A/C Pressure Switch Circuit Troubleshooting

NOTE:

Do not use this troubleshooting procedure if any of the following items are operative; A/C condenser fan, radiator fan, A/C compressor, or if the heater is inoperative. Refer to the symptom troubleshooting index.
Before performing symptom troubleshooting, check for powertrain DTCs: '00-05 models (see GENERAL TROUBLESHOOTING INFORMATION ); '06-09 models (see GENERAL TROUBLESHOOTING INFORMATION ).

Disconnect the A/C pressure switch 2P connector.
Turn the ignition switch to ON (II).
Measure the voltage between A/C pressure switch 2P connector terminal No. 2 and body ground.

Fig 1: Measuring Voltage Between A/C Pressure Switch 2P Connector Terminal No. 2 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V?

YES -Go to step 4.

NO -Go to step 15.
Turn the ignition switch to LOCK (0).
Check for continuity between A/C pressure switch terminals No. 1 and No. 2.

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

Is there continuity?

YES -Go to step 6.

NO -Go to step 17.
Reconnect the A/C pressure switch 2P connector.
Disconnect the HVAC control unit 30P connector.
Turn the ignition switch to ON (II).
Measure the voltage between HVAC control unit 30P connector terminal No. 12 and body ground.

Fig 3: Measuring Voltage Between HVAC Control Unit 30P Connector Terminal No. 12 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V?

YES -Go to step 10.

NO -Repair open in the wire between the HVAC control unit and the A/C pressure switch.
Turn the ignition switch to LOCK (0).
Measure the resistance between HVAC control unit 30P connector terminals No. 7 and No. 10.

Fig 4: Measuring Resistance Between HVAC Control Unit 30P Connector Terminals No. 7 And No. 10
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is the resistance less than 24 k Ω?

YES -Go to step 12.

NO -Repair cause of high resistance in the evaporator temperature circuit.
Reconnect the HVAC control unit 30P connector.
Turn the ignition switch to ON (II).
Check the blower motor operation at several speeds.
Does the blower motor operate at all speeds?

YES -Check for loose wires or poor connections at the HVAC control unit 30P connector, and at the A/C pressure switch 2P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit.

NO -Repair the problem in the blower motor circuit.
Make sure the A/C switch is OFF.
Using a backprobe set, measure the voltage between ECM connector A (32P) terminal No. 27 and body ground with the ECM connectors connected ('00-05 models) or between ECM connector E (31P) terminal No. 28 and body ground with the ECM connectors connected ('06-09 models).
'00-05 models

Fig 5: Measuring Voltage Between ECM Connector A (32P) Terminal No. 27 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

'06-09 models

Fig 6: Measuring Voltage Between ECM Connector E (31P) Terminal No. 28 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V?

YES -Repair open in the wire between the ECM and the A/C pressure switch.

NO -Check for loose wires or poor connections at ECM connector A (32P) ('00-05 models), or ECM connector E (31P) ('06-09 models). If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM: '00-05 models (see ECM REPLACEMENT ); '06-09 models (see ECM REPLACEMENT ).
Check for proper A/C system pressure.
Is the pressure within specifications?

YES -Replace the A/C pressure switch (see A/C LINE REPLACEMENT ).

NO -Repair the A/C pressure problem.