I am installing some standard gauges back into my 65 couple. I have tried both with the old voltage regulator as well as a new one. I followed the wire diagrams for the 65 mustang so my wires should be right. I tested it with just the fuel and temp gauge hooked up and it seems to work just fine. BUT, when I attach everything back, particularly the little instrument bulbs, the fuel and temp gauge shoot all the way to max, and stay there. When I take off the lights again, the gauges seem to work normal. This happens with both new and old regulators. What gives?

 

You have adraw somewhere. Since it only happens when you plug in your cluster lights I would focus on that portion of the harness. Is the harness in good shape or has it been hacked up?

Also, just for fun, verify that you have a good ground.