The gauges on my 66 coupe are not wirking, the havn't since I have had the car.The speedo works but is out by about 10mph at 60mph. The Fuel, Temp and oil gauges needle just moves to the far right of the gauge when i start the car and the amp gauge does nothing. I have replaced the sending units and the engine wiring harness. I've had the gauges checked and am told they are ok.

 

How about the voltage regulator for the gauges?

 

And check the body-to-battery ground wire.

 

The voltage regulator was replaced when the gauges were checked. The body earth wire seems fine.
thanks

 

The gauge circuit doesn't look to be fused, so your'e either missing the power, the ground, or the gauge is bad. The gauge Vreg (5vdc) is powered directly from the ignition switch and feeds all 3 gauges thru wire 30 ( blk green stripe). Recheck the voltage output for 5 V. Also, check to make sure that the Vreg ground is clean and the instr cluster ground wire is hooked up and connected to a clean ground behind the instr panel. The ammeter usualy doesn't do much more than wiggle around center, pull your headlights on and look for a small deflection to the left. Otherwise look into having your alt checked (autozone will do it for free).
You may have the wrong gear in your tranny for the speed issue, there's been other postings in the last couple of months on how to choose the right color gear.