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 blower control dial to ON: The A/C condenser fan, the radiator fan, or the A/C compressor. Refer to the symptom troubleshooting index.
Do not use this troubleshooting procedure if the A/C system pressure is abnormal.
Before doing symptom troubleshooting, check for PGM-FI DTCs.
1.
Blower motor operation check:

Blower motor operation check
?1.
Turn the vehicle to the ON mode.

?2.
Check that 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 threshold check:

A/C pressure threshold check
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Connect the HDS to the DLC.

?3.
Start the engine.

?4.
Set the A/C button and the blower control dial to ON.

?5.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
A/C PRESSURE SENSOR
196?2,850
kPa
    
2.00?29.07
kgf/cm2
28.4?413.3
psi

Do the current condition(s) match the threshold?

     
YES
     
     
     
Go to step 3.
     
NO
     
     
     
Go to the A/C system test.?
3.
HVAC control system check:

HVAC control system check
?1.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
A/C SWITCH
ON
      
A/C CLUTCH
ON
      

Do the current condition(s) match the threshold?

     
YES
     
     
     
     
NO
     
     
     
A/C SWITCH is OFF, go to step 4.
     
NO
     
     
     
A/C SWITCH is ON and A/C CLUTCH is OFF, update the PCM if it does not have the latest software, or substitute a known-good PCM, and recheck.?
4.
Determine possible failure area (ACS/TERMAL PRT line, others):

Determine possible failure area (ACS/TERMAL PRT line, others)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
HVAC control unit 32P connector

?3.
Turn the vehicle to the ON mode.

?4.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
HVAC control unit 32P connector: disconnected
Test point 1
HVAC control unit 32P connector No. 25
Test point 2
Body ground

Is there battery voltage?

     
YES
     
     
     
The ACS/TERMAL PRT wire is OK. Go to step 5.
     
NO
     
     
     
Go to step 6.
5.
HVAC control unit check:

HVAC control unit check
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Reconnect the HVAC control unit 32P connector.

?3.
Start the engine.

?4.
Set the A/C button and the blower control dial to ON.

?5.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
Test point 1
HVAC control unit 32P connector No. 25
Test point 2
Body ground

Is there 0.2 V or less?

     
YES
     
     
     
     
NO
     
     
     
Go to step 9.
6.
Open wire check (TERMAL PRT line):

Open wire check (TERMAL PRT line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
A/C compressor clutch 3P connector

?3.
Turn the vehicle to the ON mode.

?4.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
HVAC control unit 32P connector: disconnected
A/C compressor clutch 3P connector: disconnected
Test point 1
A/C compressor clutch 3P connector No. 2
Test point 2
Body ground


Is there battery voltage?

     
YES
     
     
     
TERMAL PRT wire is OK. Go to step 7.
     
NO
     
     
     
Go to step 8.
7.
A/C compressor thermal protector check:

A/C compressor thermal protector check
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Test the A/C compressor thermal protector.

Is the A/C compressor thermal protector OK?

     
YES
     
     
     
Repair an open in the wire between the HVAC control unit and the A/C compressor.?
     
NO
     
     
     
8.
MICU check:

MICU check
?1.
Measure the voltage between test points 1 and 2.
Test condition
Vehicle ON mode
HVAC control unit 32P connector: disconnected
A/C compressor clutch 3P connector: disconnected
Test point 1
Under-dash fuse/relay box connector D (32P) No. 31
Test point 2
Body ground


Is there battery voltage?

     
YES
     
     
     
Repair an open in the wire between the A/C compressor and the under-dash fuse/relay box.?
     
NO
     
     
     
9.
Evaporator temperature sensor check:

Evaporator temperature sensor check
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Measure the resistance between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
HVAC control unit 32P connector: disconnected
Test point 1
HVAC control unit 32P connector No. 19
Test point 2
HVAC control unit 32P connector No. 20

Is the resistance less than 24 k??

     
YES
     
     
     
     
NO