Mode Lockup

Affected Vehicles: 1988-89 C/K series GM Trucks

A problem known as "Mode Lockup" occurs on 1988-89 C/K series GM trucks. This will happen when the system will not come out of Heat or A/C mode when another mode is requested. An improved mode door actuator has now been released. "Mode Lockup" is caused by dirty actuator contacts. Installing a new actuator will correct this condition. The new actuator is quieter with improved response time.
Original installed mode actuators will have either a white or yellow label. Replace either of these with a blue label O.E. unit, General Motors part # 16141802.

Installation Instructions:

A. Disconnect or Unplug the following:

1. Battery ground
2. Actuator electrical connection.
3. Linkage
4. Mode actuator.

B. Install new actuator

C. Adjust new actuator:

1. Install battery ground cable and electrical connection to actuator.
2. Turn the ignition key to run and let the actuator position itself.
3. Turn off ignition key.
4. Disconnect the electrical connection to the actuator and the battery ground.

D. Reconnect the following:

1. Mode actuator.
2. Linkage
3. Electrical connection to actuator
4. Instrument panel.
5. Battery ground.