Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .
Blower Motor Inoperative
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Turn ON the ignition. Observe the temperature indication screen of the controller. Does the digit flash? | Go to Step 2 | Go to Step 3 | |
| 2 | Run a self-diagnosis circuit check. Does the display indicate a defect code? | Go to appropriate DTC table | ||
| 3 | Turn ON the ignition. Measure the voltage between ground and terminal 2 of the blower motor. Does the voltage measure within the specified value? | 11-14 V | Go to Step 4 | Go to Step 5 |
| 4 | Measure the voltage between ground and terminal B12 at the ACT switch. Does the voltage measure within the specified value? | 11-14 V | Go to Step 6 | Go to Step 12 |
| 5 | Repair any problem found in terminal 2 at the blower motor circuit or ground G203. Did you complete the repair? | System OK | ||
| 6 | Measure the resistance between the connector terminals on the blower motor. Does the resistance measure equal to the specified value? | 5 ohms | Go to Step 8 | Go to Step 7 |
| 7 | Replace the blower motor. Did you complete the repair? | System OK | ||
| 8 | Turn OFF the ignition. Using an ohmmeter, measure the resistance between terminal 1 of the blower motor and terminal 2 of the power transistor. Does the resistance measure equal to the specified value? | 0 ohms | Go to Step 10 | Go to Step 9 |
| 9 | Repair the circuit between terminal 1 of the blower motor and terminal 2 of the power transistor. Did you complete the repair? | System OK | ||
| 10 | Measure the resistance between terminal 2 of the power transistor connector to ground Does the resistance measure equal to the specified value? | 0 ohms | Go to Step 11 | Go to Step 12 |
| 11 | Trace the circuit from terminal 2 of the power transistor connector to ground G203. Repair any problem found in the circuit to ground G203. Did you complete the repair? | System OK | ||
| 12 | Replace the ATC controller. Did you complete the repair? | System OK |
Too Hot in Vehicle
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic Trouble Code (DTC) List - Vehicle |
| 2 | Observe the blower motor operation. Is the blower motor functioning at all? | Go to Step 3 | Go to Blower Motor Inoperative |
| 3 | Use the blower push switch to cycle the blower through its different speeds. Does the motor function at different speeds? | Go to Step 4 | Go to Blower Motor Inoperative |
| 4 | Run the blower and the operate the MODE push switch manually. Inspect for airflow out the various outlets. Does the air flow from the different outlets as it should? | Go to Step 6 | Go to Step 5 |
| 5 | Remove the heater outlet and inspect for obstructions. Remove any obstructions found. Is the heater operating? | System OK | Go to Step 8 |
| 6 | Observe the air mix door motor (AMD) while changing the temperature setting from 18-32°C (64-90°F) and then from 32-18°C (90-64°F). Is the AMD motor functioning properly? | Go to Step 7 | Go to DTC 4 |
| 7 | Perform the checks found in HVAC preliminary checks. Refer to HVAC Preliminary Checks . Is the system operating normally now? | System OK | Go to Step 8 |
| 8 | Place the controller in the AUTO mode. Inspect for airflow through the inside air temperature assembly by placing a 5 cm (2 in) square piece of paper over the sensor air inlet. Does the paper stay in place? | Go to Step 11 | Go to Step 9 |
| 9 | Inspect the intake hose for the in-car sensor. Is the hose in good condition? | Go to Step 11 | Go to Step 10 |
| 10 | Repair or replace the intake hose. Is the repair complete? | System OK | |
| 11 | Inspect the in-car sensor. Refer to DTC 1 . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 12 | Go to Step 13 |
| 12 | Repair or replace the sensor, the wiring, or the controller as required. Is the repair complete? | System OK | |
| 13 | Inspect the ambient air temperature sensor. Refer to DTC 2 . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 14 | Go to Step 15 |
| 14 | Repair or replace the sensor, the wiring, or the controller, as required. Is the repair complete? | System OK | |
| 15 | Inspect the sun sensor. Refer to DTC 5 . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 14 | Go to Step 16 |
| 16 | Perform the coolant temperature sensor test. Is the coolant temperature sensor malfunctioning? | Go to Step 17 | Go to Step 18 |
| 17 | Replace the coolant temperature sensor. Is the repair complete? | System OK | |
| 18 | Replace the air temperature controller (ATC). Refer to Heater and Air Conditioning Control Replacement . Is the repair complete? | System OK |
Too Cold in Vehicle
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic Trouble Code (DTC) List - Vehicle |
| 2 | Inspect the coolant level. Is the coolant level correct? | Go to Step 4 | Go to Step 3 |
| 3 | Add coolant as needed. Did you correct the condition? | System OK | |
| 4 | Observe the blower motor operation. Is the blower motor functioning at all? | Go to Step 5 | Go to Blower Motor Inoperative |
| 5 | Use the blower push switch to cycle the blower through its different speeds. Does the motor function at different speeds? | Go to Step 6 | Go to Blower Motor Inoperative |
| 6 | Run the blower and operate the MODE push switch manually. Check for airflow out the various outlets. Does the air flow from the different outlets as it should? | Go to Step 8 | Go to Step 7 |
| 7 | Remove the heater outlet and inspect for obstructions. Remove any obstructions found. Is the heater operating? | System OK | Go to Step 8 |
| 8 | Observe the air mix door (AMD) motor while changing the temperature setting from 18-32°C (64-90°F) and then from 32-18°C (90-64°F). Is the AMD motor adjusting to temperature properly? | Go to Step 9 | Go to DTC 4 |
| 9 | Inspect the coolant hoses for leaks or kinks. Are the coolant hoses in good condition? | Go to Step 11 | Go to Step 10 |
| 10 | Repair any problem with the coolant hoses. Is the heater operating? | System OK | Go to Step 11 |
| 11 | Inspect the surge tank cap. Is the surge tank cap in good condition? | Go to Step 13 | Go to Step 12 |
| 12 | Repair or replace the surge tank cap as needed. Is the heater operating? | System OK | Go to Step 13 |
| 13 | Set the A/C switch to OFF. Set the temperature control to 32°C (90°F). Set the blower motor speed to full high, all segments illuminated on the display. Remove the surge tank cap. Start the vehicle and run the engine at idle. Watch for the flow of the coolant when the thermostat opens. Does the coolant flow? | Go to Step 15 | Go to Step 14 |
| 14 | Inspect for the following conditions: A faulty thermostat A failed coolant pump impeller A restriction in the cooling system Make repairs as needed. Is the repair complete? | System OK | |
| 15 | Inspect the temperature of the heater inlet and outlet hoses by feel. Is the heater inlet hose hot and the outlet hose warm? | Go to Step 17 | Go to Step 16 |
| 16 | Back flush or replace the heater core. Is the repair complete? | System OK | |
| 17 | Inspect the vehicle for cold air leaks at the following locations: Dash Heater cases Vents Are any leaks found? | Go to Step 19 | Go to Step 18 |
| 18 | Repair any cold air leaks. Is the repair complete? | System OK | |
| 19 | Inspect the coolant temperature sensor. Is there a problem indicated in the sensor, the sensor wiring or the controller? | Go to Step 20 | Go to Step 21 |
| 20 | Repair or replace the sensor, the wiring, or the controller as required. Is the repair complete? | System OK | |
| 21 | Inspect the in-car sensor. Refer to DTC 1 . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 20 | Go to Step 22 |
| 22 | Inspect the ambient air temperature sensor. Refer to DTC 2 . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 20 | Go to Step 23 |
| 23 | Inspect the sun sensor. Refer to DTC 5 . Is there a problem indicated in the sensor, the sensor wiring, or the controller? | Go to Step 20 | Go to Step 24 |
| 24 | Replace the automatic temperature controller (ATC). Refer to Heater and Air Conditioning Control Replacement . Is the repair complete? | System OK |
Control Head Inoperative
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Check the fuse F19. Is the fuse open? | Go to Step 2 | Go to Step 3 | |
| 2 | Repair any short circuit and replace the open fuses. Did you complete the repair? | System OK | ||
| 3 | Remove the controller. Turn ON the ignition. Measure the voltage between terminal B2 and B3 of the connectors. Does the voltage measure within the specified value? | 11-14 V | Go to Step 4 | Go to Step 5 |
| 4 | Inspect the connector and controller for damages. Repair the damaged parts or replace the controller. Did you complete the repair? | System OK | ||
| 5 | Measure the voltage between terminal B13 of the connector and ground. Does the resistance measure equal to the specified value? | 0 V | Go to Step 6 | Go to Step 7 |
| 6 | Inspect the wiring harness between fuse F19 and the terminal B2 for damage. Replace the wiring harness if it is damaged. Did you complete the repair? | System OK | ||
| 7 | Inspect the wiring harness between terminal B3 and ground G203 for damage. Repair the wiring harness, or ground connection as required. Did you complete the repair? | System OK |
Controller
The operation of the A/C system is controlled by the switches on the control head. This console-mounted heating and ventilation system consists of control knobs and a vacuum fluorescent display (VFD) indicating the status of the control settings selected.
Temperature Control Push Knobs
- Raise the temperature of the air entering the vehicle by turning the rotary switch clockwise (red arrow direction).
- Lower the temperature of the air entering the vehicle by turning the switch counterclockwise (blue arrow direction).
- Actuate the air mix door by an electric motor.
- Vary the mix of the air passing through the heater core with the air bypassing the core.
- Each press of a switch changes the set temperature by increments of 0.5°C (1°F). This is shown in the temperature window on the function display.
Vacuum Fluorescent Display (VFD)
- Temperature setting-Indicates the temperature set with temperature control knob.
- Auto status-Indicated whether the system is operating in the full automatic mode or manual mode.
- Defroster icon-Indicates manual selection of full defrost mode.
- Mode-Indicated by icon, the mode chosen by the system in auto (or by the operator in manual) is shown by an illumination arrow indicating the air path.
- A/C-A snowflake icon indicating whether the A/C is ON or OFF.
- Fan speed-Indicates the fan speed by illuminating a bar based on the segment at the front, for low speed, and adding additional segments in order up to the eighth, for high speed.
Seven Additional Push Knobs
- Full defrost-Causes the mode motors to direct all air to the windshield and aide window outlets for maximum defrosting.
- Air intake-Switches between fresh air intake, the default, and recirculating air. Airflow arrows on the display indicate the mode in effect.
- Full auto switch-Maintains the set temperature automatically. In this mode, the fully automatic temperature control (FATC) system controls the following: The air mix door motor The mode door motor The blower motor speed The inlet air door motor A/C ON/OFF
- OFF switch-Turns the automatic air conditioning and fan control off.
- Mode switch-Allows manual selection of the airflow direction. Selection is shown on the function display. Each time the mode switch is pressed, the next function is displayed.
- A/C switch-Allows manual selection and control of the air conditioning function.
- Defogger switch-Turns ON the electric defogging heater in the rear window and the outside rearview mirrors, if the vehicle is equipped with heated mirrors.
- Fan control rotary knob-Allows for manual selection of the fan speed.
Pressure Transducer
Pressure transducer switching incorporates the functions of the high-pressure and the low-pressure cutout switches along with the fan cycling switch. The pressure transducer is located in the high-side liquid refrigerant line behind the right strut tower, between the right strut tower and the front of dash. The output from this pressure transducer goes to the electronic control module (ECM), which controls the compressor function based on the pressure signal.
Wide-Open Throttle (WOT) Compressor Cutoff
During full-throttle acceleration, the throttle position (TP) sensor sends a signal to the ECM, which then controls the compressor clutch.
High RPM Cutoff
As engine RPM approached the maximum limit, the ECM will disengage the compressor clutch until the engine slows the a lower RPM.