This 2007 Lincoln Town Car came in with the complaint that sometimes the a/c air would not blow out of the face vent. Instead the air would flow from the defrost and floor vents. Sometimes the air would start flowing from the face vents a few seconds after turning the ignition on but would soon move to the defroster and floor locations. Almost like the system was hunting for a signal that it could not find. Testing with a scan tool found no codes stored in the EATC system, Electronic Automatic Temperature Control system.
Manual testing was needed. The dash face trim panel has to be removed first. There are two screws with 7 mm heads along the upper edge of the instrument cluster panel as shown below.
Then the panel can be grasped on the edges around the vents so that it can be pulled free of the dash. I found it easier to start at this location and then work my way back across to the driver’s side of the panel. The steering column will need to be tilted fully down and the gear selector placed in the drive one position.
There are several switches that have to be disconnected once the panel is pulled far enough out. Again I found it easier to work from the far right side and come back to the driver’s side as more room is gained. All of the harness connectors have thumb latches securing them. The latches have to be depressed before trying to pull the harness connectors from the switches.
The headlights will come on a stay once the headlight switch is disconnected. Since that battery needs to stay connected to perform testing I found it best to unscrew the headlight switch from the dash trim panel and reconnect it to the harness. There are three 5.5 mm headed screws that hold it in place.
With the headlight switch reconnected and positioned out of the way the headlights turned back off.
There are four screws that hold the EATC control panel in place. They all have 7 mm heads.
Voltage testing can be done by backprobing the wiring harness connectors at the proper locations.
The smaller connector body is connector C228B and the larger connector body is connector C228A. The actuator motor control wires are located in connector C228A. The sensor five volt reference signal, ground and position circuits are located in connectors C228A and C228B.
The five volt reference for all five of the actuators is supplied from terminal 8, Red/Green wire of the C228B connector.
The return or ground signal is supplied from terminal 20, Red/White wire of the C228A connector.
The feedback or position signals are located in the following positions.
- Panel/Defrost Mode Actuator terminal 15, Yellow/White wire connector C228B.
- Floor Mode Actuator terminal 14, Pink/Light Green wire connector C228B.
- Driver’s Temperature Blend Door Actuator terminal 4, Yellow/Light Green Wire connector C228B.
- Passenger’s Temperature Blend Door Actuator terminal 5, Red wire connector C228B.
- Fresh Air/Recirculation Door Actuator terminal 3, Yellow/Light Blue wire connector C228B.
The voltage signals for the actuator position signals are nominally as follows.
- Panel/Defrost Mode Actuator 3.45 volts at full face or split face settings. 1.28 volts and any other setting.
- Floor Mode Actuator 1.47 volts at defrost, 1.68 volts at vent, 2.17 volts at bi-level, 2.19 volts at defrost/floor and 2.61 volts at full floor position.
- Driver’s Temperature Blend Door Actuator 4.26 volts at full cold and .825 volts at full hot.
- Passenger’s Temperature Blend Door Actuator .27 volts at full cold and 3.58 volts at full hot.
- Fresh Air/Recirculation Door Actuator 4.3 volts at fresh air position and 1.0 volts at full recirculation.
All voltage readings should have a smooth varying voltage as the actuator is commanded through it’s full range of travel. Chassis ground should be used for the ground lead of the voltmeter.
The actuator motor control circuits are located in the following positions in the C228A connector.
- Panel/Defrost Mode Actuator terminal 24, Pink/Light Blue wire and terminal 25, Tan/Yellow wire.
- Floor Mode Actuator terminal 22, Pink/Yellow wire and terminal 23, Black/Light Blue wire.
- Driver’s Temperature Blend Door Actuator terminal 13, Violet wire and terminal 26, Brown/Light Green wire.
- Passenger’s Temperature Blend Door Actuator terminal 11, White wire and terminal 12, Brown wire.
- Fresh Air/Recirculation Door Actuator terminal 9, Orange/Light Blue wire and terminal 10, Yellow/Light Green wire.
When commanded to move the motor wires for an individual actuator motor will have a nominal 10 volt reading across both the the selected terminals. The polarity will reverse as the actuator is commanded in the opposite direction. It may be of interest to know that a 9 volt transistor style battery with leads attached to it can be used to drive the motors with the control head disconnected.
On this vehicle there were very erratic readings on both of the mode actuators position sensor signal wires. The reading of the Panel/Defrost actuator would go open at times. Time to man up and pull this dash.
The next step will be to remove the steering column from the car.