64 Dart gas gauge wire missing?

[robjkc]

I'm looking at fixing the gas gauge on my 64 Dart. It currently doesn't register anything.

I looked behind the dash and noticed that there was a black wire secured by a nut to one of the terminals but the other terminal didn't have a connector going to it and was missing the securing nut. Here's a picture of the back of a 64 instrument cluster for reference.

I found a lose red wire but it wasn't the type that could be secured by a nut (sorry for my non-technical terminology). I thought I would just stick it on the end of the terminal to see what happened and the gas gauge went all the way to full when the car wasn't running. I would have to get a different connector for the red wire to secure it under a nut on the terminal, but I'm not even sure if this is the correct wire since it was a different type of connector.

I'm not really sure what is going on so I thought I would ask and see if anyone had any ideas.

Also, I noticed I was missing a bulb socket to my oil light. I stole the bright light indicator socket and tried it in the oil light but the oil light does not come on. I'm thinking I'll need to replace the oil pressure indicator switch on the engine.

Thanks for the help!!

 

[RonnyB]

Hi Rob, I think your gauge situation can be figured out.

The gas temp gauge require less than 12v to work. The voltage is lowered by a mechanical voltage limiter. In the Dart, it's built into the gas gauge - that's why it has three connections instead of two.

I've attached a picture of a spare instrument cluster. It's missing the temp gauge and light sockets, but it gives a closer view of what you're dealing with.

The three connections on the gas gauge are labeled on the circuit board as I, A and S.
The 'I' connection is on the left and provides 12v to the internal limiter through the wire socket below. That black wire should go to a metal can that's screwed onto the metal frame of the instrument cluster (see my pic). The can is a condenser/capacitor that filters the 12v.
The 'A' connector is the output of the voltage limiter that also powers the temp gauge. It's the upper connector that has the brass clamp over it.
The third connector is the one labeled 'S' and it goes through the wiring socket below to the sending unit in the gas tank. It should not have any wires connected to it. I'm not sure what's up with the loose red wire, but it doesn't go to the gas gauge.

Whether the limiter is external or built into the gas gauge, they are notorious for going bad. When they do, both the gas and temp gauges will not work. It's important to know if the problem is with the limiter or something else. The big question is, does your temp gauge work now? If it does, consider yourself lucky!

The next likely suspect is a bad sending unit in the gas tank or a loose/broken connection between it and the gauge.
Check the gauge, by taking the wire off of the sending unit on the gas tank and connect it to a good ground somewhere on the body. The gauge should go read full. If it does, the sending unit is bad or isn't grounded.

All this should get you going on figuring out what's wrong. If you have problems, just let us know.

 

[green1]

Correct, instead of just trying loose wires; find the one from the tank. Don't think it is red, as usually red under the dash is a 12v hot.

 

[RonnyB]

Correct, instead of just trying loose wires; find the one from the tank.

If the wiring is intact, you don't need to look for the wire from the tank. It goes through the socket connector. (In the picture I posted, it's the upper left pin that goes to the gauge terminal labeled 'S')
If you have a meter that measures resistance, try measuring from ground to the place on the socket that that pin connects to. If the wiring and sending unit are good, it should measure less than 100 ohms. Around 10 ohms if the gas tank is full.

Again, if you have any questions or problems, let us know. We want you to get that gauge working again and detailed troubleshooting procedures add to the value of this forum. So it's all good...don't be afraid to ask questions!8)

 

[robjkc]

Thanks for all the helpful advice! My temp gauge is working so maybe the gas gauge is still good. I'll see what I can figure out this week and post my results.

I'm looking into RTE limiter that is mentioned in the other thread, which may be an option down the road.