Pneumatic Check
- Disconnect bead chain or rod and electrical connector at the servo unit. Start the engine. Apply 12 volts between A and C. Apply 12 volts between E and C. Servo should move full stroke. If not, check the vacuum hoses to the vacuum supply. Remove voltage from E and C.
- The servo should move a full stroke. If not, disconnect vacuum brake release at the servo and plug the servo. Momentarily apply 12 volts between E and C to allow the servo to full stroke. If the servo holds its position, adjust the brake vacuum release valve or replace the valve. If no defect is found in any of the tests, replace the electronic controller.