Temp & fuel gauges - what am I overlooking?
The engine is grounded at the firewall, and the battery is grounded to the engine of course and also has a ground to the rad support.
The cluster is grounded to the dash frame. The gauge lights, radio, etc are grounded to the same place. They all work.
OK ,Try this. You will need a helper.
1. Disconnect wire from gas tank sending unit. ( Its blue in a 68 Cuda)
2. Have someone turn key to acc position.
3. Put an alligator clip or test lead into the end of the blue wire from the tank and momentarily ground it out to the chassis. Have your assistant monitor if the gauge pointer is moving to full position. Do not leave grounded for very long or you will burn out the fuel gauge.
If the gauge moves, the issue is in the tank sending unit.
4. No movement ? go to the rear wiring harness connector that should be in the driver side footwell. It has the rear taillights, id light , and dome light wiring in it.
Disconnect it.
Find the blue wire in the part of the connector the goes to the rear of the car.
Keep the tank end of the blue wire grounded to the chassis.
Now Using the meter, Put one lead in the end of the blue wire at the footwell connector and ground the other lead to the car chassis. The meter should beep indicating continuity and verifying that the wire from the footwell connector to the gas tank is good. If not, the wire is cut or the connector pins are bad or not making contact.
Let me know how this goes before we go through the next process.
Cheers!