You switch off the engine, lock the car and walk away. But you can still hear the radiator fan humming away under the bonnet. One minute, two, five. And now you're wondering if something's wrong. Don't worry, sometimes it's perfectly normal. But! There are faults that can leave you with a flat battery by morning. So if your VW radiator fan keeps running, it's worth knowing the difference.
When is it normal for a VW radiator fan to keep running?
If you've been driving in hot weather, on the motorway, climbing a steep hill or giving the car a bit more throttle, the engine and turbo will be pretty hot. That's why the car lets the fan carry on running after you've switched off the engine. It needs to cool things down. The fan can run for up to around ten minutes. On diesels, this can also happen if you've interrupted a DPF regeneration.
When should you start worrying?
- The fan comes on every time you switch off the engine, even after a short drive when it's cool outside.
- It keeps running for more than 15–20 minutes without stopping.
- It immediately runs at full speed when you start the engine from cold.
- You come back in the morning to find a flat battery.
- The temperature warning light or check engine light comes on.
What could make the radiator fan behave like this?
- The fan control module has failed and isn't switching the fan off.
- The temperature sensor is faulty.
- The air conditioning sensor is sending incorrect readings.
- The coolant level is low or the thermostat is sticking.
If the radiator fan doesn't come on at all and the engine starts getting hot in traffic, stop. That's more dangerous than a fan that won't switch off. You're risking serious engine overheating.
How do we check the radiator fan?
- First, we read the fault codes from the engine and air conditioning systems.
- We check what the temperature sensors are reporting and compare their readings with the actual temperatures.
- We check what's controlling the fan and how it's being operated.
- We check the coolant level and test the thermostat.
Advice from Kris Mladenov: If the fan keeps humming after you've switched off the engine, don't rush to grab your multimeter and start checking the battery. Give the fan a chance to stop on its own. If it switches off within ten minutes, there's usually nothing to worry about.
If your VW's radiator fan won't stop running, or it won't come on at all, bring your car to Das Auto Service. We'll check the fan controls and sensors and work out exactly what's causing the problem.
What will you find in our shop?
Genuine VAG G12Evo coolant G12E050A2 1.0l
Genuine G12evo coolant. Keeping the coolant at the correct level and in good condition helps your car's cooling system do its job properly.
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Frequently asked questions
Is it normal for the radiator fan to run after switching off the engine?
Yes. If you've been driving in hot weather or at higher speeds, the fan can keep running for around ten minutes.
Can the radiator fan drain the battery?
Yes. If a fault stops the fan from switching off, it can leave you with a flat battery.
What should I do if the radiator fan isn't working at all?
Keep an eye on the temperature and bring the car in so we can check it. If the engine starts overheating, stop.