Causes & Solutions for a Bad Radiator Fan
Blown fuse Like every other electrical component in a vehicle, the radiator fan has a dedicated fuse. If that fuse is blown, the fan won’t be able to turn on. Refer to your car’s manual to find the fuse layout. Then, with a cold engine, pop the fuse box and gently pull out the fuse for the radiator fan. Hold it up to a light. If the wire inside is broken, replace the fuse. If the wire is connected, your fuse is fine. The fix: Purchase a replacement fuse for your vehicle and insert it into the port for it. If you don’t want to do it yourself, see a mechanic. This is an easy, fast fix for them. The cost: A new fuse shouldn’t cost you more than $10 or so. If you have a mechanic do this for you, it may run $50-150.
Dead radiator fan motor The radiator fan has a dedicated motor responsible for powering it. If the radiator’s fan motor has failed, the radiator won’t turn on when it needs to. Unfortunately, this can be difficult to diagnose on your own so see a mechanic for this one. The fix: A mechanic will test the radiator motor and replace it if necessary. The cost: A new radiator fan motor may cost $500-750. A big chunk of the cost here is the part itself, since radiator fans aren’t universal or interchangeable.
Faulty fan relay The fan relay is a switch that turns on when the fan is told to turn on by the ECM (engine control module). Basically, the relay closes the circuit necessary for the voltage to reach the fan motor. If the relay is stuck or damaged, the radiator fan won’t be able to turn. Just FYI, a bad fan relay can also cause a radiator fan to keep running even when it shouldn’t be. If you ever encounter a fan that won’t turn off, it’s probably the relay. The fix: The relay needs to be replaced. See a mechanic to have the relay inspected and replaced. The cost: You’ll probably spend $150-300 on a new fan relay.
Bad ECM Also known as an engine control unit (ECU), the engine control module (ECM) is basically your vehicle’s computer. It monitors the engine and transmission so that your vehicle knows if there’s something wrong. It also sends user inputs to the relevant systems so that your car operates the way you expect it to. If the ECM has an issue communicating with the radiator fan, it may not work as intended. The fix: The ECM is a relatively complex system, so see a professional mechanic to have it inspected. It either needs to be repaired or replaced. The cost: It depends on what the primary issue is. If it’s just a minor repair, it may cost $200-500. If the entire ECM needs to be replaced, expect to spend around $800 on a new unit.
Physical damage to the fan The radiator fan sits behind the grill on the front of your vehicle (either behind the radiator fins or in front of them). When you drive, all kinds of rocks, bugs, dirt, and dust kicks up into your radiator. If something hits your radiator fan, it could damage the fan itself and prevent it from kicking on when it’s needed. The fix: It’ll likely be easier for a mechanic to replace the entire fan unit versus repairing the damaged fan. The cost: This can cost anywhere from $100-500 depending on how hard the fan is to access and how complex the make and model’s radiator fan is.
Damaged wiring As a vehicle component that requires a fuse, there’s a wire running from the fan to the fuse box somewhere in your vehicle. If a squirrel or rat has decided to nibble on that wire or it has simply degraded over time, it could keep your radiator fan from operating correctly. The fix: The wire needs to be replaced. See a mechanic to have them run a new line from the fuse box to the radiator fan. The cost: Expect to spend $50-200 on a new wiring setup for a radiator fan.
Signs the Radiator Fan Isn’t Working
Engine overheating in general is a sign of a bad radiator fan. The radiator and radiator fan are responsible for absorbing all of the heat from your engine (via coolant) and blowing it away from your vehicle. So, if your engine begins to overheat, it’s a big sign something could be going on with either your radiator or radiator fan. If the engine starts to run too hot, an emergency temperature warning will pop on. It looks like a little thermostat with two waves underneath. If you notice overheating issues, start by checking your coolant. A coolant leak or old coolant are much more likely causes of engine overheating than a bad radiator or radiator fan.
The radiator fan is especially likely to be bad if you overheat at low speeds. The radiator fan isn’t necessary when you’re driving at higher speeds, so it usually only kicks on when you’re driving at a lower speed. As a result, it’s almost certainly a bad radiator fan triggering the overheating if the overheating occurs when you drive at low speeds and dissipates a bit when you’re going faster.
You may see the fan not spinning when the engine is idling. Some radiator fans sit on the inside of the radiator (to push air out), while others sit in front of the radiator (to pull air out). If your fan is on the front or your radiator fins aren’t very thick, you may be able to see the radiator fan from inside the grill. Since the radiator fan only kicks on at idle or low speeds, you may be able to see if the radiator fan is working by just turning the car on and monitoring the fan. If the fan never kicks on after the engine has reached its normal idling temperature, the radiator fan is probably not working correctly. This may not work if it’s under 60–70 °F (16–21 °C) outside. It just may never get hot enough to force the radiator fan on.
How does the radiator fan work?
The radiator fan helps cool the coolant when driving at low speeds. When you’re driving at high speeds, there’s a lot of air flowing in through your car’s grill. That air helps pull the heat off of the radiator and cool your vehicle. But at lower speeds there’s no airflow. To help keep heat from building up in the engine bay, the radiator fan turns on at low speeds to provide additional help. The radiator fan is especially helpful in hotter weather when the engine gets hot fast at lower speeds. If you live in a really cold climate, you may never even notice the radiator fan isn’t working.
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