Tuesday, September 23, 2008

Honda Civic a/c will not work

Honda Civic a/c will not work

VEHICLE: 2002 Honda Civic LX 1.7L, L4, MFI, SOHC, VIN -, Eng Desg D17A1, Eng Version N/R, 1700 CC

MILEAGE: 113000

Customer Concern: The A/C compressor will not operate. Also, the scan tool does not indicate that there is any A/C request.


1. Locate the A/C pressure switch on the high side A/C line by the alternator. The wire colors are Red (RED) and Blue (BLU). With the pressure switch unplugged, the RED wire should have 10 to 12 volts reference voltage on a voltmeter. When the reference voltage is grounded, the Multiplex Control Unit (MCU) will see an A/C request and send that request to the Engine Control Module (ECM).

2. If there is no voltage to the A/C pressure switch, unplug the A/C Compressor 3-terminal connector, check the Blue/White (BLU/WHT) wire on the harness side of the connector, and look for voltage. If there is voltage, then backprobe the BLU/WHT wire, plug in the connector and start the vehicle. Then ground the BLU/WHT wire and verify that the A/C compressor and condenser fan operate.

3. Test the A/C Thermal Protector. The voltage on the BLU/WHT wire should go through the A/C Thermal Protector and then to the A/C Pressure switch RED wire. Check to see if the A/C Thermal Protector is open or if there is a wire harness problem between the A/C Thermal Protector and the pressure switch.

4. Always verify that there are no codes in the climate control system. If there is a problem, the climate control may not ground the A/C request circuit.

Potential Causes:


Heater Ventilation Air Conditioner (HVAC) Thermal Protector

Confirmed Fix:

Replaced Auxiliary Heater Ventilation Air Conditioner (HVAC) Control Module

Replaced Heater Ventilation Air Conditioner (HVAC) Thermal Protector

Tech Tips: The heater control panel was not grounding the Blue wire.

Never jump voltage to the A/C request circuit when testing out the A/C system.

Spark plug wires
Exhaust and convertors
K&n oil and air filters
Oxygen or o2 sensor
Step by step instructions on how to change your own spark plugs and wires
Keep your engine properly tuned


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