Troubleshooting a Radiator Fan That Won't Start

A car engine.
  • 1-2 hours
  • Advanced
  • 0-40
What You'll Need

A radiator fan is important as it helps to circulate air within the engine of your vehicle and keep the engine temperature down. If the fan isn’t working, it could lead to overheating and cause damage to the engine which could prove very costly. When the radiator fan won’t start, what can you do? In many cases, the problem can be fairly simple and easy to fix. This can get you back on the road quickly without costing you too much money.

Step 1 - Do a Visual Check

It’s always worth opening the hood and checking manually that the radiator fan isn’t working. Many fans can be very quiet. If the engine temperature is high and the fan really is working, you’ll need to look elsewhere for the cause.

Step 2 - Check the Fuse

The biggest cause of a radiator fan not working is a broken fuse. To see if the fuse is intact and working, you’ll need to look at the fuse panel in your vehicle which will probably be under the hood. The actual location will be listed in your owner manual and will show which fuse works for which component.

The compartment should include a fuse puller. Use this to remove and inspect the fuse. If it’s intact, put it back. If it’s broken you’ll need a new fuse of the right amperage to replace it. Insert the new fuse then test your automobile again. When it reaches the right operating temperature, the fan should turn on.

Step 3 - Check the Wiring

A car engine.

The fan wires could also be the reason your radiator fan isn’t working. To begin, you need to unplug them. You’ll see that there are two wires, one of which is positive while the other one is negative. You need to use a voltmeter to see if they’re putting out 12 volts DC. If there’s no current, you’ll need to look at the fan relay as well as the fan wires.

The fan relay will be located under your vehicle hood. You will need to use the voltmeter to see if the current is running from the relay to the fan. If not, you’ll need to replace the radiator fan relay which is a simple job. However, if the voltage is running directly to your fan, your fan has probably died and will need to be replaced. If you’re doing the job yourself, make sure you buy the right fan for your vehicle with correct CFM.

Step 4 - Check the Temperature Sensor

The temperature sensor, which is located in the cooling system, performs an important function since it determines when the fan kicks in. To find out if the sensor is working, you’ll need to disconnect the wires from it and hold them together. If this makes the fan start, you have a faulty sensor and you’ll need to replace it.

Step 5 - Replace the Fan Clutch

The fan clutch holds the radiator fan to the engine's water pump and the springs can deteriorate or corrode over time. If you’ve tried the other items and can’t find the problem, replace the fan clutch to see if it resolves the problem.