How to Replace Cooling-Fan Switch in Your Car

Normally, the vehicles with electric cooling fans have switches which are there to check the temperature of the coolant and switch the fan on when the temperature reaches to a preset level. It is important to keep the coolant at an optimum temperature otherwise the coolant will boil and the engine will also overheat.

An ohmmeter is required to check the switch. If you found your switch faulty, here are given the simple steps to replace or check the switch for any damage or fault.

Directions

• Park the car on the level surface and engage the parking brake. Switch the engine on and examine the fan as the temperature of the engine rise.

• You may need to wait for some time. During that time, ask your helper to sit in the car and keep an eye on the temperature warning light on the dashboard. Tell him to turn the engine off, if the light turns on or the temperature needle approaches the HOT mark.
• If the fan doesn’t respond during this period, the cause of overheating is not associated with the cooling fan switch.
• Turn the engine off and wait for some time to let the engine get cool down. Now you need to check the switch by removing it.
• Trace the wire from the fan motor to the electrical connector.
• Remove the connector and detach the fan from the electrical system. Make sure that you have already disconnected the negative cable from the battery before working on electrical system of the car.
• Now look for the wire that is attached to the cooling fan switch. You may find it screwed into the tank of the radiator or into the engine.
• Detach the wire from the cooling fan switch.
• You need a wrench to unscrew the switch from the radiator tank or from the engine.
• Switches are come with either one switch or two. Place the switch in a pan of water so that its terminal or terminals remain outside the water. Now place a kitchen thermometer in the pan of water and place it on the kitchen burner.
• Now you need to check the switch with an ohmmeter. For one terminal switch, connect the one probe of the ohmmeter with the terminal and other probe to the thread. For two terminal switches, connect both the probes of ohmmeter with terminals. The meter should display infinity reading.
• Turn on the burner and when the thermometer indicates the temperature has reached to 220°F, repeat the ohmmeter test. The needle should move to or nearly to 0. Otherwise, switch is defective.
• Purchase a new switch from the dealership or any auto parts store. Cover the threads of new switch with Teflon plumbing tape or pipe thread sealer to prevent leak. Use your hand to fasten the switch in its place first, and then fasten it properly with a wrench.
• Refill the radiator with fresh coolant. Switch the engine on and leave it on for few minutes. Turn off the engine and check for any signs of leak.