Process Description
The heater-A/C control diagnostic system check is an organized approach to identify problems associated with the heater-A/C control. This system check must be the starting point for any heater-A/C control complaint, and will direct you to the next logical step in diagnosing the trouble condition. The heater-A/C control is a very reliable component and is not likely the cause the malfunction. Most system complaints are linked to faulty wiring and connectors, and occasionally to components. Understanding the heater A/C-control and using the diagnostic tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.
Diagnostic Aids
The diagnostic aids include the history and current trouble codes and the related diagnostic tables.
| • | The following conditions may result in an intermittent operation of the heater-A/C control with no Diagnostic Trouble Codes (DTCs) stored: |
| - | Any condition which results in the interruption of power to the heater-A/C control |
| - | Out of range battery or ignition voltage specification. Normal battery or ignition voltage: 9V-16V |
| - | A loose or damaged ground(s) |
| - | An open or short in the Class 2 serial data link |
| • | An intermittent failure in the electronic system may be very difficult to detect and accurately diagnose. The heater-A/C control tests for different malfunctions under different vehicle conditions. A thorough test drive is often needed in order to repeat a fault condition. If the system malfunction is not repeated during the test drive, a good description of the complaint may be very useful in locating an intermittent fault condition. Faulty electrical connections or wiring cause most intermittent problems. When an intermittent condition is suspected, check the suspected circuits for the following conditions: |
| - | Poor mating of connector halves or backed out terminals |
| - | Improperly formed or damaged terminals |
| - | Wire chafing |
| - | Poor wire-to-terminal connections |
| - | Dirty wire-to-terminal connections |
| - | Dirty or corroded terminals |
| - | Damage to connector bodies |
| • | Use the J 35616 whenever a diagnostic procedure requests probing or checking a terminal. Using this adapter ensures that no damage to the terminal will occur and indicates whether the contact tension is sufficient. |
| • | Use the scan tool in order to read the DTCs set by the system. Refer to Scan Tool . If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving the related wiring and connectors. This often causes the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored. Refer to Intermittents and Poor Connections for more information. |
| • | Exit all of the scan tool tests before cycling the ignition switch from the off position to the on position unless you are directed otherwise. Follow the operating instructions in the scan tool user manual. Failure to follow these instructions may set DTCs, cause vehicle system malfunctions, set false DTCs, or cause scan tool malfunctions. |
| • | Inspect all relative fuses (see schematic) for the heater-A/C control. If the fuses are open, inspect the circuits which are fed power by these fuses for a short to ground. |
| • | Ensure that all relative grounds are clean and tight. |
| • | For heater-A/C control service procedures, refer to Control Assembly Replacement . |
| • | Inspect for a broken (or partially broken) wire inside of the insulation. A broken (or partially broken) wire may cause a system malfunction but prove good in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load). |
| • | Inspect for proper installation of the aftermarket electronic equipment. Improper installation may affect the integrity of other systems. |
Special Tools Required
The following special tools are required in order to complete the diagnostics:
- J 35616-200 Unpowered Test Light
- J 35616 Connector Test Adapter Kit
- J 39200 Digital Multimeter
- Scan Tool Tech2 Diagnostic Scan Tool
Function Check
- The following conditions indicate that the electrical circuits are functioning correctly:
- The heater-A/C control assembly (mode selector) is operating correctly when the designated outlets distribute air.
| • | The air conditioning blower motor operates at the appropriate speed with the control (mode) in any position except OFF. Verify that the compressor clutch also engages. |
| • | The blower motor will not operate in any speed with the control in the OFF position. |
Perform the following A/C Function Tests.
Preliminary Checks:
| • | Inspect for temperature change when the temperature knob position is changed. |
| On dual control systems, inspect the left side and the right side outlets when the temperature control position is changed. |
| • | Listen for a decrease in air noise, due to the closing of the recirculation valve, when going from MAX mode to A/C mode. |
| • | Inspect all of the IP outlets. Verify that the following conditions exist: |
| - | The barrel rotates. |
| - | The vane operates. |
| - | The barrel and vanes hold the present position in HI blower operation. |
HVAC System Check
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Is the heater-A/C control display on? | -- | Go to Step 2 | Go to Step 7 |
2 |
Does the blower motor turn on and change speed? | -- | Go to Step 3 | |
3 |
Does the A/C compressor turn on and off properly when using the A/C system? For more information. Refer to Powertrain Control Module Controlled Air Conditioning Description in Engine Controls - 3.5L or to Powertrain Control Module Controlled Air Conditioning Description in Engine Controls - 3.8L. | -- | Go to Step 4 | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis for the 3.5L engine or to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis for the 3.8L engine in Engine Controls |
4 | Test each of the air flow modes by selecting the individual modes with the MODE control on the heater-A/C control. Does the air flow move through the proper vents for each mode? | -- | Go to Step 5 | |
5 | Turn the driver temperature control from full cold to full hot. Does the driver air temperature control operate properly and is the air temperature display accurate? | Go to Step 6 | ||
6 |
Does the passenger air temperature control operate properly? | -- | Go to Step 8 | |
7 | Observe the radio display. Is the radio display also inoperative? | -- | Go To Interior Lights Dimming System Check in Lighting Systems | -- |
8 |
Has communication been established? | -- | Go to Step 9 | |
9 | Inspect for heater-A/C trouble codes. Are there any heater-A/C current or history trouble codes stored? | -- | Go to DTC Table | System OK |
