Servo Test
- With ignition switch in "OFF" position, disconnect servo wire harness connector. Remove vacuum hose from brake pedal vent valve nipple on servo. Disconnect servo cable from throttle linkage at carburetor.
- Connect an ohmmeter between ground and Red. Ground and Orange. And Ground and White wire terminals of servo wire harness connector. See Fig 1 . Observe ohmmeter during each test. An infinite (open circuit) resistance should be indicated for each wire terminal.
- If ohmmeter indicates less than infinite resistance on any terminal, servo has short circuit to ground and must be replaced. Short circuit will also cause damage to control module and it must be replaced.NOTE: Without sufficient load, solid state circuitry in control module will be damaged by excessive current flow.
- If servo does not have any short circuits to ground, connect a vacuum gauge to brake pedal vent valve nipple. Connect a jumper wire from chassis ground to Orange wire terminal of servo wire harness connector.
- Connect a second jumper wire to battery positive terminal and start engine. Momentarily connect jumper wire and simultaneously touch Red and White wire terminals in servo wire harness connector.
- Vacuum should be indicated on gauge while jumper wire is in contact with wire terminals. Perform this test several times to make sure that solenoid valves are working properly.
- With no voltage applied, solenoid charge valve is closed and solenoid vent valve is open. With 12 volts applied, solenoid charge valve is open and vent valve is closed.
- Turn engine off and remove jumper wires. If servo is defective, replace it. If okay, connect vacuum hose, wire harness connector and throttle linkage to servo.