GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

Engine Fan

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CAUTION
An electric fan under the hood can start up even when the engine is not running and can injure you. Keep hands, clothing and tools away from any underhood electric fan.

Early models use one large cooling fan with five blades to aid airflow through the radiator/condenser. They are driven by an electric motor mounted to the radiator support. The ECM and a relay activate the fan motor. If the vehicle is equipped with A/C, a second switch can activate the circuit, depending upon A/C compressor head pressure to the condenser.

Later models use two cooling fans; a main cooling fan, and auxiliary fan to aid airflow through the condenser. A coolant temperature switch activates the fans. A transducer can also activate the circuit, depending upon A/C compressor head pressure to the condenser.

See Figures 1 and 2



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Fig. Fig. 1: Exploded view of dual electric cooling fans; The main and auxiliary fans



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Fig. Fig. 2: Side by side electric fan mounting

Removal & Installation



Single or Main Fan
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and duct assembly.
  4.  
  5. Disconnect the wiring harness from the fan motor.
  6.  

See Figure 3

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Fig. Fig. 3: Unplug the fan electrical connector

  1. Remove the fan mounting bolts.
  2.  

See Figure 4

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Fig. Fig. 4: Removing the upper fan mounting bolt

  1. Remove the fan assembly.
  2.  

See Figure 5

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Fig. Fig. 5: Pulling the engine cooling fan out the top

  1. Installation is the reverse of the removal procedure.
  2.  

Auxiliary Fan
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the upper fan mounting bolt.
  4.  

See Figures 6 and 7

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Fig. Fig. 6: View of the upper mounting bolt for the condenser fan



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Fig. Fig. 7: Remove the fan upper mounting bolts

  1. Raise and suitably support the vehicle.
  2.  
  3. Remove the lower air baffle. This may also be called a deflector, or splash shield and may be secured with screws, bolts or retaining clips.
  4.  

See Figures 8, 9 and 10

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Fig. Fig. 8: Exploded view of the radiator lower air deflector



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Fig. Fig. 9: Insert a small flat-bladed tool, into the slot to release the tab on the lower splash shield ...



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Fig. Fig. 10: ... then lower the front splash shield for access to the fan retainers

  1. Disconnect the wiring harness to fan motor.
  2.  
  3. Remove the lower mounting bolts and/or nuts, then remove the auxiliary (condenser) fan.
  4.  

See Figures 11 through 16

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Fig. Fig. 11: Remove the lower fan mounting bolt(s)



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Fig. Fig. 12: Use of a long extension makes reaching ...



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Fig. Fig. 13: ... this lower retaining nut much easier



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Fig. Fig. 14: There is more room than appears to access this fan lower mounting



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Fig. Fig. 15: Remove the retaining nut ...



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Fig. Fig. 16: ... then slide the condenser fan off the stud, down, and out of the vehicle.

To install:
  1. Install the auxiliary fan and tighten the mounting bolts to 89 inch lbs. (10 Nm)
  2.  
  3. Connect the wiring harness to the fan motor.
  4.  
  5. Install the lower air baffle.
  6.  
  7. Lower the vehicle and install the upper mounting bolt.
  8.  
  9. Connect the negative battery cable.
  10.  

TESTING



Electric cooling fans operate when engine coolant temperature exceeds a certain value, or the A/C is engaged. The PCM completes the ground paths for the windings of the cooling fan relays. The relay contacts then close and complete the circuit between the fusible link and the fan motor. When the engine cools down, or the A/C is turned off. The PCM removes the ground for the fan relays and the fans stop.

Diagnosis of the system is done through the PCM and the use of a scan tool. It is possible to check the basic condition of the circuits and components to determine their condition.

An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect the hard-shell connectors for backed out terminals. Check for improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

If connections and harness check OK, connect a digital voltmeter from the affected terminal to ground while moving related connectors and harnesses; if the failure is induced, the voltage reading will change.

3.1L Engine

The electric cooling fan is controlled by the PCM, based on inputs from the ECT sensor, A/C request, and the A/C refrigerant fan request switch and vehicle speed. The PCM controls the fans by grounding the circuits that energize the fan control relays. Battery voltage is then supplied to the fan motors.

The PCM grounds the circuit for the cooling fan (puller fan relay terminal -86'), when coolant temperature is approximately 106°C (223°F); or when A/C has been requested, and the A/C refrigerant fan request switch opens with high A/C pressure, about 200 psi (1380 kPa).

The pusher fan relay is grounded by the PCM when coolant temperature is approximately 110°C (217°F), and/or the puller fan is "ON" for A/C pressure.

See Figures 17 and 18

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Fig. Fig. 17: Coolant fan control circuit diagnosis-3.1L engine



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Fig. Fig. 18: Coolant Fan Control Circuit Schematic-3.1L engine

The numbers used below refer to the circled numbers on the accompanying diagnostic flow chart.

  1. 12 volts should be available to both terminals -87' and -85', when the ignition is "ON".
  2.  
  3. This test checks the ability of the PCM to ground circuit 335 and circuit 473. The MIL (Service Engine Soon) should also be flashing at this point.
  4.  
  5. This test checks to see if the coolant puller and pusher fan relay (circuits 409 and 532) are open. Jumping terminals '87' and -30' bypasses the relay, which should cause the fans to run, if the fan motors and wiring are OK.
  6.  

If the engine is overheating and the cooling fan is ON, the cooling system should be checked.

3.4L Engine

Power for the fan motors is supplied through two Maxifuses® in the underhood electrical center. The cooling fan relays are energized when current flows from the two Maxifuses® through the relay coils to ground through the PCM. The coolant Fan #1 Relay (Cool Fan 1 Relay) control circuit is grounded for low speed fans operation. The Coolant Fan #1 Relay control circuit and the Coolant Fan 2 Relay control circuit (Cool Fan Relay and Cool Fan 2 Relay) are grounded for high-speed fans operation.

During low speed fan operation, the PCM supplies a ground path for Cool Fan 1 Relay. This closes the Cool

Fan 1 Relay contacts, allowing current to flow from the U/H Electrical center through the relay contacts to the left engine-cooling fan. During low speed operation, the ground path for the primary cooling fan is through the engine Cool Fan Relay and the right engine cooling fan motor. The result is a series circuit with both cooling fans running at low speed.See Figure 19

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Fig. Fig. 19: Cooling fan circuit diagram-3.4L engine

During high speed cooling fan operation, the PCM supplies a ground path for the Cool Fan 1 Relay. The PCM also supplies a ground path for Cool Fan cooling fan relays. During high speed fans operation, both the right and the left engine cooling fans are supplied current from the U/H Electrical Center and each cooling fan has its own ground path.

Testing of this system is done with a scan tool. Stored diagnostic codes may affect engine cooling fans operation. Stored codes should be remedied before attempting to diagnose a cooling fan fault.

3.8L Engine

The PCM will complete the ground path for the winding of the puller fan (Fan 1) relay when it sees engine temperature above approximately 100°C (212°F) or when the A/C is requested. It turns the fan on by grounding the system through circuit -86' (the terminal number on the relay). The fans will continue to run for approximately 45 seconds after the A/C request is gone.

The cooling fans can be tested for proper operation.

Power for the fan motors comes from fusible links to terminal -87' on the relays. The relays are energized when current flows to ground through the PCM quad-driver #4.

  1. Turn the ignition key to the ON position, but do not start the engine.
  2.  
  3. Disconnect the puller fan relay and probe the harness connector cavities -85' and '87' with a test light connected to ground. The test light should light.
  4.  

See Figure 20

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Fig. Fig. 20: Cooling fan circuit diagram-3.8L engine

  1. If the test light does not light, trace and repair the open in the affected circuit.
  2.  
  3. If test light lights, jump the puller fan relay harness connector terminals '87' to -30'. The fan should run.
  4.  
  5. If the fan does not run, with jumper still connected, probe terminal "B" at the fan motor connector with a test light. The light should light.
  6.  
  7. If the light does not light, trace and repair the wire fault between the relay and the fan motor connector.
  8.  
  9. If test light lights, connect a test light between terminal "A" and "B" at the fan connector harness. The test light should light.
  10.  
  11. If the light does not light, repair wire fault in ground circuit to fan motor.
  12.  
  13. If test light lights, check for a loose connection at the fan; then check the fan operation.
  14.  
  15. Unplug the fan electrical connector.
  16.  
  17. Fabricate a jumper wire (using 10-gauge wire) and attach one end to terminal "A" on the fan motor.
  18.  
  19. Attach the other end to a good engine ground.
  20.  

  1. Now take the loose end and touch it to the positive battery terminal. The fan should spin; if it does not, replace it. Plug the fan connector in again.
  2.  

Puller fan (Fan #1) relay - The PCM energizes the relay through terminal -WD11' when engine coolant temperature reaches a set value or when the A/C is requested.

  1. Jump the puller fan relay harness connector terminals '87' to -30'. Fan should run.
  2.  
  3. Using a suitable Scan tool, turn Fan 1 "on". Probe the fan relay harness connector terminal -86' with a test light connected to battery power. Test light should light.
  4.  
  5. If the light does not light, trace and repair wire fault between the relay and the PCM, if connections and wiring are good; replace the PCM.
  6.  
  7. If the test light lights, replace the fan relay.
  8.  

Pusher fan (Fan #2) - The pusher fan relay is energized by the PCM if the A/C head pressure switch opens, indicating refrigerant pressure above 210 psi (1448 kPa), or when engine coolant temperature reaches 226°F (108°C). This fan is tested the same way.

 
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