Radiator Fan Relay Replacement Cost Estimate

A technician will check the engine coolant level to make sure that overheating is not happening because of a loss of coolant. Next, the technician will check for a blown fuse. If the fluid is full and the fuse is intact, the technician will remove the relay and use a multimeter to make sure that the relay is getting voltage. The relay will also be checked with the multimeter. It may also be tested by triggering it with another power source to see if it switches properly. Sometimes the technician will start the engine first and warm it up to observe the temperature gauge and check the fan operation to verify the condition. If the fan does not kick in when the engine temperature rises to a specific level, the relay is checked.

Replacing the relay is simple: like a fuse, it is pulled out of the fuse box (its usual location) and replaced with a new one. Diagnosis is the more challenging part of the repair.

If the engine overheats while driving, the vehicle should be pulled over and the engine turned off as soon as is safely possible. If the vehicle needs to be driven to a safe stopping point, proceed at a low speed and avoid stop and go traffic where airflow through the radiator is diminished.

An engine in a late model vehicle is designed to run somewhere between 195 and 220 degrees. But the fluid in the cooling system can rise well in excess of 220 degrees when the engine overheats. This produces steam that will cause severe injury from scalding if the system is opened when hot and under pressure. Burns are possible as the engine components are also at a high temperature. Extreme caution should be exercised when working on a hot engine, especially one that is overheated. If steam is seen coming from under the hood, the engine should be allowed to cool for at least a half hour before the hood is opened, and the radiator cap should not be removed until the engine is cool enough to touch with a bare hand.

Anyone who can change the fuse in a vehicle can change a relay if it is located in the fuse box. On the other hand, accurate diagnosis of the cooling system is not only challenging and potentially hazardous, it is essential for proper engine function. Misdiagnosis that leads to an engine overheating is not just an inconvenience, it is a mistake that can lead to thousands of dollars in engine repair or replacement.