Cooling & overheating

Radiator cooling fan not turning on

If the electric cooling fan doesn't run when the engine gets hot or the AC is on, the engine can overheat especially in traffic or at idle, and the cause is usually a blown fuse, a bad relay, or a failed fan motor.

Difficulty
Moderate
Time
20–40 minutes to diagnose
DIY cost
$10–$60
Pro cost
$150–$500

Symptoms

  • Temperature gauge rises especially in traffic or at idle but is fine at highway speed
  • No fan noise or visible fan movement when the engine is warm
  • AC may blow warmer than usual since some fans also support AC condenser cooling
  • Overheating warning appears mainly in stop-and-go conditions

Likely causes

  • CommonBlown fuse for the cooling fan circuitA dedicated fuse protects the fan motor circuit and can blow from a short or age.
  • CommonFailed cooling fan relayThe relay that switches power to the fan motor is a common failure point and is relatively inexpensive to replace.
  • PossibleFailed coolant temperature sensorIf the sensor that tells the computer to turn on the fan fails, the fan may never get the signal.
  • PossibleFailed fan motor itselfThe motor can burn out or its bearings can seize after years of use.
  • Less commonWiring or connector issue at the fanCorrosion or damage to the wiring harness near the fan can interrupt power.

What to do

  1. With the engine warm and running (in a well-ventilated area, staying clear of the fan), turn the AC on to see if the fan kicks on, since AC use often forces the fan on regardless of temperature.
  2. Check the fuse box for a blown fan-related fuse and replace it with the same rating if blown.
  3. Check for a cooling fan relay, often in the underhood fuse/relay box, and swap it with an identical relay from another circuit to test.
  4. Avoid idling for extended periods or sitting in heavy traffic until the fan issue is resolved.
  5. Have a mechanic test the fan motor directly with power to confirm whether it's the motor itself or something upstream.
  6. Replace the confirmed faulty component: fuse, relay, sensor, or motor.
  7. Recheck fan operation after any repair by warming the engine and watching for it to turn on as expected.

Tools and parts

  • Fuse puller/tester
  • Multimeter (optional)
Cooling fan motor or relaySearch: “radiator cooling fan motor [make model year]”

When to call a pro

See a mechanic if swapping the fuse and relay doesn't fix it, since testing the fan motor and sensor needs a multimeter and some electrical knowledge.

Safety

Use caution

Keep hands, tools, and clothing away from the fan area whenever the engine is running, since electric fans can start suddenly even with the engine off if the coolant is still hot.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.