A/C Pressure Switch Circuit Troubleshooting

WARNING: This page is about a different car, the 2006 Acura MDX, 2005 Acura MDX, 2004 Acura MDX, and 2003 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Do not use this troubleshooting procedure if 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 doing symptom troubleshooting, check for powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ).

Disconnect the A/C pressure switch 4P connector.
Turn the ignition switch 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 No. 1 Terminal Of A/C Pressure Switch 4P Connector And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 4.
2. NO - Repair open in the wire between A/C diode A, the PCM, and the A/C pressure switch.
Turn the ignition switch OFF.
Check for continuity between the No. 1 and No. 4 terminals of the A/C pressure switch.

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

Is there continuity?
1. YES - Go to step 6.
2. NO - Go to step 12.
Reconnect the A/C pressure switch 4P connector.
Disconnect climate control unit connector B (26P).
Turn the ignition switch ON (II).
Measure the voltage between the No. 4 terminal of climate control unit connector B (26P) and body ground.

Fig 3: Measuring Voltage Between No. 4 Terminal Of Climate Control Unit Connector B (26P) And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 10.
2. NO - Repair the open in the wire between the climate control unit and the A/C pressure switch.
Turn the ignition switch OFF.
Measure the resistance between the No. 1 and No. 20 terminals of the climate control unit connector B (26P).

Fig 4: Measuring Resistance Between No. 1 And No. 20 Terminals Of Climate Control Unit Connector B
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is the resistance less than 24 kΩ ?
1. YES - Check for loose wire or poor connections at climate control unit connector B (26P) 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.
2. NO - Test the evaporator temperature sensor (see EVAPORATOR TEMPERATURE SENSOR TEST ).
Check for proper A/C system pressure.
Is the pressure within specifications?
1. YES - Replace the A/C pressure switch.
2. NO - Repair the A/C pressure problem.