HVAC Schematic Icons
HVAC Schematic Icons Icon Icon Definition CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs
Scheme 1
Scheme 2
Scheme 3
Scheme 4
Scheme 5
Scheme 6
| Callout | Component Name |
|---|---|
| 1 | A/C Condenser |
| 2 | A/C Compressor |
| 3 | A/C Compressor Clutch |
| 4 | A/C Refrigerant Pressure Sensor |
Scheme 7
| Callout | Component Name |
|---|---|
| 1 | Coolant Level Switch |
| 2 | Coolant Recovery Reservoir |
Scheme 8
| Callout | Component Name |
|---|---|
| 1 | Ambient Air Temperature Sensor Connector |
| 2 | Ambient Air Temperature Sensor |
| 3 | Instrument Panel Cluster (IPC) (LHD shown, RHD similar) |
| 4 | Radio |
| 5 | HVAC Control Module |
| 6 | Sunload Sensor Connector |
| 7 | Speaker - Front Center (U57) |
| 8 | Radio |
| 9 | Sunload Sensor |
| 10 | Trim Panel - I/P Center |
Scheme 9
| Callout | Component Name |
|---|---|
| 1 | Mode Actuator |
| 2 | Evaporator Temperature Sensor |
| 3 | C214 |
| 4 | Recirculation Actuator |
| 5 | C200 |
| 6 | Blower Motor |
| 7 | Blower Controller |
| 8 | Air Temperature Actuator - Front Passenger |
| 9 | Thermostatic Expansion Valve |
| 10 | HVAC Control Module Mode Switch - Rear Auxiliary |
| 11 | HVAC Control Module Temperature Switch - Rear Auxiliary |
| 12 | Mode Actuator - Auxiliary |
| 13 | HVAC Box |
| 14 | Air Temperature Actuator - Rear Passenger |
| 15 | Air Temperature Actuator - Driver |
Scheme 10
| Callout | Component Name |
|---|---|
| 1 | Dash Board |
| 2 | Instrument Panel Cluster (IPC) |
| 3 | Ignition Mode Switch |
| 4 | Air Temperature Sensor - Inside |
| 5 | I/P Dimmer Switch/HUD Switches w/ UV6 |
Scheme 11
| Callout | Component Name |
|---|---|
| 1 | Air Quality Sensor (K14) |
| 2 | Ambient Air Temperature Sensor |
| 3 | Hood Ajar Switch Connector |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 6: The ambient air temperature must be above 3°C (38°F) for this A/C compressor test.
- 7: The specified values are from the A/C System Performance Test.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The temperature cannot be adjusted, or cooling is insufficient during A/C operation. | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | Place the blower motor switch in each speed position. Does the blower motor operate in any speed position? | Go to Step 3 | Go to Blower Motor Inoperative | |
| 3 | Does the blower motor operate at the desired speeds? | Go to Step 4 | Go to Blower Motor Malfunction | |
| 4 | Start the engine. Place the mode switch in the panel position. Place the recirculation switch in the ON position. Observe the recirculation door. Place the recirculation switch in the OFF position. Does the recirculation door move from the recirculation position to the outside air position? | Go to Step 5 | Go to Air Recirculation Malfunction | |
| 5 | Does the customer concern occur when the air conditioning is ON? | Go to Step 6 | Go to Step 8 | |
| 6 | IMPORTANT: The ambient air temperature must be above 3°C (38°F). Start the engine. Place the left air temperature switch in the coldest position. Place the mode switch in the bi-level position. Place the A/C request switch to the ON position. Does the A/C compressor operate? | Go to Step 7 | Go to HVAC Compressor Clutch Does Not Engage | |
| 7 | Perform the A/C system performance test. Refer to Air Conditioning (A/C) System Performance Test (LH2 w/ Standard Cooling) or Air Conditioning (A/C) System Performance Test (LY7 w/Standard Cooling) or Air Conditioning (A/C) System Performance Test (LH2 w/ Heavy Duty Cooling) or Air Conditioning (A/C) System Performance Test (LY7 w/ Heavy Duty Cooling) in Heating, Ventilation, and Air Conditioning. Did you find and correct the condition? | Go to Step 25 | Go to Step 8 | |
| 8 | Inspect the inside air temperature sensor for proper installation. Refer to Inside Air Temperature Sensor Replacement . Did you find and correct the condition? | Go to Step 25 | Go to Step 9 | |
| 9 | Turn ON the ignition with the engine OFF. Place the mode switch in panel position. Place the blower motor switch in maximum speed position. Inspect for airflow through the inside air temperature sensor 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 10 | Go to Step 16 | |
| 10 | Install a thermometer near the inside air temperature sensor. With a scan tool, observe the Inside Air Temp parameter in the Climate Control Panel data list. Does the scan tool indicate the sensor temperatures is within 3°C (5°F) of the thermometer temperature? | Go to Step 11 | Go to Step 14 | |
| 11 | Turn OFF the ignition. Cover the sunload sensor. Start the engine. Adjust driver side temperature to 22°C (72°F). With a scan tool, observe the Driver and Passenger Solar Sensor parameter in the Climate Control Panel Open/Short data list. Is the Solar Sensor parameter greater than the specified value? | 220 Counts | Go to Step 12 | Go to Step 19 |
| 12 | Uncover the sunload sensor. Direct a light source at the sunload sensor. Observe the Driver and Passenger Sunload parameter. Do the counts change? | Go to Step 13 | Go to Step 19 | |
| 13 | Test the resistance of the ambient air temperature sensor. Refer to LINK 48912. Is the resistance near the value in the Sensor Resistance Table? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 15 | |
| 14 | Test the resistance of the inside air temperature sensor. Refer to LINK 48912. Is the resistance near the value in the Sensor Resistance Table? | Go to Step 20 | Go to Step 18 | |
| 15 | Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 17 | |
| 16 | Inspect the aspirator tube for a air leak or obstruction. Did you find and correct the condition? | Go to Step 25 | ||
| 17 | Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 | |
| 18 | Inspect for poor connections at the harness connector of the inside air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 21 | |
| 19 | Inspect for poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 22 | |
| 20 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 24 | |
| 21 | Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 25 | ||
| 22 | Replace the sunload sensor. Refer to Sun Load Sensor Replacement . Did you complete the replacement? | Go to Step 25 | ||
| 23 | Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 25 | ||
| 24 | Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 25 | ||
| 25 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 | |
| IMPORTANT |
|---|
| The ambient air temperature must be above 3°C (38°F). |
Too Hot in Vehicle
Air Delivery Description and Operation
The Air Delivery Description and Operation is divided into 5 primary areas
- HVAC Control Components
- Air Speed
- Air Speed Auxiliary
- Air Distribution
- Recirculation
- Automatic Operation
Automatic Operation
In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.
To place the HVAC system in full automatic operation, the AUTO selection must be activated.
Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically adjust to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature
- Regulate blower motor speed
- Position the air temperature actuator
- Position the mode actuator
- Position the recirculation actuator
- Request A/C operation
When the warmest position is selected in automatic operation the blower speed will increase gradually until the vehicle reaches normal operating temperature. When normal operating temperature is reached the blower will stay on high speed and the air temperature actuators will stay in the full heat position. The mode actuator will remain in the floor position.
When the coldest position is selected in automatic operation the blower will stay on high and the air temperature actuators will stay in the full cold position. The mode actuator will remain in the panel position and the recirculation actuator will remain in the recirculation position.
In cold temperatures, the automatic HVAC system will provide heat in the most efficient manner. The vehicle operator can select an extreme temperature setting, but the system will not warm the vehicle any faster. In warm temperatures, the automatic HVAC system will also provide air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.
Air Temperature Description and Operation
The air temperature controls are divided into 4 primary areas
- Automatic Operation
- The Heating and Air Conditioning System
- The A/C Cycle
- Auxiliary heating and A/C system
Heating and A/C Operation
The purpose of the heating and A/C system is to provide the following
- Heated air
- Cooled air
- Remove humidity from the interior of the vehicle
- Reduce windshield fogging
Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve a desired temperature
- Recirculation actuator setting
- Difference between inside and desired temperature
- Difference between ambient and desired temperature
- Blower motor speed setting
- Mode setting
The HVAC control module commands or monitors the following actions when an air temperature setting is selected.
- WARMEST POSITION-The air temperature actuator door position directs maximum air flow through the heater core.
- COLDEST POSITION-The air temperature actuator door position directs maximum air flow around the heater core.
- BETWEEN THE WARMEST AND COLDEST POSITION-The following sensors are monitored to direct the appropriate amount of air through the heater core to achieve the desired temperature: Sunload Ambient temperature Inside temperature
The A/C system is engaged by selecting any switch on the HVAC control module except the A/C OFF switch. The A/C switch will illuminate A/C OFF when the A/C switch is selected. The control module sends a class 2 A/C request message to the engine control module (ECM) for A/C compressor clutch operation. The following conditions must be met in order for the ECM to turn on the compressor clutch
- HVAC control module Evaporator Temperature more than 4°C (39°F) Control module operating range 9-16 volts
- ECM Engine coolant temperature (ECT) is less than 125°C (257°F) or 120°C (248°F) for PV8 Engine RPM is between 0-6,000 RPM. A/C pressure is between 3 137 kPa (455 psi) or 2 850 kPa (413 psi) for PV8 and 193 kPa (28 psi) or 200 kPa (29 psi) for PV8.
Once engaged, the compressor clutch will be disengaged for the following conditions
- Throttle position is 100 percent.
- A/C pressure is more than 3 137 kPa (455 psi) or 2 850 kPa (413 psi) for PV8.
- A/C pressure is less than 193 kPa (28 psi) or 200 kPa (29 psi) for PV8.
- Engine coolant temperature (ECT) is more than 125°C (257°F) or 120°C (248°F) for PV8.
- Engine speed is more than 5,500 RPM.
- Transmission shift
- ECM detects excessive torque load.
- ECM detects insufficient idle quality.
- ECM detects a hard launch condition.
When the compressor clutch disengages, the compressor clutch diode protects the electrical system from a voltage spike.
Dual Zone Operation
The HVAC control module has temperature settings for the driver and the passenger. If the passenger setting is turned OFF then the driver setting controls both driver and passenger temperature actuators. The passenger setting cannot be used without the driver setting also being ON. The passenger setting can be turned ON or OFF by pressing the power button in the center of the passenger temperature rocker switch. When the passenger setting is ON, the passenger temperature can be adjusted independently from the driver setting and the passenger temperature is displayed on the passenger side of the control module. A different sunload on one side of the vehicle may cause different discharge air temperatures, even when the passenger setting is not turned ON.
In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.
To place the HVAC system in automatic mode, the following is required
- The blower motor switch must be in the AUTO position.
- The air temperature switch must be in any other position other than 60 or 90 degrees.
- The mode switch must be in the AUTO position.
Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically adjust to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature
- Regulate blower motor speed
- Position the air temperature actuator
- Position the mode actuator
- Position the recirculation actuator
- Request A/C operation
When the warmest position is selected in automatic operation, the blower speed will increase gradually, until the vehicle reaches normal operating temperature. When normal operating temperature is reached, the blower will stay on high speed and the air temperature actuators will stay in the full heat position. When the coldest position is selected in automatic operation, the blower will stay on high and the air temperature actuators will stay in the full cold position.
In cold temperatures, the automatic HVAC system will provide heat in the most efficient manner. The vehicle operator can select an extreme temperature setting, but the system will not warm the vehicle any faster. In warm temperatures, the automatic HVAC system will also provide air conditioning in the most efficient manner. Selecting an extremely cool temperature will not cool the vehicle any faster.
Auxiliary Heating and A/C Operation
The auxiliary HVAC control module provides airflow direction and temperature control for the back seat passengers. Passengers can operate the rear HVAC control module in both manual or automatic modes. Auxiliary HVAC temperatures can be set cooler or warmer than the front primary HVAC setting. The front HVAC module provides power and ground to the auxiliary air temperature actuator. The front HVAC module receives power through the ignition 1 and battery positive voltage circuits from the underhood fuse block. The auxiliary air temperature actuator is a reverse polarity motor. Each circuit provides both power and ground to the auxiliary air temperature actuator. When the auxiliary air temperature actuator is being held in position, both of the auxiliary air temperature door control circuits have 0 volts applied to both sides of the actuator motor. This holds the actuator stationary. When a cooler temperature is requested, one of the auxiliary air temperature door control circuits will ground, driving the auxiliary air temperature actuator to the desired temperature. When a warmer temperature is requested, the other auxiliary air temperature door control circuit will ground. This moves the auxiliary air temperature actuator into the desired position.