Inspection Procedure 4

INSPECTION PROCEDURE 4: Radiator Fan and Condenser Fan do not Change Speed or Stop

NOTE: If the engine coolant temperature reaches 110°C (230°F) or higher, the radiator fan control runs the radiator fan for up to 5 minutes even after the ignition switch is turned to the "LOCK" (OFF) position [the fan stops its rotation when the engine coolant temperature decreases to 110°C (230°F) or lower.

CIRCUIT OPERATION
^ The fan controller is powered from fusible link number 2.
^ The ECM [M/T] or PCM [A/T] judges the required revolution speed of radiator fan motor and condenser fan motor using the input signals transmitted from A/C switch, automatic compressor controller, vehicle speed sensor and engine coolant temperature sensor. The ECM [M/T] or PCM [A/T] activates the fan controller to drive the radiator fan motor and condenser fan motor.

TECHNICAL DESCRIPTION
^ The fan controller has variable control of the radiator fan motor and the condenser fan motor speeds using signals transmitted from the ECM [M/T] or PCM [A/T].

TROUBLESHOOTING HINTS
^ Malfunction of fan control relay
^ Malfunction of fan controller
^ Malfunction of ECM [M/T] or PCM [A/T]

DIAGNOSIS

Required Special Tool:
^ MB991223: Harness Set

STEP 1. Check the fan control relay.
Q: Is the fan control relay in good condition?
YES: Go to Step 2.
NO: Replace the part, then go to Step 6.

STEP 2. Check the harness wire between fan control relay connector A-09X (terminal 2) and fan controller connector A-17 (terminal 3).








Q: Are the harness wire between fan control relay connector A-09X (terminal 2) and fan controller connector A-17 (terminal 3) damaged?
YES: Repair or replace the part, then go to Step 6.
NO: Go to Step 3.

STEP 3. Measure the output circuit voltage at ECM connector C-121 [M/T] (terminal 21) or PCM connector C-120 [A/T] (terminal 18) by backprobing.








1) Do not disconnect ECM connector C-121 [M/T] or PCM connector C-120 [A/T].
2) Start the engine and run it at idle. [Engine coolant temperature: 80°C (176°F) or less]
3) Measure the voltage between terminal number 21 [M/T] or 18 [A/T] and ground by backprobing.
Q: Is the voltage 0 - 0.3 volt when the radiator fan is not operating?
YES: Go to Step 6.
NO: Go to Step 4.

STEP 4. Check the harness wire between ECM connector C-121 [M/T] or PCM connector C-120 [A/T] and fan controller connector A-17.





NOTE: If intermediate connector A-13 terminal 1 is damaged, repair or replace it.








Q: Are the harness wires between ECM connector C-121 [M/T] (terminal 21) or PCM connector C-120 [A/T] (terminal 18) and fan controller connector A-17 (terminal 2) damaged?
YES: Repair or replace them, then go to Step 6.
NO: Go to Step 5.

STEP 5. Check the fan controller at ECM connector C-121 [M/T] or PCM connector C-120 [A/T].








1) Disconnect ECM connector C-121 [M/T] or PCM connector C-120 [A/T].
2) Pull out the terminal number 21 [M/T] or 18 [A/T] and connect it to the body ground.
3) Reconnect ECM connector C-121 [M/T] or PCM connector C-120 [A/T] with pin 21 [M/T] or 18 [A/T] still removed.
4) Turn the ignition switch to the " ON" position.
Q: Do the radiator fan motor and condenser fan motor stop?
YES: Replace the ECM [M/T] or PCM [A/T]. Then go to Step 6.
NO: Replace the fan controller. Then go to Step 6.

STEP 6. Check the symptoms.
Q: Do the radiator fan and condenser fan operate correctly?
YES: The procedure is complete.
NO: Return to Step 1.