I have a 66' with 428 engine. All guages seem to work with exception of Temp. guage which stays on far left "Cold" end. Any known methods of checking this guage prior to me pulling and replacing temp. sensor on intake manifold? Also note periodically from time to time all guages do not work, could this be a flaky constant voltage unit assy. issue?
Thanks Greg

A quick test of the sender unit is to remove the wire and temporarily ground it. Turn the ignition switch to "on". If the guage now registers, the sender is defective. The guage itself can be tested by applying 3 or 4 volts to the guage terminals. If the guage registers now, the power supply or "guage voltage regulator" is faulty. Check the wires for chafing or other damage as well.

Thanks Kandiapple66 for the tip on testing temp guage. I grounded the lead wire to sensor and turned on ign switch. The guage did respond and move to right. I just ordered a replacement sender. Thanks Again. Greg

Check for a good ground at the constant voltage unit. That could cause the gauges not to work from time to time.