A/C Pressure Switch Circuit Troubleshooting

WARNING: This page is about a different car, the 2008 Acura TL and 2007 Acura TL. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

If the blower motor does not run at all speeds, the A/C compressor will be inoperative, before doing this troubleshooting, check the DTC and repair the cause of the inoperative blower motor.
Do not use this troubleshooting procedure if any of the following items are operative; A/C condenser fan, radiator fan, A/C compressor. Refer to the SYMPTOM TROUBLESHOOTING INDEX .
Before doing symptom troubleshooting, check for power train DTCs (see GENERAL TROUBLESHOOTING INFORMATION ).

Check for body DTCs using B-CAN system diagnosis test mode A troubleshooting (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).
Are there any DTCs indicated?

YES -Do the appropriate troubleshooting for the DTC indicated.

NO -Go to step 2.
Disconnect the A/C pressure switch 4P connector.
Turn the ignition switch to ON (II).
Measure the voltage between the No. 1 terminal of the A/C pressure switch 4P connector and body ground.

Fig 1: Measuring Voltage Between A/C Pressure Switch Connector Terminals No. 1 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there 5 V or more?

YES -Go to step 5.

NO -Repair open in the wire between the relay control module and the A/C pressure switch.
Turn the ignition switch to LOCK (0).
Check for continuity between the No. 1 and No. 4 terminals of the A/C pressure switch.

Fig 2: Checking Continuity Between No. 1 And No. 4 Terminals Of A/C Pressure Switch
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 7.

NO -Go to step 16.
Reconnect the A/C pressure switch 4P connector.
Disconnect climate control unit connector A (20P).
Turn the ignition switch to ON (II).
Measure the voltage between the No. 14 terminal of climate control unit connector A (20P) and body ground.

Fig 3: Measuring Voltage Between Climate Control Unit Connector Terminals No. 14 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

is there 5 V or more?

YES -Go to step 11.

NO -Repair open in the wire between the climate control unit and the A/C pressure switch.
Turn the ignition switch to LOCK (0).
Measure the evaporator temperature sensor resistance between the No. 5 and No. 18 terminals of climate control unit connector A (20P).

Fig 4: Measuring Evaporator Temperature Sensor Resistance Between No. 5 And No. 18 Terminals Of Climate Control Unit Connector A (20P)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is the resistance less than 24 kΩ?

YES -Go to step 13.

NO -Repair cause of high resistance in the evaporator temperature circuit.
Reconnect climate control unit connector A (20P).
Turn the ignition switch to ON (II).
Check that blower motor operates at all speeds.
Does the blower motor operate at all speeds?

YES -Check for loose wires or poor connections at climate control unit connector A (20P) and at the A/C pressure switch 4P connector. If the connections are good, substitute a known-good climate control unit and recheck. If the symptom/ indication goes away, replace the original climate control unit.

NO -Repair the problem in the blower motor circuit.
Check for proper A/C system pressure.
Is the pressure within specifications?

YES -Replace the A/C pressure switch.

NO -Repair the A/C pressure problem.