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

Electric Fan Switch



The Powertrain control module (PCM) controls the operation of the cooling fans. This is accomplished by providing a ground path for the cooling fan relay coils within the PCM. The relay contacts will close and complete the circuit between the Maxifuse® in the underhood electrical center and the fan motors. Whenever there is a fan "on" request, both fans will be running. A coolant temperature switch activates the fan motors. A transducer can also activate the circuit, depending upon A/C request or A/C compressor head pressure to the condenser.

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Wiring Schematic of cooling fans, relays, and ground.


For electric cooling fan testing procedures, please refer to Engine and Engine Overhaul of this repair guide.

Removal & Installation

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

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

See Figures 2 and 3

Click image to see an enlarged view

Fig. Fig. 2: Troubleshooting Basic Starting System Problems

Click image to see an enlarged view

Fig. Fig. 3: Troubleshooting Basic Charging System Problems