Do Radiator Fans Run All The Time?

Do Radiator Fans Run All The Time?

Note: As an amazon associate I may earn a small commission from qualifying purchases if you click to amazon from my site and choose to make a purchase.You can read my complete affiliate disclosure for more details

Do Radiator Fans Run All The Time?

Radiator fans are commonly installed in heating and cooling systems to keep air moving around the unit.

Airflow limits heat transfer, which is why a well-regulated airflow can increase the efficiency of a radiator fan by up to 20% or more.

Modern homes are equipped with sophisticated heating and cooling systems that rely on using these devices to stay efficient. But, Do Radiator Fans Run All The Time?

No! Radiator fans are not constantly running and should only be used when necessary. They are usually used to help with air circulation and cooling during the summer when the air conditioning is not on or after a long drive where the radiator gets hot.

The fan draws hot air from inside your car through the front grill, forcing it out of your car for efficient cooling.

It does this manually or automatically, depending on what type of vehicle you have and what type of fan you have.

Manual fans are the most common type used for automobiles. You can manually turn on and off the fan by turning it on and off with your hand.

They usually have two switches; one turns them on, and one turns them off.

Manual fans are recommended only for older cars that don’t have air conditioning because they tend to take longer to cool the car down.

Automatic fans are used for newer cars that have air conditioning. They are controlled with a button or switch and can automatically turn on and off.

They usually shut off after a specific time, just like manual fans.

They are recommended for newer vehicles because they cool the car faster than manual fans, but there is less control over the fan’s operation.

Radiator fans can be beneficial when used correctly. They can be used in both manual and automatic ways, depending on what kind of vehicle you have.

They are usually more compact in newer vehicles and are usually controlled automatically by the air conditioning system.

If you want to keep your car running cool all summer, consider using a fan to help with cooling.

When Should The Engine Fan Run?

The engine fan should run at about 200 degrees Fahrenheit to keep your engine’s temperature at a safe level.

With an electric fan on the radiator or an air-cooled engine, the fan keeps cooling air circulating so that it will continue without burning out.

A car’s internal combustion engine produces heat in two ways: when gasoline mixes with air and burns and when parts of the engine rub against each other.

Do Radiator Fans Run All The Time?

The hotter the engine, the greater the friction; thus, a car’s temperature rises.

Once inside an air-conditioned car, a fan is ineffective if it cannot cool the engine sufficiently.

The temperature inside an automobile’s engine can reach as much as 2,000 degrees Fahrenheit during operation.

This temperature is high enough to melt some car parts if they are not cooled by circulating air.

When the engine is hot, and this temperature is reached when the car is stopped, the average operating temperature can make it impossible for a fan to cool the engine enough.

Then the only way to cool it down is with an air conditioner.

The hotter the engine, however, the more damage it can do to itself.

Once this begins, an overheated engine may develop high-temperature “thermal cracks,” which spread and cause an explosion or fire.

This can happen quickly, leaving little time to react.

Why Is My Radiator Fan Not Turning Off?

Your radiator fan is not turning off because it needs to cool down the house before it can turn off. You’ll want to ensure that your electric heater is off and no lights are glowing.

A radiator will automatically turn on when the temperature reaches a certain point, but it will shut back off once it reaches a set point. You should reset your thermostat if it doesn’t shut back off.

You might also have debris in your attic or insulation falling on your V condenser coil and interfering with the heating element. This will not allow your V to cool down and turn off.

Lastly, you could have a stuck thermistor spring that keeps the airflow from shutting off.

This would be a sporadic occurrence, but yours may be stuck so that it doesn’t go off when you are away from home.

Here are some tips to ensure your radiator fan turns off every time.

1) Do a basic tune-up of your AC condenser, fan, and ductwork before winter starts.

Even if you don’t believe it’s necessary, do a service before the season starts and have any issues fixed now instead of dealing with them later in the winter when they’re going to be much more expensive.

2) Clear any bird nests out of your attic and V condenser. Squirrels will hoard insulation, so if there is any in your attic, you’ll want to clean it up so they can’t stash it.

They are opportunists and will pick up insulation and bring it down.

3) Make sure your AC is running at the lowest temperature possible before winter starts and that the lowest temperature setting matches the indoor temperature before leaving your house.

4) Make sure all your lights are turned off in the house. This will prevent incandescent lights from turning on and using more energy than they should.

They will also affect the temperature of your air conditioner, which could make your system work harder unnecessarily.

5) Make sure all of your electronics are turned off. This includes any gaming consoles or computers that you may have in your house.

They will also affect the temperature that is being produced by your VAC unit. If they are not turned off daily, you could be paying extra for nothing.

6) Ensure all windows are closed when the AC is running. You do not want to have any open in summer because it will allow heat and cool air to come through.

You may be surprised how much your house can heat in the summer with just a few open windows.

How Do You Test A Radiator Fan?

Many people don’t know how to test a radiator fan, but it’s possible. If you have one that doesn’t work, check the fuse first and see if you’ve blown it.

If it’s still not working, ensure the wire going into the machine is adequately connected and needs a little slacker.

It might also be because debris blocks the airflow or something is overheating.

If this is the case, then taking the car to your nearest dealer and requesting they can fix it will be the best option. If you want to know how to test a radiator fan, here’s how to do it.

First off, you’ll need a temporary 12 Volt power source. You will need this for about 30 seconds because the test takes about three minutes.

This can be any device with a 12-volt battery; it doesn’t matter if it is a flashlight or an alarm clock.

Do Radiator Fans Run All The Time?

Now that you have your power source, turn it on. You’ll see that the fan should automatically turn on for about 30 seconds. This will show you if the fan is working or not.

The next step is to hold it in your hand with the other hand reaching over and putting the leads together.

This is easier said than done because there’s a right and wrong way to do this. If the fan works, you should get a spark that will turn off.

This is because the electricity will go through the fan, and you’ll have to turn it back on. Keep repeating this until you have found out whether or not it works.

Why Is My Radiator Fan Still Running When The Car Is Off?

Two possible explanations for why your radiator fan may run even when you’re not driving:

Your ignition may never have turned off. Secondly, your radiator fans may be running to help cool down the engine.

If you haven’t driven and your ignition has never completely turned off, the car will be in”limp home” mode.

Most cars and trucks enter this when you turn off the ignition without actually pushing down on the key. To enter limp home mode, all you have to do is leave your car idling.

If you’re sitting down, this can be a bit hard, but remember that the engine doesn’t always have to be running.

If you don’t put your car in limp home mode and your ignition has always been off, it’s possible that the coolant system isn’t getting enough air when the car is not in use.

This can lead to overheating of various components in the cooling system. In most cars, the radiator fan will still run idle when you’re not driving.

The best way to tell if you have an actual problem with your radiator fan is to jack up your car and take a look.

The motor that controls the radiator fan is attached to the top of the radiator, above and behind the grill.

If it’s not clicking on and off when you turn the ignition off and on, or if it appears otherwise damaged, it may be time for a replacement.

How Do I Know If My Radiator Fan Is Not Working?

You’ve just given your car a thorough wash and noticed the radiator fan is not working. If that’s the case, you have a few options for cleaning the radiator.

First and foremost, start by disconnecting the negative battery cable on your car to avoid any accidents due to metal parts touching each other.

After this is done, turn off any accessories such as lights or fans if possible so as not to cause harm if a spark occurs from loose wiring. 

You can also try manually engaging and disengaging the fan belt by slowly turning it in and out while listening for any clicking noises that may indicate it is stuck.

If this does not work either, you may have to go the drastic route of completely removing the engine and radiator to get access to the fan belt.

Most cars today are behind the front bumper, which is not easy to reach with a wrench.

Also, make sure to disconnect the battery and leave it disconnected for at least an hour or two before you do any work on your car.

This way so as not to accidentally start it or have some other accidents occur with metal parts touching each other.

Others may leave their car in neutral, which should disengage the transmission so as not to cause unnecessary wear and tear.

Once you have done whatever you feel will get your radiator fan working again, you can reattach your battery and put it back into drive to ensure everything is safe.

You can go on your merry way and enjoy being able to drive again as long as the radiator fan works.

Can You Drive A Car If The Radiator Fan Is Not Working?

Yes! Absolutely! You may notice a difference in the engine noise, but your car will still work.

To understand how this can happen, you first have to understand the role of the radiator fan.

The purpose of the radiator fan is to push air through the radiator system and cool down the engine before it becomes too hot and damages itself.

The radiator fan is always running, even in cold weather. But if your car’s engine is not working, the radiator fan will not be able to draw air through the radiator.

Now here’s how you can drive a car with a dead engine if the radiator fan is not working:

Step 1. Put up the windows. This will keep hot air from entering the passenger compartment and prevent it from heating up too much.

Step 2. Smash the windows or open the doors. The air will be forced through the open window, which will cool down the inside of the vehicle. You may experience quite a breeze.

Step 3. Stop all work on and around your vehicle until your car is thoroughly cooled down. This way, no parts in your car can get too hot, and you don’t risk damaging them further.

Step 4. If the car has a heater, turn it on. This will ensure that your car will be warm even though you can’t drive it or start it.

Step 5. Walk outside or set out on a predetermined route. Feeling a breeze? You’re not alone!

Step 6. Even if your car is not in good working condition, you can still knock out some great exercise.

Can A Broken Radiator Fan Cause Overheating?

Yes! Radiator fans are responsible for directing cool air through your vehicle’s radiator to help it cool down.

If the fan is broken, it won’t be able to circulate the air effectively, and your engine could overheat.

It’s essential to identify whether or not a radiator fan is faulty before it causes more expensive damage!

For starters, have a mechanic scan for faults and give you an estimate. They can perform a fan replacement if the cost is within your budget.

If the estimate is more than you want to spend, try replacing the fan yourself. When the radiator fan is broken, your car may overheat and stop running.

However, if you were able to get some coolant into your engine and it’s still running, follow these steps to replace the broken radiator fan:

  • First, ensure that no coolant has leaked onto a hot engine or anywhere else, for that matter.
  • Next, put the car in neutral (don’t put it in a park) and open the hood.
  • Remove the radiator cap, drain and inspect your engine for leaks.
  • Seal off any leaks with a cloth or paper towel, and don’t touch the coolant with your bare hands. The coolant is extremely hot and could burn you.
  • Disconnect the fan from the motor by removing some bolts from its base plate. It should just pull straight out of its housing.
  • Next, remove the fan shroud (to get an idea of this, look at the wires and brackets connected to your old fan). You may have to disconnect some other parts too.
  • Finally, attach the new fan by reversing these steps. Install new bolts and tighten them down with a hammer or wrench. Don’t use a power tool, as it could overheat and cause more damage.

Symptoms of a Bad or Failing Cooling Fan Relay include:

  • No sign of power coming on when the engine is started.
  • Suddenly, the fan relay won’t work, no matter how often you turn it on and off.
  • The fan belt slips a lot.
  • The car suddenly runs very hot.
  • The temperature gauge goes up and down erratically.
  • The engine runs roughly or stalls.
  • Sometimes, the car will not start at all.
  • In some cases, the engine has been known to stall and not restart for several days.

If you check your owner’s manual and look under the hood, you will find instructions on how to test your Camry cooling fan relay.

In most cases, jumping the two wire terminals in the relay with a screwdriver. This will turn the fan on high speed for a few seconds, so be careful not to touch it.

Your relay is good if the fan comes on high speed and then goes off after a few seconds.

If the cooling fan stays on high speed indefinitely or you do not experience any fan operation, your relay is wrong and needs to be replaced.

Does A Radiator Fan Need A Relay?

Yes! A radiator fan needs a relay. The proper function of a radiator fan is to draw room air out from the front of the radiator and blow it through the house.

If there’s no air intake, or if that intake isn’t working correctly, your radiator isn’t getting enough fresh air, which could cause overheating of your home.

A heating system with a poorly functioning evaporator or condenser may also overheat due to insufficient ventilation.

A radiator fan will operate at the same basic principle as an electric motor. The fan draws in outside air, which passes through a filter and then into coils inside the fan housing.

The air then flows out of the housing, through the ductwork, into your home via your venting system and blows through your vents.

But there is a slightly different kind of relay (or, more precisely, a sensor) designed to signal to the furnace when something like a radiator fan has done something.

This kind of “radiator relay” is called a “variable speed control.” It is the opposite of a “limit control,” which is used to sense when something like your blower motor has stopped operating.

Nowadays, pretty much all builders use variable speed controls.

Limit controls are more common in new homes because they have fewer moving parts and are cheaper and easier to install.

But they don’t work very well in older homes, especially if the blower motor is in the attic or basement rather than right next to the furnace or air handler.

How Does A Cooling Fan Relay Work?

The activated relay completes a circuit, allowing an electric current to flow through it and reach the cooling fans on the other side of the relay.

This has two effects. First, it provides power to the cooling fans. Second, it causes a magnetic field to produce a current in these two windings – one on each side of the relay.

The electrons that travel through this magnetic field are converted into electricity called an electromotive force (emf), which creates heat and soothes your skin on contact.

This effect is called the Faraday Effect.

In the case of this fan relay, the current creates heat, and so it serves to cool the device. This is also called a convection/radiant effect.

The fan then blows air into your room, so your skin is kept happy with cool air conditioning.

This fan relay has an internal electromagnet which creates a magnetic field that allows electrons to flow from one side of the relay to the other. This process produces heat.

The fan relay is a faraday (Faraday) effect cooling element, but it also serves to cool the device.

In this case, the fan does not cool the device but provides air flow that aids in cooling the device’s other fans.

Does The Coolant Temp Sensor Control The Fan?

Yes! The coolant temp sensor controls the fan speed. Coolant temperature triggers the cooling system to kick on in your car. As temperatures rise, so do your car’s fan speeds.

The process begins once the engine reaches a certain temperature called the “refer” point, which differs by year and model of vehicle.

But typically ranges from 100°C to 150°C depending on what type of cooling system you have installed in your vehicle.

(Your vehicle’s engine coolant has a built-in thermostat that senses and regulates the heat by decreasing or shutting off the flow of coolant.

If the engine gets too hot, a small amount of coolant is allowed to trickle into the engine via bypass valves. This keeps it from overheating.)

Once the engine gets too hot, the cooling fan speeds up.

This allows air to circulate between all parts of your cooling system so that water can be forced through your radiator, which is located in front of your engine block(s).

The water in your radiator is circulated by a fan belt attached to the engine; when you step on your vehicle’s gas pedal, the gear from the transmission turns the fan belt, which causes it to circulate.

Once the engine gets past it the temperatures begin to go down, your car’s cooling fan speeds do.

Example: If you have a 1.6l motor and a non-electronic cooling system, it should take about 3-4 minutes to reach its reference point.

If your vehicle is equipped with air conditioning, you may also notice that your fan speeds up to around 30 seconds after turning the air conditioning on.

This is because of the extra load you put on the engine once it’s running. (In other words, the air conditioning adds heat to your engine’s cooling system.

As temperatures rise, so do the engine’s fan speeds to achieve the same goal as your car’s cooling system.)

Once you turn the air conditioning on, it keeps the engine running at maximum speed for a short period.

Should The Radiator Fan Come On When The Car Starts?

Yes! Many people are unaware that their radiator fan should be coming on anytime their vehicle runs.

The radiator fan blows air through your radiator, cooling the water inside to keep it at a lower temperature.

This will keep you from over-heating even if your car is stuck in traffic or waiting at a stoplight while the outside temperature rises.

Some vehicles have a ‘fan only’ feature that will only run the fan when your car is running.

However, I do not recommend this since it isn’t necessary unless you have an additional cooling fan installed in your radiator.

By not having the non-operating radiator fan on, you risk overheating and damaging your engine if the temperature reaches over 200 degrees Fahrenheit for extended periods.

This is because a vehicle’s cooling system is designed to operate differently when the car is in motion and when the car stops.

When driving, the radiator fan should run for brief periods and will only come intermittently to cool the car down.

This is because your engine is moving, and even with a faulty radiator fan, you would quickly cool down your engine since it’s running so fast.

You can also control the vehicle’s speed and adjust the air conditioning or heat during normal driving, thus minimizing the risk of premature engine damage.

The reasoning behind having your car’s radiator fan come on only briefly while you are driving is that when you stop.

There is a period when you continue to move forward, but your engine is not doing anything. This period has been known as the “dead zone”.

Since the engine is not active, your vehicle’s cooling fan doesn’t do anything but run.

If you have your radiator fan come on only when you are moving, then there is a chance that it will overheat and damage the engine if it isn’t active while you are stopped.

Can Low Coolant Cause The Engine To Shake?

Yes! Low coolant levels can cause an engine to shake. The air conditioning system might also fail, and the engine’s radiator will have higher operating temperatures, which may lead to a blown head gasket.

There are a lot of causes of shaking that have nothing to do with low coolant.

So if you don’t have symptoms like overheating or blowing smoke from the tailpipe, it’s not likely that low coolant is your issue.

First, let’s look at low coolant levels. Check the Jaguar dealer manual that shows normal coolant levels at specific intervals:

The lower line is at dash level (you fill it yourself), and the upper line is for the air conditioner.

Jaguar recommends that you maintain this range of coolant to maintain proper engine operation and prevent scoring or chipping of cylinder liners.

Some Jaguar owners think that if the coolant level is fine, there shouldn’t be any problems with engine vibrations when the engine is running.

But what if that fine coolant level suddenly jumps up to a half-full level?

The cylinder head will still be perfectly smooth and flat, but the engine’s moving parts, like the pistons and connecting rods, might not be hitting dead on.

This is because there’s too much volume of coolant trying to cope with a small area. That can cause vibrations.

Can Low Coolant Affect Acceleration?

Yes! Next time your engine starts to drone or sounds a little different, try checking the coolant level.

Low coolant can cause overall engine damage if not rectified soon enough and affects acceleration.

A half-full tank means that you may be accelerating at half the amount of horsepower than you would if your engine had more than a quarter of a tank.

Since modern engines have computer chips to monitor and adjust for this, the engine may not feel much different to the driver, but your car will be damaged.

The coolant system is designed to keep the engine at a steady temperature by releasing or taking in liquid coolant at specific rates as engine speed varies.

A car uses around a quart of liquid coolant every 24 hours. The coolant is pumped around the engine by a system of hoses and pumps.

Computer components guide the hoses and pumps. If one part locks up, for example, the coolant will be released or taken in faster than usual to keep the system from freezing up.

When a car starts, it needs an amount of coolant in the engine to warm up from its cold state quickly enough to start running safely.

The cooling system will need more fluid if the car is not driven for a day or two.

If the engine overheats and coolant are lost, the computer will compensate by taking in more fluid.

But if the engine overheats again, the computer will begin compensating by releasing fluid back into the system more quickly than usual.

When the cooling system is nearly empty, the computer compensates more by releasing fluid more quickly. You can make many other subtle changes in how the computer reacts to problems.


Radiator fans are important for the proper functioning of a vehicle’s engine.

They can be replaced if faulty or damaged, but if you have a slight problem with your fan, there is no need to replace it immediately.

Recent Posts