A/C Pressure Switch Circuit Troubleshooting

NOTE:

Do not use this troubleshooting procedure if any of the following items are operative; the condenser fan, the radiator fan, the A/C compressor, or if the heater is inoperative. Refer to SYMPTOM TROUBLESHOOTING INDEX .
Check the A/C high-side pressure.
Before doing any symptom troubleshooting, check for powertrain DTCs (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.
Is there battery voltage?

YES - Go to step 4.

NO - Go to step 20.

Fig 1: Measuring Voltage Between A/C Pressure Switch 2P Connector Terminal No. 2 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch to LOCK (0).
Check for continuity between A/C pressure switch terminals No. 1 and No. 2.
Is there continuity?

YES - Go to step 6.

NO - Replace the A/C pressure switch.

Fig 2: Checking Continuity Between A/C Pressure Switch Terminals No. 1 & No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Reconnect the A/C pressure switch 2P connector.
Disconnect the A/C switch 5P connector.
Turn the ignition switch to ON (II).
Measure the voltage between A/C switch 5P connector terminal No. 2 and body ground.
Is there battery voltage?

YES - Go to step 10.

NO - Repair open in the wire between the A/C pressure switch and the A/C switch.

Fig 3: Measuring Voltage Between A/C Switch 5P Connector Terminal No. 2 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch to LOCK (0).
Test the A/C switch (see A/C SWITCH REPLACEMENT ).
Is the A/C switch OK?

YES - Go to step 12.

NO - Replace the A/C switch (see A/C SWITCH REPLACEMENT ).
Disconnect the heater fan switch 8P connector.
Check for continuity between A/C switch 5P connector terminal No. 1 and heater fan switch 8P connector terminal No. 6.
Is there continuity?

YES - Go to step 14.

NO - Repair open in the wire between the A/C switch and the heater fan switch.

Fig 4: Checking Continuity Between A/C Switch 5P Connector Terminal No. 1 & Heater Fan Switch 8P Connector Terminal No. 6
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Test the heater fan switch (see HEATER FAN SWITCH TEST ).
Is the heater fan switch OK?

YES - Go to step 15.

NO - Replace the heater fan switch (see HEATER CONTROL PANEL DISASSEMBLY AND REASSEMBLY ).
Remove the evaporator temperature sensor (see EVAPORATOR CORE REPLACEMENT ) and test it (see EVAPORATOR CORE REPLACEMENT ).
Is the evaporator temperature sensor OK?

YES - Go to step 16.

NO - Replace the evaporator temperature sensor (see EVAPORATOR CORE REPLACEMENT ).
Jump the SCS line with the HDS.
NOTE: This step must be done to protect engine/powertrain control module (ECM/PCM) from damage.
Disconnect ECM/PCM connector A (49P).
Check for continuity between the following terminals of ECM/PCM connector A (49P) and the evaporator temperature sensor 2P connector.
49P: 2P:

No. 10 No. 2

No. 38 No. 1

Fig 5: Checking Continuity Between Terminals Of ECM/PCM Connector A (49P) And Evaporator Temperature Sensor 2P Connector
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES - Go to step 19.

NO - Repair open in the wire(s) between the ECM/PCM and the evaporator temperature sensor.
Check for continuity between ECM/PCM connector A (49P) terminal No. 38 and body ground.
Is there continuity?

YES - Repair short to body ground in the wire between the ECM/PCM and the evaporator temperature sensor.

NO - Check for loose wires or poor connections at ECM/PCM connector A (49P), the evaporator temperature sensor 2P connector, the A/C pressure switch 2P connector, the A/C switch 5P connector, and at the heater fan switch 8P connector. If the connections are good, substitute a known-good ECM/PCM, and recheck. If the symptom/indication goes away, replace the original ECM/PCM.

Fig 6: Checking Continuity Between ECM/PCM Connector A (49P) Terminal No. 38 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch to LOCK (0).
Reconnect the A/C pressure switch 2P connector.
Disconnect the A/C compressor clutch 3P connector.
Turn the ignition switch to ON (II).
Measure the voltage between A/C compressor clutch 3P connector terminal No. 3 and body ground.
Is there battery voltage?

YES - Go to step 25.

NO - Go to step 27.

Fig 7: Measuring Voltage Between A/C Compressor Clutch 3P Connector Terminal No. 3 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch to LOCK (0).
Test the A/C compressor thermal protector (see A/C COMPRESSOR CLUTCH CHECK ).
Is the A/C compressor thermal protector OK?

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

NO - Replace the A/C compressor thermal protector (see A/C COMPRESSOR THERMAL PROTECTOR REPLACEMENT ).
Turn the ignition switch to LOCK (0).
Reconnect the A/C pressure switch 3P connector.
Make sure the A/C switch is OFF.
Turn the ignition switch to ON (II).
Measure the voltage between under-dash fuse/relay box connector A (36P) terminal No. 21 and body ground with the under-dash fuse/relay box connectors connected.
Is there battery voltage?

YES - Repair open in the wire between the A/C compressor and the MICU.

NO - Check for loose wires or poor connections at the under-dash fuse/relay box. If the connections are OK, substitute a known-good MICU and recheck. If the symptom goes away, replace the original MICU.

Fig 8: Measuring Voltage Between Under-Dash Fuse/Relay Box Connector A (36P) Terminal No. 21 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.