The car radiator fan uses 12V and relies on the car battery power to run. It is supposed to receive a signal from the engine coolant temperature sensor to start running but in some cases can run continuously and drain the battery flat!
What signs show that there’s an issue with the fan running? What causes it?
Read on to find out why the fan may run continuously and for tips, you may be able to use to fix it.
How to Tell the Radiator Fan is Running Continuously
The radiator fan usually stops after the engine is turned off or continues to run for a short time if the engine is hot. If on the other hand, it continues running on high with the engine turned off even when the engine is cold then there’s a risk that the fan will drain the car battery flat!
1. Do you hear the sound of the radiator fan running even with the ignition off? Open the hood. The radiator fan is mounted at the back of the radiator. You should be able to see the fan blades spinning and the whirring sound from the fan!
2. Does the fan continue running even after 5 minutes?
If so then there’s a problem with the radiator fan.
What Causes a Radiator Fan to Run Continuously and Drain the Car Battery (Ignition Off)?
If the radiator fan runs all the time even after the engine has been turned off then it will drain the car battery. But why does the fan stay on?
Here’s what might be the problem and what to check.
1. Faulty radiator fan relay. The relay contacts may be stuck and continuously supply power to the radiator fan irrespective of whether the ECU is signaling the fan to stop.
Location of the radiator fan relay
The radiator fan relay may be faulty. The relays are usually located under the hood, on the right side of the car, near the battery. There’s a fuse/relay box. The top cover of the box shows the layout of the fuses and relays. Refer to it to locate the fan relay.
Suggestions
Unplugging the radiator fan relay, cleaning the contacts, and reseating it may fix the problem. You may have to relay the radiator fan relay with another to get it working.
2. The fan control module connections might be loose or the module is faulty. Try unplugging, cleaning the connection pins, and reconnecting again. Check if it clears the problem.
It is possible that the fan control module is faulty and needs to be replaced. You’ll need to locate the fan control module for your specific brand and model of car.
Related Topics
1. How Long a Car Battery Lasts with the Radiator Fan On?
An engine cooling fan running at full speed can run for up to 4-5 hours before a 55 Ah battery capacity is discharged to 50% of its capacity.
Actual runtime on the battery depends on battery capacity, the state of charge of the battery, and the fan speed. Expect the car battery to last longer with a higher capacity battery or if the fan speed is lower.
How Much Power (watts) Does a Radiator Fan Draw
An engine cooling fan can draw as much as 80 watts (depending on the model) at 12V when running at full speed. Check the radiator fan specifications to confirm the actual power draw of the radiator fan.
2. What Causes a Radiator Fan to Run Nonstop (Even when Ignition is On)
If the radiator fan runs nonstop even when the car ignition is turned off, it may be:
- The engine coolant temperature sensor is faulty or possibly a broken wire connecting to the sensor could be the issue.
- Check for a stuck radiator fan relay. Unplugging it, cleaning the contacts, and plugging it again has worked in some cases. It is possible too that the relay may be faulty and needs to be replaced
- Another possible reason is that the radiator fan is faulty.
Do not hesitate to contact a qualified auto mechanic.
Final Word
If the radiator fan is draining the battery flat, it may be the fan relay is stuck and needs to be replaced or that the fan control module is faulty and needs to be replaced.
Always contact a qualified auto mechanic for assistance.
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