"ON" Circuit Test
- Turn ignition on and connect voltmeter to Lt. Blue-Black wire and ground. Depress and hold "ON" switch in steering wheel. Meter should read 12 volts. If voltage is not available, check horn relay circuit and perform CONTROL SWITCH TEST .
- Release the "ON" switch. Voltmeter should now read approximately 7.8 volts on Ford, Mercury, Fairmont, Zephyr, Mustang and Capri, 12 volts on all other models. If voltage is incorrect, check for good ground on amplifier, blown fuse and/or circuit breaker. Install a known good amplifier and recheck "ON" circuit if necessary.