Montero 4WD V6-2972cc 3.0L SOHC (1991)
A/C Signal: Testing and Inspection
Air Conditioning Circuit
To test the A/C signal, proceed as follows.
1. Start and warm the engine to operating temperature. Turn the blower and A/C to the ON position.
2. Using a volt meter, check the voltage between ECU harness terminal 7 and ground.
Voltage
System voltage.
NOTE: If voltage does not exist and the harness tests O.K. (step #4), check the A/C system for faults.
3. Turn the key to the OFF position and disconnect the negative battery terminal and ECU connector.
4. Using an ohm meter, check for continuity between ECU harness terminal 7 and harness terminal 2 of the engine coolant temperature switch.
Continuity
Should exist.
5. Using an ohm meter, check for continuity between engine coolant temperature switch terminal 1 and A/C dual pressure switch harness terminal 2.
Continuity
Should exist.
6. Using an ohm meter check for continuity between ECU harness terminal 7 and ground.
Continuity
Should not exist.
NOTE: If the engine temperature is above approximately 235° F, the coolant temperature switch will open the circuit between the A/C control unit
and the ECU.
If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed,
confirm that the repair has corrected the problem.