Automatic Transmission/Transaxle: Testing and Inspection

Vehicles With Computerized Engine Controls





The electrical system used to control the activation and deactivation of the converter clutch on vehicles equipped with computerized engine controls consists of a solenoid and 3rd clutch pressure switch located in the auxiliary valve body and a brake release switch, electronic control module, throttle position sensor, vehicle speed sensor and either a vacuum or engine coolant temperature sensor mounted externally of the transaxle. The electronic control module receives information from the various sensors and, when vehicle speeds high enough, provides a ground for the solenoid, which activates the converter clutch. When operating conditions such as heavy acceleration indicate that the converter clutch be disengaged, the electronic control module removes ground from the solenoid and deactivates the system. The brake release switch opens the circuit and deactivates the converter clutch whenever the brakes are applied to prevent engine stalling. A converter clutch relay is used to assist in the activation and deactivation of the converter clutch.

Before attempting to diagnose converter clutch electrical problems, mechanical checks such as linkage adjustments and oil level should be performed and corrected, if necessary.

Vehicles Less Computerized Engine Controls








The electrical system used to control the activation and deactivation of the converter clutch on vehicles not equipped with computerized engine controls consists of a solenoid, 3rd clutch pressure switch and a governor pressure switch located in the auxiliary valve body, see images, and a brake release switch, thermal vacuum valve, engine vacuum switch, vacuum delay valve and ported vacuum mounted externally of the transaxle. The brake release switch opens the circuit and deactivates the converter clutch whenever the brakes are applied to prevent engine stalling. The thermal vacuum valve prevents the converter clutch from applying until the engine coolant temperature reaches approximately 130°F. The engine vacuum switch releases the converter clutch when engine vacuum drops to approximately 1.5-3 inches during moderate acceleration, prior to a part throttle or detent downshift The vacuum delay valve slows the vacuum switch response to vacuum changes and ported vacuum is the source of vacuum to the vacuum switch and opens the switch to release the clutch during a closed throttle coast down.

Before attempting to diagnose converter clutch electrical problems, mechanical checks such as linkage adjustments and oil level should be performed and corrected if necessary.