Intrepid V6-215 3.5L (1995)
Air Door Actuator / Motor: Description and Operation
Automatic Temperature Control (ATC)
TROUBLE CODES
The Diagnostic Readout Box (DRB) trouble codes that indicate a stall failure or a feedback signal failure work together to show what is wrong
with the Automatic Temperature Control (ATC) system.
PROBLEM LOCATION
The stall trouble codes mean that the body control module cannot force an actuator to the end of the ATC-heater unit door. Internal problems in
the body control module will set other short-related trouble codes. Having only stall trouble codes indicates that there is a problem with an open or
short circuit in the wiring, a bad actuator, a bad ATC-heater unit door or connecting linkage. It is important that the operation of the ATC-heater
unit door be checked if an actuator is removed. This can be checked by rotating each unit door shaft to confirm that the door will stop at both ends
of travel. The actuator itself has no stops. It must have the ATC-heater unit door to stop travel to pass the stall test.
FEEDBACK SIGNAL FAILURE
A feedback signal failure can occur on the blend or mode door. The body control module monitors the feedback signal to check the position of the
actuator. The body control module not only checks the level of the signal but also how much the voltage changes.
CAUSE OF FAILURE
A feedback failure can occur if there is a short or open circuit in the wiring, a bad actuator, a bad body control module, a bad ATC-heater unit
door or connecting linkage. The easiest way to diagnose this is to use the DRB to actuate the blend or mode door. Note that the feedback voltage
of the actuator should smoothly change as the actuator is moved. A sudden change in the feedback voltage to a 5.0-volt or a 0.0-volt level indicates
the actuator is bad. A fixed feedback voltage that is less than 5.0 volts or greater than 0.0 volts without a stall failure, or a short failure indicates
that the actuator, the ATC-heater unit door, or a connecting mechanical linkage is jammed preventing movement. A feedback signal voltage that
stays on 5.0 volts or 0.0 volts indicates a wiring or body control module problem.
DOOR MOVEMENT
The feedback failure trouble code can also occur from a lack of actuator travel. This can be checked by confirming that the feedback signal
smoothly changes when the actuator is moved with the DRB. If the signal is OK, the door travel is not correct. The actuator must be removed and
the ATC-heater unit door mechanically checked for proper operation. Typical problems that prevent door movement include screws dropped in the
ATC-heater unit or warped doors. Replace any part that is found defective.
