A/C Signal Circuit Troubleshooting (Manual A/C)

HVAC

A/C Signal Circuit Troubleshooting

A/C Signal Circuit Troubleshooting

NOTE:
* Do not use this troubleshooting procedure if any of the following items are operative with the A/C button and the fan control dial to ON: The A/C condenser fan, the radiator fan, or the A/C compressor. Refer to the symptom troubleshooting index.
* Before doing symptom troubleshooting, check for PGM-FI DTCs How To Troubleshoot The Fuel And Emissions Systems.
* Do not use this troubleshooting procedure if the A/C system pressure is abnormal.

1. Blower motor operation check:

Blower motor operation check
-1. Turn the ignition switch to ON (II).

-2. Check if the blower motor operates at all speeds.

Does the blower motor operate at all speeds?
-YES- Go to step 2.
-NO- Repair the problem in the blower motor circuit.

2. A/C pressure check:

A/C pressure check
-1. Turn the ignition switch to LOCK (0).

-2. Connect the HDS to the DLC.

-3. Start the engine.

-4. Set the A/C button and the fan control dial to ON.

-5. Using the HDS, confirm the following value in the PGM-FI Data List at idle.





Is the value within specifications?
-YES- Go to step 3.
-NO- Go to the A/C system test result. A/C System Test

3. HVAC control system check:

HVAC control system check
-1. Using the HDS, confirm the following values in the PGM-FI Data List at idle.





Are all the values within specifications?
-YES- Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM (K24Z7 engine) Service and Repair or ECM/PCM (except K24Z7 engine) and recheck.
-NO- A/C switch is OFF, go to step 4.
-NO- A/C switch is ON and A/C clutch is OFF, go to the A/C compressor clutch circuit troubleshooting A/C Compressor Clutch Circuit Troubleshooting (Manual A/C).

4. Open wire check (THERMAL _PRT line):

Open wire check (THERMAL _PRT line)
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Turn the ignition switch to ON (II).

-4. Measure the voltage between test points 1 and 2.









Is there battery voltage?
-YES- Go to step 7.
-NO- Go to step 5.

5. Open wire check (AC_P_SW line (K24Z7 engine) or A/C_PRESS_SW line (except K24Z7 engine)):

Open wire check (AC_P_SW line (K24Z7 engine) or A/C_PRESS_SW line (except K24Z7 engine))
-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.





-3. Turn the ignition switch to ON (II).

-4. Measure the voltage between test points 1 and 2.

















Is there battery voltage?
-YES- Go to step 6.
-NO- Repair an open in the wire between the A/C compressor and the under-dash fuse/relay box connector D (32P) terminal No. 14. If the wire is OK, replace the under-dash fuse/relay box.

6. Open wire check (THERMAL_PRT/THERMO lines):

Open wire check (THERMAL_PRT/THERMO lines)
-1. Check for continuity between test points 1 and 2.

















Is there continuity?
-YES- Test the A/C compressor thermal protector.
-NO- Repair an open in the wire between the HVAC control unit and the A/C compressor.

7. Evaporator temperature sensor check:

Evaporator temperature sensor check
-1. Turn the ignition switch to LOCK (0).

-2. Measure the resistance between test points 1 and 2.









Is resistance less than 24 kOhms?
-YES- Replace the HVAC control unit HVAC Control Unit Removal and Installation (With Navigation).
-NO- Test the evaporator temperature sensor Service and Repair.