The cooling system is vital in maintaining optimal engine temperature and preventing overheating in automobile mechanics. One critical component of this system is the engine fan, which is responsible for dispersing excess heat generated by the engine. After shutting off the ignition, it is not uncommon for the fan to continue running briefly.
In such conditions, the thermostatic switch and temperature sensor come into play, signaling the engine fan to engage and stay on for an extended period. This continuous operation ensures that the engine oil maintains its optimal viscosity and prevents the engine from becoming excessively hot on very hot days.
The fan’s operation relies on electrical wires and electrical components, like the fan relay, which controls its functioning. A faulty relay or a bad temperature sensor can disrupt the expected behavior of the engine fan, causing it to run longer than necessary or cannot turn off promptly.
Certain Mercedes Benz vehicles and many modern cars feature the same pin design, which allows the car’s radiator fan to stay on even after the car has been turned off, serving as a precautionary measure against residual heat.
In our guide, you can learn more about how long radiator fan stays on after car is off, according to the coolant temperature and the engine’s working condition. By the end, you’ll better understand why radiator fan stays on while driving and if you have an issue when your engine fan stays on running continuously. (Read Can You Mix Ethanol And Non Ethanol Gas In Car)
Why Does My Cooling Fan Keep Running After the Car is Shut Off?
The cooling fan in your car plays a crucial role to keep the engine cool on hot days or after a long trip. However, it can be concerning when the engine cool engine fan continues to run for an extended period when you turn off the ignition. You could find lower radiator hoses scorching hot when the engine works hard or a water pump fails.
There are several potential causes for a cooling-down fan to stay on after the car is shut off, and for a short period, it is perfectly normal.
Let’s look at two common culprits why the fan on the car stays on:
1. Faulty Temperature Sensors
One reason the fan runs continuously is faulty temperature sensors. The fan relies on the feedback from these sensors to regulate its operation. This can be because of a coolant temperature sensor, malfunction or wiring issues causing the fan to stay on, or even coolant leaks that make the coolant reservoir empty.
2. Issues with the ECU Unit
The Engine Control Unit (ECU) controls various functions within your car’s computer, including the cooling fan.
If the ECU unit develops a fault, it may not signal to turn off the fan when it should. This can lead to the fan running even after the car is shut off.
How Long Should a Car Fan Run After the Car is Turned Off?
Under normal circumstances, a car fan should stop running within a few minutes after the engine is turned off. The exact duration can vary depending on the car model and how long the vehicle has been driven. In most cases, 2-3 minutes of the car fan running even after shut off is ideal, but it can extend up to 5 minutes.
However, if the fan continues to run for over 30 minutes, it is recommended to disconnect the battery terminal, especially the negative side, to prevent battery drain. (Read Do Ceiling Fans Help With Humidity)
Should the Radiator Fan Be Running All the Time?
No, the radiator fan should not be running all the time. Its primary function is to help maintain the engine’s ideal temperature. When the engine is started, the fan does not immediately turn on, as there is no heat buildup to dissipate. Instead, it typically starts running a few minutes after the engine is started.
On many cars, if you notice the radiator fan continuing to run even after the engine is shut off, it may show a potential issue. It is advisable to check for a low coolant level. A low coolant level can cause the engine temperature to rise and cause the fan to run until it reaches a certain temperature.
A coolant leak or a clogged system could cause this situation.
How Often Should the Cooling Fan Come On?
The cooling fan should come on when the engine has been idling for over 20 minutes. Electric fans connected to a temperature switch determine when it should activate.
Typically, there is a temperature threshold above which the fan will automatically turn off the ignition when on.
You can perform a simple test to check if your cooling fan functions correctly.
- Start the car with the AC switched off and wait until the temperature gauge reading reaches the normal operating temperature.
- At this point, the cooling fan should typically turn on. If the temperature rises too quickly or exceeds the optimum coolant level? It is advisable to check the coolant level, as a low coolant level can cause rapid overheating and engine issues.
Note: If the engine is boiling, it needs cold air to help it cool; otherwise, it could be damaged if the fan stopped working. In addition, if something causes the fan to stay on, it would be a cold start, or you have a dead battery if the fan still runs all the time.
Should the Radiator Fan Turn On When AC Is On?
Yes, the radiator fan connected to the AC system should turn on when the AC is switched on. The AC removes heat from the car’s interior, and the fan helps the cooling process. However, the fan connected to the coolant and temperature system will turn on only when enough coolant circulates and the temperature rises above a certain threshold.
When the AC is turned on, the AC compressor pushes the refrigerant through the system, generating heat. This heat needs to be dissipated so the radiator fan associated with the AC system turns on to help cool down the condenser. The condenser handles the coolant fans from releasing excess heat from the refrigerant.
When the AC is switched on, the radiator fan turns on to assist a hotter engine by cooling the condenser. However, based on the engine’s coolant temperature sensor, the radiator fan connected to the coolant and temperature system turns on. (Read Does Opening Windows Reduce Radon)
How Do I Know If My Cooling Fan Relay Is Bad?
If you suspect a faulty cooling fan relay, there are a few signs you can look out for. One of the first indicators is an abnormal rise in temperature on the temperature gauge. If the temperature quickly climbs above the standard limit, it could show an issue with the cooling fan relay.
Another sign of a bad fan relay is the fan not functioning at all or malfunctioning. If the cooling fan doesn’t turn on even after 15-20 minutes of starting the car? It might suggest a potential problem with the cooling fan relay or the water pump.
Similarly, if the fan doesn’t turn off after the car’s battery has been shut off, it could also be a faulty engine fan relay symptom. These signs should be addressed promptly, as an overheated car engine can lead to permanent damage. It’s advisable to consult a car mechanic to diagnose and fix the engine cooling fan and relay issue.
What Does A Bad Radiator Fan Sound Like?
When a radiator fan is malfunctioning, it may produce unusual noises. Typically, radiator fans operate smoothly unless there are issues like bent blades or other damage.
If the blades cannot be corrected, replacing the fan with a new one might be necessary. To inspect the fan blades, open the hood of your car and visually check for signs of bending. Even a minor bend in one place can cause the fan to vibrate when it’s switched on.
Can You Drive With A Bad Radiator Fan?
While driving for short distances with a malfunctioning radiator fan is possible, it is not recommended. Driving a car with a faulty radiator fan can lead to an engine overheating. The fan maintains the engine’s operating temperature and prevents overheating issues.
The thermostat controls most fans, so if the fans cannot run, the problem may lie with either the thermostat sensor or the engine fan itself. Excessive engine heat can cause the car’s fan not to expel coolant, and engine damage may occur in the worst-case scenario.
Do Both Cooling Fans Run At The Same Time?
Yes, both cooling fans should run simultaneously. One engine cooling fan stays and is controlled by the AC system, while the engine’s temperature regulates the other.
- If you are idling and only the AC is on, only the AC cooling fan may run.
- Only the engine or radiator fan may run if you drive on a freeway without the AC switched on.
A malfunctioning cooling fan relay can cause either or both fans to stop working correctly. If either fan cannot function as expected, check the cooling fan relay to determine the cause of the problem. (Read Combustion Air Switch Failed To Close)
How To Fix A Cooling Fan That Keeps Running?
If your cooling fan continues to run even after the engine has been powered off, it may show a problem with the relay cooling system.
Here are a few steps you can take to assess the issue and potentially resolve it:
- Check the coolant levels of water pump in your car. If the levels are low, it could trigger the fan to run continuously.
- Inspect the cooling fan relay for signs of damage or malfunction. A faulty relay can keep the engine cool fan to keep running.
- If you’re comfortable working with car electrical systems, swap the relay with another identical relay (like the horn relay) to test if the problem lies with the relay itself.
If the issue persists, seek help from a professional mechanic.
