Trying to troubleshoot why my amp gauge has no movement.Volt reading on either post on the back of gauge is 12.2 vdc with the key off,and about 13.7 with the engine running.Car charges fine,just no movement ever on gauge.Do I have a bad gauge or am I troubleshooting this wrong?

Amp gauge is really a milivolt meter and reads the difference between the voltage at the horn relay and junction block. The amp gauge is wired to 2 places that always have power, see pic. You may have one or several problems. One of the "ends" of the amp gauge leads may be open or a fusible link is blown, one of the copper traces on the PCB board is burnt, or if all the wiring is not factory.
http://www.chevelles.com/showroom/data/500/Chevy_old_with_amp_gauge.jpg

So I could possibly have an open wire on one of the wires to the gauge?Thanks for the diagram.

Don't want to be the bearer of bad news but more than likely one of the traces on the circuit board is burnt. I have restored many 70-72 gauge sets and it is common for this to happen. The trace is acting as a fuse. The trace cannot handle nearly the current the wires with fuseable links can handle. A temporary short at the horn relay terminal will take out the trace in a second without blowing the fuseable link. But as stated above I would check these wires first.

What is the best way to bench test the amp guage?

WELL, I CAN TELL YOU WHAT NOT TO DO! Do Not try to put a load in series with the amp guage to see if it will move. My Guage was not moving iether so I pulled the wire off the horn relay and placed a light in series wirh the circuit. By the time I got back to look at the guage to see if it moved I had burnt my circuit ribbon for the cluster! I guess Im pulling the hole thing apart again!
Phil

if it is a burnt trace on the pcb, it's very easy to to hard wire the amp gauge directy to the pcb plug with a couple of short wires and ring terminals.

What is the best way to bench test the amp guage?
A "AA" battery. Only have it connected for a very short period of time.

Disconnect one wire to the gauge then measure the voltage at both wires again. If you have an open circuit somewhere only one wire will still read 12v.

It was the ribbon circuit that burnt but the guage is also bad. I am doing to have the guage switch over to a volt meter before reinstalling it!
Phil
70 El Camino