Speed Control Systems - Automatic: Testing: Amplifier

CAUTION: DO NOT use a test light to perform amplifier tests because too much current draw will damage electronic components. Use only a voltmeter of 5000 ohm/volt rating or higher.

Make the following tests at the amplifier 6-way connector. Turn ignition "ON" and connect a voltmeter between the Lt. Blue-Black wire and ground.

Depress and hold "ON" switch. Voltmeter should read 12 volts. If not, check control switch or horn relay.
Release "ON" switch. Voltmeter should read approximately 7.8 volts. If not, check amplifier ground connection, fuse, or circuit breaker. Install a known good amplifier and recheck if necessary.
Depress "OFF" switch. Voltage should drop to zero. If not, check switch. Install a known good amplifier and recheck if necessary.
Depress and release "ON" button, then depress and hold "SET-ACCEL". Voltmeter should read 4.5 volts. Rotate steering wheel while watching voltmeter. If voltage varies more than 0.5 volts, check switch.
Depress and hold "COAST" button. Voltmeter should read 1.5 volts. If not, check switches.
Depress "RESUME" (if equipped). Voltmeter should read 6.5 volts. If not, check switch.
If all test readings are correct, perform Servo and Speed Sensor Tests before replacing amplifier assembly.