Pinpoint Test I: Temperature Control is Inoperative/Does Not Operate Correctly

Climate Control System

Pinpoint Test I: Temperature Control is Inoperative/Does Not Operate Correctly


Normal Operation

Under normal operation, the temperature blend door actuator is supplied voltage and ground. As the temperature selection changes the temperature control potentiometer varies the voltage to the temperature blend door actuator. The temperature control potentiometer receives reference voltage and ground from the temperature blend door actuator.

This pinpoint test is intended to diagnose the following:

- Fuse(s)

- Wiring, terminals or connectors

- Temperature blend door actuator

- Temperature control potentiometer

- Stuck or bound linkage or door

PINPOINT TEST I : TEMPERATURE CONTROL IS INOPERATIVE/DOES NOT OPERATE CORRECTLY

I1 CHECK THE VOLTAGE TO THE BLEND DOOR ACTUATOR

- Ignition OFF.

- Disconnect: Blend Door Actuator C289.

- Ignition ON.

- Measure the voltage between blend door actuator C289-7, circuit CBP37 (WH), harness side and ground.





Is the voltage greater than 10 volts?

Yes
GO to I2.

No
VERIFY the Smart Junction Box (SJB) fuse 37 (10A) is OK. If OK, REPAIR circuit CBP37 (WH) for an open. TEST the system for normal operation.

I2 CHECK THE GROUND TO THE BLEND DOOR ACTUATOR

- Ignition OFF.

- Measure the resistance between blend door actuator C289-8, circuit GD115 (BK/GY), harness side and ground.





Is the resistance less than 5 ohms?

Yes
GO to I3.

No
REPAIR circuit GD115 (BK/GY) for an open. TEST the system for normal operation.

I3 CHECK THE TEMPERATURE CONTROL LOW SIDE OPERATION

- Measure the resistance between blend door actuator C289-4, circuit CH203 (GN/BN), harness side and C289-3, circuit CH204 (GY/OG), harness side while rotating the temperature control switch from full WARM to full COOL.





Does the resistance vary from 20 ohms to 6,000 ohms?

Yes
GO to I6.

No
GO to I4.

I4 CHECK THE CIRCUIT FOR AN OPEN

- Disconnect: Temperature Control Switch C294D.

- Measure the resistance between temperature control switch C294D-3, circuit CH203 (GN/BN), harness side and blend door actuator C289-4, circuit CH203 (GN/BN), harness side.





Is the resistance less than 5 ohms?

Yes
GO to I5.

No
REPAIR circuit CH203 (GN/BN) for an open. TEST the system for normal operation.

I5 CHECK THE CONTROL CIRCUIT FOR AN OPEN

- Measure the resistance between temperature control switch C294D-2, circuit CH204 (GY/OG), harness side and blend door actuator C289-3, circuit CH204 (GY/OG), harness side.





Is the resistance less than 5 ohms?

Yes
INSTALL a new temperature control switch. TEST the system for normal operation.

No
REPAIR circuit CH204 (GY/OG) for an open. TEST the system for normal operation.

I6 CHECK THE TEMPERATURE CONTROL HIGH SIDE OPERATION

- Measure the resistance between blend door actuator C289-6, circuit CH202 (BU/GN), harness side and C289-3, circuit CH204 (GY/OG), harness side while rotating the temperature control switch from full WARM to full COOL.





Does the resistance vary from 20 ohms to 6,000 ohms?

Yes
GO to I8.

No
GO to I7.

I7 CHECK THE CIRCUIT FOR AN OPEN

- Disconnect: Temperature Control Switch C294D.

- Measure the resistance between temperature control switch C294D-1, circuit CH202 (BU/GN), harness side and blend door actuator C289-6, circuit CH202 (BU/GN), harness side.





Is the resistance less than 5 ohms?

Yes
INSTALL a new temperature control switch. TEST the system for normal operation.

No
REPAIR circuit CH202 (BU/GN) for an open. TEST the system for normal operation.

I8 CHECK THE CIRCUIT FOR A SHORT TO GROUND

- Disconnect: Temperature Control Switch C294D.

- Measure the resistance between temperature control switch C294D-3, circuit CH203 (GN/BN), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to I9.

No
REPAIR circuit CH203 (GN/BN) for a short to ground. TEST the system for normal operation.

I9 CHECK CONTROL CIRCUIT FOR A SHORT TO GROUND

- Measure the resistance between temperature control switch C294D-2, circuit CH204 (GY/OG), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to I10.

No
REPAIR circuit CH204 (GY/OG) for a short to ground. TEST the system for normal operation.

I10 CHECK THE CIRCUIT FOR A SHORT TO GROUND

- Measure the resistance between temperature control switch C294D-1, circuit CH202 (BU/GN), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to I11.

No
REPAIR circuit CH202 (BU/GN) for a short to ground. TEST the system for normal operation.

I11 CHECK FOR A BINDING, STUCK OR BROKEN BLEND DOOR

- Remove the blend door actuator.

- Inspect for a binding, stuck or broken blend door or linkage.

Is there a binding, stuck or broken blend door or linkage condition?

Yes
REPAIR the blend door/linkage. TEST the system for normal operation.

No
INSTALL a new temperature blend door actuator. TEST the system for normal operation.