Pinpoint Test W: The Temperature Control Is Inoperative Using The Front Auxiliary Climate Controls

WARNING: This page is about a different car, the 2004 Mercury Mountaineer and 2004 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

W1 CHECK VOLTAGE TO BLEND DOOR ACTUATOR
- Disconnect: Auxiliary Temperature Blend Door Actuator C3019.
- Key in ON position.
- Measure the voltage between the auxiliary temperature blend door actuator C3019-7, circuit 1003 (GY/YE) and ground.
  
  Fig 1: Checking Voltage To Blend Door Actuator
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes

GO to W2.

No

REPAIR circuit 1003 (GY/YE). TEST the system for normal operation.
W2 CHECK THE BLEND DOOR ACTUATOR GROUND CIRCUIT FOR AN OPEN
- Key in OFF position.
- Measure the resistance between the auxiliary temperature blend door actuator C3019-8, circuit 1205 (BK) and ground.
  
  Fig 2: Checking Blend Door Actuator Ground Circuit For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes

GO to W3.

No

REPAIR circuit 1205 (BK). TEST the system for normal operation.
W3 CHECK THE TEMPERATURE BLEND DOOR ACTUATOR SIGNAL
- Key in ON position.
- Place the front auxiliary blower motor switch in HI.
- Measure the voltage between the auxiliary temperature blend door actuator C3019-3, circuit 1125 (BN) and ground. Rotate the temperature control switch to full COOL then to full WARM.
  
  Fig 3: Checking Temperature Blend Door Actuator Signal
  Courtesy of FORD MOTOR CO.
- Does the voltage vary from greater than 10 volts (full COOL) to less than 1 volt (full WARM)?
Yes

Check for a broken/binding auxiliary temperature blend door. If OK, INSTALL a new auxiliary temperature blend door actuator. REFER to TEMPERATURE BLEND DOOR ACTUATOR - AUXILIARY . TEST the system for normal operation.

No

GO to W4.
W4 CHECK CIRCUIT 1125 (BN) FOR AN OPEN
- Key in OFF position.
- Disconnect: Front Auxiliary Climate Control Assembly C938a.
- Measure the resistance between the front auxiliary climate control assembly C938a-3, circuit 1125 (BN) and the auxiliary temperature blend door actuator C3019-3, circuit 1125 (BN).
  
  Fig 4: Checking Circuit 1125 (BN) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes

INSTALL a new front auxiliary climate control assembly. REFER to AUXILIARY CLIMATE CONTROL ASSEMBLY - FRONT . TEST the system for normal operation.

No

REPAIR circuit 1125 (BN). TEST the system for normal operation.