Test C: No Operation In All Temperature Settings

WARNING: This page is about a different car, the 1999 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

Check Electronic Blend Door Actuator Motor

Start engine and allow it to reach normal operating temperature. Place function selector switch in MAX A/C position. Adjust blend door potentiometer (temperature knob) to full COOL position. Check for cool air discharge. Adjust blend door potentiometer (temperature knob) to full WARM position. Check for warm air discharge. Vary blend door actuator control from full WARM to full COOL. If air temperature changed, system is okay at this time. If air temperature did not change, go to next step.

Check Voltage To Electronic Blend Door Actuator Motor

Turn ignition off. Disconnect electronic blend door actuator motor connector. Turn ignition to run position (engine off). Measure voltage between electronic blend door actuator motor connector Light Blue/Pink wire terminal and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open circuit in Light Blue/Pink wire. Retest system.

Check Red/Light Green, Yellow/Light Green & Red/White Wire Circuits For Open

Turn ignition off. Disconnect blend door actuator control connector. Measure resistance between blend door actuator control connector terminals and electronic blend door actuator motor connector terminals. See ACTUATOR CONTROL & ACTUATOR MOTOR RESISTANCE CHECK table. If resistances are less than 5 ohms, go to next step. If resistances are greater than 5 ohms, repair wiring as necessary. Retest system.

ACTUATOR CONTROL & ACTUATOR MOTOR RESISTANCE CHECK

Actuator Control Terminal No. (Wire Color)	Actuator Motor Terminal No.
3 (Red/Light Green)	4
2 (Yellow/Light Green)	3
1 (Red/White)	6

Check Red/Light Green, Yellow/Light Green & Red/White Wire Circuits For Short

Measure resistance between ground and blend door actuator control connector Red/Light Green, Yellow/Light Green, and Red/White wires. If resistances are greater than 10,000 ohms, go to next step. If resistances are not greater than 10,000 ohms, repair wiring as needed. Retest system.

Check A/C Control Potentiometer

Measure resistance between blend door actuator control terminal No. 2 (Yellow/Light Green wire) and terminal No. 3 (Red/Light Green wire). If resistance is 4,000 ohms when blend door actuator control is in full COOL position and 200 ohms or less when blend door actuator is in full WARM position, replace electronic door actuator motor. Retest system. If resistance is not as specified, replace blend door actuator control. Retest system.