After getting rid of many gremlins in my wiring system by replacing the whole wiring harness, I installed a new Sun Super Tach II. Only 4 wires, Red keyed power, black ground, white instument light and green to the distributor. Works fine untill you turn on the parking or headlights then it goes dead. Double checked my ground and all connections, all are good. When I do pull the headlight switch to park or hedlight positions, I notice there was no backlighting on the tach. :wall:Any ideas?