How to Change Cooling-Fan Switch in Your Vehicle

The vehicles that are outfitted with cooling fans have switches that sense the temperature of the antifreeze (coolant) and turn on the fan according to the predetermined temperature level. In other case the antifreeze will boil and overheat the engine.

To test whether the switch is responsible for overheating or not is not a big task. You can easily test it with the help of ohmmeter.

Steps to Follow

  • Make sure that the engine is cool. Open the engine hood and start the engine to locate whether the cause of overheating is failure of the fan to turn on. Keep an eye on the fan as the engine warms up.
  • Leave the engine run for few more minutes. Ask your helper to keep focus on the gauge and temperature light. If the temperature warning light glows or the temperature gauge approaches the hot mark, turn off the engine.

Cooling  Fan Switch Vehicle

  • During all this time you keep an eye on fan, if it spins, the cause of overheating does not lie with the switch.
  • If in other case fan does not rotate, turn off the engine and wait foe the engine to cool down before testing the switch.
  • Once the engine cools down, trace the wire from the fan motor to the electrical connector.
  • Disconnect the fan from the electrical mechanism by pulling apart the connector.
  • Find the wire from the connector to where it attaches to the cooling-fan switch, which is attached either into the tank of the ra­diator or into the engine.
  • Remove the wire of the cooling-fan switch.
  • Unfasten the switch from the radiator or from the engine with the help of wrench.
  • To make sure that either the switch is working or not places it in water pan, but keep the terminals (some switches have one, others have two) outside the water. Placed a kitchen thermometer in the pan and adjust pan on kitchen-stove burner.
  • Use ohmmeter to test the switch. If the switch has one terminal, touch one of the ohmmeter probes to the terminal and touch the other probe to the threads. If the switch has two terminals, touch each ohmmeter probe to a terminal. The ohmmeter should display an infinity reading.
  • Lit up the burner and wait until the thermometer indicates the water temperature reached at 220°F. Repeat the ohmmeter test. The ohmmeter needle would swing to 0 or nearly to 0. If it doesn’t, the switch is defective.

After it is confirmed that the switch is defective, buy a replacement specified for the cooling system of your vehicle. To prevent the leak in future coat he threads of the new switch with pipe thread sealer or wrap them with Teflon plumbing tape. Screw the switch in place by hand until it is finger-tight. In the end tighten the switch back to its place firmly with the help of wrench.

To make sure for certain leakage, fill the radiator with antifreeze agent (coolant). Start the engine, leave it on for some time and after awhile turns it off. Make sure that there is no leak.