Speed Control Is Inoperative

1. Inspect all electrical and vacuum connector, repair or replace as required.
2. Apply brake pedal and ensure brake lights work. On 1989-92 Aerostar, Bronco II, Explorer and Ranger models, if satisfactory, proceed to step 3. On models except 1989-92 Aerostar, Bronco II, Explorer and Ranger models, if satisfactory, proceed to step 4. If not satisfactory, check stop lamp circuit.
3. On 1989-92 Aerostar, Bronco II, Explorer and Ranger, depress horn pad, if horn sounds on manual transmission models, proceed to step 4, if horn sounds on automatic transmission models, proceed to step 5. If horn does not sound perform horn relay circuit test.
4. On all models, ensure proper operation of clutch deactivator switch (manual transmission only). If satisfactory, proceed to step 5. If not satisfactory, service or replace as necessary.
5. Ensure proper operation of actuator lever and throttle linkage. If satisfactory, proceed to step 6. If not satisfactory, adjust, connect, service or replace actuator lever and throttle linkage.
6. Ensure proper vacuum at actuator, 2.5 inch Hg (1.22 psi) minimum vacuum should be indicated for normal servo operation. on gasoline engines, the vacuum source is attached to 5/16 inch engine vacuum fitted port or on diesel engines, to the vacuum reservoir VAC port. If satisfactory, proceed to step 7. If not satisfactory, adjust, service or replace vacuum hose and vacuum dump valve.
7. Perform tests on control switches and circuit. If satisfactory, proceed to step 8. If not satisfactory, service or replace switches and circuits.
8. Perform tests on servo. If satisfactory, proceed to step 9. If not satisfactory, replace servo.
9. Perform tests on speed sensor. If satisfactory, proceed to step 10. If not satisfactory, replace speed sensor.
10. Perform tests on amplifier. If satisfactory, proceed to step 11. If not satisfactory, replace amplifier.
11. Examine all connectors to ensure proper contacts.