiguy]

View attachment 390916 On my wiring diagram for 72 Satellite/Roadrunner, the "No. 20" spot on the bulkhead connector is empty. I've checked other diagrams and No. 20 is same way. No wire. But I have a blue wire there. Have no idea where it goes or what does. Haven't torn anything apart to trace it, but are the diagrams (from MyMopar) wrong or do I maybe have a non-72 bulkhead in my 72? It had a rallye dash installed and it may explain why I'm having trouble getting my temp gauge to work (maybe other wires are in wrong spot).

I believe that's for the air conditioner clutch coil but don't quote me on that. That's a 16 or 18 gauge blue wire.

 

[JG1966]

Thanks Vegiguy. That would make sense. Car originally had AC, but it's long gone. I know it was a silly question but it was bothering me.

 

[vegiguy]

You're welcome. Good luck with your car: we need all the luck we can get with the electrical systems Chrysler put in these cars.

 

[JG1966]

Thanks Vegiguy. Can I ask you one question? If I ground my fuel gauge sensor and the needle pegs to full, does that mean my instrument voltage regulator is definitely good? I tried same thing with temp sensor and it didn't budge. The temp sensor is definitely good and all the wires show continuity. Can just gauge itself go bad? It's a Rallye dash that was installed (originally was a standard 120 mph dash). Thanks for any help.

 

[vegiguy]

Usually if your wiring is good, the sending unit is connected properly, and you have a good gauge then the gas gauge should work. Yes, gas gauges go bad, and I've read they can be killed by hooking them up wrong (or the sending unit can). Is this an original sending unit? I replaced my sending unit and gas tank, and when I got the sending unit out it was so crapped up with gas residue it was locked up. You might try taking the sending unit out and seeing if the arm can move freely and if it looks like the float still has buoyancy (probably a good idea to replace the sock on the end of the pick-up tube then, too, if your sending unit seems okay). Check the continuity of the wires going (all the way) to the sending unit itself. You can also check the gauge then by moving the arm up and down to see if it works (might have to ground it first). I don't know what you mean by a dash voltage regulator: I would need to look into that one, but right now I need to leave for an overnight trip I'm taking this weekend so I can't do it now.

 

[JG1966]

Usually if your wiring is good, the sending unit is connected properly, and you have a good gauge then the gas gauge should work. Yes, gas gauges go bad, and I've read they can be killed by hooking them up wrong (or the sending unit can). Is this an original sending unit? I replaced my sending unit and gas tank, and when I got the sending unit out it was so crapped up with gas residue it was locked up. You might try taking the sending unit out and seeing if the arm can move freely and if it looks like the float still has buoyancy (probably a good idea to replace the sock on the end of the pick-up tube then, too, if your sending unit seems okay). Check the continuity of the wires going (all the way) to the sending unit itself. You can also check the gauge then by moving the arm up and down to see if it works (might have to ground it first). I don't know what you mean by a dash voltage regulator: I would need to look into that one, but right now I need to leave for an overnight trip I'm taking this weekend so I can't do it now.

Thanks. Have a nice trip. I wasn't clear in my post. My concern is temperature gauge. My gas gauge problem is almost certainly my sending unit. I'm taking it out soon to check. The Instrument voltage regulator is three prong device on cluster panel that converts 12V to 5V. It controls temp, gas and oil gauges. Trying to determine if I can tell it's good, provided any of the gauges work (my fuel gauge works when I ground the sensor.)

 

[vegiguy]

Yea, Chrysler was the blue ribbon champ at building cars with poorly designed and outdated electrical systems back then and on into the 80's with a few exceptions.

Have you done anything to your gas tank? This gas we have had now for a while is not very kind to the fuel systems of our beloved old Mopars. I have just replaced the gas tanks of most of the old cars I've restored, but I've had people sing the praises to me of the "gas tank restoration kits" you can buy from various sources so that might be an option if you're on a tight budget. I'm a big advocate of doing something to improve the cleanliness of the gas which gets pumped thru the fuel systems of old cars, and I'm NOT a big fan of accomplishing this by adding a bunch of inline fuel filters to the systems which seem to be a popular thing to do. I'm basically a "fix it right the first time" type of person.

Another thing I'm starting to open my mind up to is replacing the mechanical fuel pump on old an car with an electrical pump due to the nature of the gas we have available now since this gas is apparently formulated for modern fuel injected cars which have fuel characteristic requirements almost the exact opposite of what you would want for a carbureted car with a mechanical fuel pump. I don't think I would do this to a show car, but for an old car I was going to drive a lot to fully enjoy it I think I might be tempted to do this to help it start easier and prevent fuel vapor lock.

Sorry to I got a little off track from your original question.