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 ignition switch to ON (II).

?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 ignition switch to LOCK (0).

?2.
Connect the HDS to the DLC.

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

?4.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
A/C PRESSURE SENSOR
196?3,138
kPa
    
2.00?32.00
kgf/cm2
28.4?455.1
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.
Start the engine.

?2.
Set the A/C button and the blower control dial to ON.

?3.
Using the HDS, confirm the following values in the PGM-FI Data List at idle.
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. Check the ECT, idle speed and throttle position values, if in specification, continue; if not troubleshoot ECT sensor, idle speed and throttle position; update the PCM if it does not have the latest software, or substitute a known-good PCM, and recheck.?
4.
ACS line voltage check:

ACS line voltage check
?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.
Test condition
IG ON (II)
HVAC control unit 32P connector: disconnected
Test circuit
ACS
Test point 1
HVAC control unit 32P connector No. 27 (RED)
Test point 2
Body ground


Is there 10 volts or more?

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

HVAC control unit check
?1.
Turn the ignition switch to LOCK (0).

?2.
Reconnect 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
IG ON (II)
Test circuit
ACS
Test point 1
HVAC control unit 32P connector No. 27 (RED)
Test point 2
Body ground


Is there 0.2 V or less?

     
YES
     
     
     
     
NO
     
     
     
Go to step 7.
6.
Open wire check (ACS line):

Open wire check (ACS line)
?1.
Turn the ignition switch to LOCK (0).

?2.
Disconnect the following connector.

?3.
Check for continuity between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Under-dash fuse/relay box connector K (4P): disconnected
Test circuit
ACS
Test point 1
HVAC control unit 32P connector No. 27 (RED)
Test point 2
Under-dash fuse/relay box connector K (4P) No. 1 (RED)


Is there continuity?

     
YES
     
     
     
     
NO
     
     
     
Repair an open in the wire between the HVAC control unit and the under-dash fuse/relay box.?
7.
Evaporator temperature sensor check:

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

?2.
Disconnect the following connectors.

?3.
Measure the resistance between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Test circuit
TEVA, SENSOR COM
Test point 1
HVAC control unit 32P connector No. 20 (BLU)
Test point 2
HVAC control unit 32P connector No. 32 (RED)


Is the resistance less than 24 k??

     
YES
     
     
     
     
NO