Chevrolet Trax: Air conditioning compressor malfunction
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The A/C compressor uses a conventional belt driven magnetic clutch to engage and mechanically turn the compressor. When the A/C switch is pressed, the HVAC control module sends an A/C request message to the ECM via serial data. If specific criteria is met, the ECM then grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the permanently grounded A/C compressor clutch. The A/C compressor clutch will then be activated.
Diagnostic Aids
The following conditions must be met in order to turn on the A/C compressor:
- Battery voltage is between 9-18 V.
- Engine coolant temperature is less than 124ºC (255ºF).
- Engine speed is greater than 600 RPM.
- Engine speed is less than 5 500 RPM.
- A/C high side pressure is between 269-2 929 kPa (39-425 PSI).
- Throttle position is less than 100%.
- Evaporator temperature is greater than 3ºC (38ºF).
- ECM does not detect excessive torque load.
- ECM does not detect insufficient idle quality.
- The ambient temperature is above 1ºC (34ºF).
- Blower motor ON
Reference Information
Schematic Reference
HVAC Schematics (Encore)
Connector End View Reference
WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX
Description and Operation
Automatic HVAC Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
NOTE: Refer to HVAC System Malfunction before performing this procedure.
- Ignition ON, press and release the A/C Switch.
- Verify the HVAC control module scan tool A/C Switch parameter changes between Active and Inactive.
If the parameter does not change
Replace the A26 HVAC Controls.
If the parameter changes
- Set A/C system to coolest setting with blower ON.
- Press and release the A/C switch several times.
- Verify the engine control module (ECM) scan tool A/C Request Signal parameter changes between Active and Inactive.
If the parameter does not change
Replace the K33 HVAC Control Module.
If the parameter changes
- Verify the A/C compressor clutch engages when commanding the engine control module (ECM) A/C Relay output function On and Off with a scan tool.
If the A/C compressor clutch does not engage
Refer to DTC P0645, P0646, or P0647
If the A/C compressor clutch engages
- All OK.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- HVAC Component Replacement Reference
- Control Module References for HVAC control module replacement, programming and setup
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Actuator recalibration
HVAC Control Module Replacement
When replacing or disconnecting the HVAC control module, it will be necessary
to perform a recalibration
process. When installing or reconnecting the HVAC control modu
Heater and air conditioning control replacement
Fig. 6: Heater And Air Conditioning Control
Heater and Air Conditioning Control Replacement
HEATER AND AIR CONDITIONING REMOTE CONTROL REPLACEMENT
Fig. 7: Heater And Air Conditioning Remote Cont
SEE MORE:
Oil pump
NOTE:
Examples used in this article are general in nature and do not necessarily
relate
to a specific engine or system. Illustrations and procedures have been chosen
to guide mechanic through engine overhaul process. Descriptions of processes
of cleaning, inspection, assembly and machine shop pract
Data communications - Description and operation
BODY CONTROL SYSTEM DESCRIPTION AND OPERATION
The body control system consists of the body control module (BCM),
communications, and various input and
outputs. Some inputs, outputs and messages require other modules to interact
with the BCM. The BCM also has
discrete input and output terminals to
