Radiator Fan Not Working
The electric radiator cooling fan is what keeps your engine from overheating at idle and low speeds. When it stops working, the engine temperature climbs quickly in traffic — leading to overheating and potential head gasket damage.
Can I Drive?
In emergencies only. Keep moving — highway driving uses ram air instead of the fan. Avoid idling in traffic. This is a stop-driving issue because you will overheat quickly in any traffic situation.
Most Likely Causes
- 1
Failed fan relay
The fan relay is a small electrical switch that commands the fan on. They fail frequently and cost $10–$20 to replace. Check this first.
Often located in the underhood fuse box. Check your owner's manual for the location.
- 2
Failed cooling fan motor
The electric motor that spins the fan blades burns out over time. You can test it by applying 12V directly to the motor connector — if it doesn't spin, the motor has failed.
Fan motors are often sold as complete assemblies with the shroud.
- 3
Faulty coolant temperature sensor
The ECU uses the coolant temperature sensor to command the fan on. A faulty sensor gives the ECU incorrect data, preventing the fan from activating even when the engine is hot.
If the fan works manually (direct 12V) but not on command, suspect the sensor or ECT circuit.
How to Diagnose It
- 1
Let the engine warm up to operating temperature with the hood open. The cooling fan should come on. If the AC is on, the fan should run any time the AC is engaged.
- 2
Locate the fan relay in the underhood fuse box (consult your owner's manual). Swap it with an identical relay from another circuit (e.g., the horn relay — same amperage). If the fan works, the relay was bad.
- 3
Disconnect the fan connector. Apply 12V to the positive terminal and ground the negative. If the fan spins, the motor is good — the problem is in the circuit (relay, fuse, temperature sensor, or wiring). If the fan doesn't spin, the motor has failed.
How to Fix It
Failed fan relay
Fan relay replacement is the easiest fix — pull the old relay, push in the new one. $10–$20 part, 2 minutes to replace.
Failed cooling fan motor
Fan assembly replacement is straightforward. Disconnect the wiring harness, remove the mounting bolts (3–4 bolts), and install the new assembly. Usually 30–45 minutes.
Faulty coolant temperature sensor
The coolant temperature sensor is usually a $15–$30 part accessible from the top of the engine. Drain some coolant, unplug the sensor, thread in the new one, and refill.
Parts & Tools
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Mistakes to Avoid
- Don't idle in traffic with a known fan failure — you will overheat.
- Don't replace the fan motor without first testing the relay (saves money if the relay is the issue).
- Don't ignore a fan that runs continuously at full speed — that can indicate a stuck-closed thermostat.