GM Full-Size Trucks 1988-1998 Repair Information

Auxiliary Fan Switch

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OPERATION



The auxiliary fan circuit contains the auxiliary fan, coolant temperature sensor and a relay. When the sensor reaches a predetermined temperature, it closes the circuit to the relay. This energizes the relay sending 12 volts to the auxiliary fan. When the temperature decreases below the set point of the sensor, the circuit opens and the voltage is no longer applied to the auxiliary fan.

TESTING



  1. Check the condition of the fan switch and wiring. Repair as necessary.
  2.  
  3. Attach one end of a jumper wire to a good 12 volt power source and the other end of the jumper wire to the orange wire at the cooling fan relay.
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  5. The fan should operate. If the fan does operate the switch is probably defective.
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  7. If the fan does not operate, unplug the fan electrical harness and apply 12 volts directly to the fan. If the fan does not operate, the fan motor is probably defective. If the fan does operate, the relay could be defective.
  8.  

REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the sensor electrical lead and unscrew the sensor. The sensor can be found on the right side of the engine.
  4.  

To install:
  1. Install the sensor or relay and connect the electrical lead.
  2.  
  3. Connect the battery cable.
  4.  

 
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