Checking the Engine Cooling Fan

Checking The Engine Cooling Fan





Condition
- Diagnostic trouble codes (DTCs) absent.
- Fault is permanent.

Possible source(s)
Constant half speed:
- Short-circuit to ground in low-speed signal cable
- Detective engine cooling fan (FC) relay.

Constant high-speed:
- Short-circuit to ground in high-speed signal cable.
- Defective engine cooling fan relay.

No low-speed:
- Detective engine cooling fan relay or engine cooling fan.

No high-speed:
- Open-circuit in high-speed signal cable
- Defective engine cooling fan relay or engine cooling fan.

Neither low-speed not high-speed:
- Open-circuit in power cable or ground lead.
- Defective engine cooling fan relay or engine cooling fan.





Check Engine Cooling Fan Speed
- Ignition off.

- If the engine cooling fan operates at low-speed even when the ignition is off: Select Alternative 1.

- If the engine cooling fan operates at high-speed even when the ignition is off: Select Alternative 2.

- If neither of the above symptoms appears: Select Alternative 3.

- Select a suitable alternative.

Alternative 1:
^ Proceed to Checking The Fan Control Relay, Half Speed section below.

Alternative 2:
^ Proceed to Checking Engine Cooling Tan Relay, High-speed section below.

Alternative 3:
^ Proceed to test step below.





Checking The Engine Cooling Fan
- Activate the engine cooling fan (FC).
- The cooling fan should operate at low-speed and high-speed.
- If the engine cooling fan does work at both speeds: Select Alternative 1.
- If the engine cooling fan only works at low- speed: Select Alternative 2.
- If the engine cooling fan only works at high- speed: Select Alternative 3.
- If the engine cooling fan does not work at all: Select Alternative 4.
- Select a suitable alternative.

Alternative 1:
^ The fault is intermittent.

Alternative 2:
^ Proceed to test step below.

Alternative 3:
^ Proceed to Checking The Fan Motor, Low-speed Side section below.

Alternative 4:
^ Proceed to Checking Ground Lead section below.





Checking Signal Cable, High-speed
- Connect the test box and check ground terminals.
- Disconnect connector B from the engine cooling fan relay.
- Connect an ohmmeter between coupling B connector 2 and #22 (# A22) on the test box.
- The ohmmeter should read approx. 0 ohms.

If reading is OK:
^ Proceed to test step below.

If reading is incorrect:
^ Check cable between engine cooling fan relay terminal B2 and engine control module (ECM) # A22 for an open-circuit.





Checking The Engine Cooling Fan Motor, High-speed
- Ignition off.
- Disconnect connector C from the engine cooling fan relay.
- Connect an ohmmeter between connector C terminal 2 and ground.
- The ohmmeter should read 0 - 10 ohms.

If reading is OK:
^ Try a new engine cooling fan relay.

If reading is incorrect:
^ Try a new engine cooling fan.





Checking The Fan Motor, Low-speed Side
- Ignition off.
- Disconnect connector C from the engine cooling fan relay.
- Connect an ohmmeter between connector C terminal 1 and ground.
- The ohmmeter should read 0 - 10 ohms.

If reading is OK:
^ Try a new engine cooling fan relay.

If reading is incorrect:
^ Try a new engine cooling fan.





Checking Ground Lead
- Ignition off.
- Disconnect the lead single-pin ground lead connector (C/EA).
- Connect an ohmmeter between the single-pin connector (bodywork side) and ground.
- The ohmmeter should read approx. 0 ohms.

If reading is OK:
^ Proceed to test step below..

If reading is incorrect:
^ Check ground terminal for contact resistance and oxidation and the cable between the engine cooling fan motor and ground for an open-circuit.





Checking The Engine Cooling Fan Motor
- Ignition off.
- Connect the single-pin ground lead connector.
- Disconnect connector C from the engine cooling fan relay.
- Connect an ohmmeter between connector C terminal 2 and ground.
- The ohmmeter should read 0 - 10 ohms.

If reading is OK:
^ Try a new engine cooling fan relay.

If reading is incorrect:
^ Try a new engine cooling fan.





Checking The Fan Control Relay, Half Speed
- Ignition off.
- Disconnect connector B from the engine cooling fan relay.
- Does the engine cooling fan cut out?

Yes:
^ Check cable between engine cooling fan relay terminal B1 and engine control module # A7 for a short-circuit to ground.

No:
^ Try a new engine cooling fan relay.





Checking Engine Cooling Tan Relay, High-speed
- Ignition off.
- Disconnect connector B from the engine cooling fan relay.
- Does the engine cooling fan cut out?

Yes:
^ Check cable between engine cooling fan relay terminal B2 and engine control module # A22 for a short-circuit to ground.

No:
^ Try a new engine cooling fan relay.