Speed Control Is Inoperative

1. Apply brake pedal and check if brake lights work. If brake lights work, proceed to step 2. If brake lights do not work, check stop lamp circuit and stop lamps.
2. Check for proper operation of actuator lever and throttle linkage. If satisfactory, proceed to step 3. If not satisfactory, adjust or service as necessary.
3. Ensure that all system vacuum hoses are tightly connected and are free of cuts, cracks and kinks.
4. Disconnect hose between check valve and servo, at servo end. Apply 18 inches of vacuum to open end of hose. If vacuum can be pumped and held, proceed to step 5. If vacuum cannot be pumped or held, replace check valve.
5. Check vacuum dump valve. If valve operation is satisfactory, proceed to step 6. If valve operation is not satisfactory, adjust or replace as necessary.
6. Disconnect reservoir vacuum line at check valve. Apply 18 inches of vacuum to open end of hose. If vacuum can be pumped and held, proceed to step 8. If vacuum cannot be pumped and held, proceed to step 7.
7. Disconnect reservoir vacuum line from reservoir port and plug open end, then supply 18 inches of vacuum to other end of line disconnected from the servo check valve. If vacuum can be pumped and held, replace reservoir and repeat step 6. If vacuum cannot be pumped and held, replace reservoir vacuum hose.
8. Perform tests on control switches and circuits. If control switches and circuits are satisfactory, proceed to step 9. If control switches or circuits are not satisfactory, repair or replace as necessary.
9. Perform tests on servo. If servo operation is satisfactory, proceed to step 10. If servo operation is not satisfactory, replace servo.
10. Perform tests on speed sensor. If sensor operation is satisfactory, proceed to step 11. If sensor operation is not satisfactory, replace sensor.
11. Replace amplifier with known good amplifier. If system operation is satisfactory, replace amplifier. If system operation is still not satisfactory, ensure all system electrical connectors have proper contact.