67 Dat, S/6 car. The fuel and twmp gauges are pegged past the E and C (empty on the fuel and C on the temp? Are they fried or do I have a bad sending unit?

voltage limiter or an open in that circuit.

The gauges are thermal electric by design. They rely on regulated voltage from the voltage regulator (usually located on the cluster board). The regulated voltage should be between 4-7 volts DC. The sending units provide a point of resistance that varies with fuel level or coolant temperature. The resistance value of the sending units (fuel or temp) will cause the respective gauge to move the pointer up onto the gauge (from left to right) to the corresponding reading on the gauge. Without voltage to the gauges, the gauge pointers will normally rest to the left or on the E for fuel and the C for the temperature gauge. Disconnect the temp sending unit wire from the temperature sending unit on the engine (purple or pink wire?). Turn the key to the ON position and measure the voltage at the disconnected connector female terminal end with a DVOM on the 20volt DC scale. Red DVOM lead inside the female connector and black lead to the battery negative terminal. The DVOM should read an average voltage of approximately 6 volts DC. Hope this helps. Let me know what happens. Good Luck. Dutch

Or if you have a test light see if it blinks. It will flash if there is power since it basically turns on and off to get that 5 volts.

Since both are dead, I agree that it is the voltage regulator on the circuit board.

Cleaned off the ground cable engine to firewall. Temp needle moved a little bit. Took the temp connector and grounded it out and the needle moved to mid scale on the gauge. The gas gauge needle didn't move. I need to check that next.

Should have pegged if you grounded it directly.

Mid scale means it got about 3 volts. you can test the gauge seperate by wiring up 2 aa batteris in series and connecting it to the ends.
This too will put it at mid scale.

We can rebuild your gauges for $60 each if they are fried.

Note that DVM's won't read limiter outputs properly because of the way they are changing, it is better to use a test light to check out the limiter.

We also have a solid state limiter to replace the old points one.