Will a bad thermostat cause the fan not to work?

Asked By: Pierre Jacquemard | Last Updated: 6th April, 2020
Category: home and garden indoor environmental quality
4.9/5 (2,215 Views . 43 Votes)
If the thermostat is stuck open (allowing coolant to flow) it can cause the engine to run cooler than normal so obviously the fan wouldn't come on..but not like the engine/coolant can be running too hot and the thermostat somehow effects the sensor reading or operation of the fan.

Click to see full answer


Likewise, what causes a cooling fan not to work?

A fan failure, or a failure of the fan relay or control circuit is bad news because it can allow the engine to overheat. Engine thermostat is stuck OPEN (engine never gets hot enough to turn on the fan) Faulty fan relay. A wiring problem (blown fuse, loose or corroded connector, shorts, opens, etc.)

Furthermore, what are the symptoms of a faulty cooling fan switch? Several symptoms may point to a bad or failing thermo coolant fan switch.

  • Engine overheating. Engines generate an enormous amount of heat and as a result are subjected to very large temperature swings if this switch does not operate effectively.
  • Check Engine Light comes on.
  • Broken or shorter signal wire.

Keeping this in view, what are the symptoms of a bad thermostat?

There are several common symptoms associated with a bad or failing thermostat that will alert you that service is due.

  • Temperature gauge reading very high and engine overheating.
  • Temperature changing erratically.
  • Coolant leaks around the thermostat housing or under the vehicle.

Can I drive my car if the fan is not working?

Yes, you can drive your car without a radiator fan, but you never should. Your vehicle's cooling system is crucial to its performance, and every time your engine overheats, you cause damage.

35 Related Question Answers Found

Where is the cooling fan sensor?

The cooling fan relay is normally located in either the underhood fuse and relay center or mounted to the electric fan assembly behind the radiator.

Should radiator fan run when AC is on?

Both radiator fans should always run when the AC compressor is engaged. Both radiator fans should always run when the coolant temperature sensor in the bottom tank of the radiator reaches about 212*F.

Is there a fuse for the cooling fan?

A cooling fan relay is used on vehicles that have an electrical fan to cool the engine. The cooling fan relay is normally located in either the underhood fuse and relay center or mounted to the electric fan assembly behind the radiator.

How do I test my electric radiator fan?

How to Check a Radiator Fan
  1. Determine whether your radiator fan is manual or electric.
  2. To check an electric radiator fan, start the car and let it get up to the temperature where the fan normally kicks on.
  3. Use the volt meter to test if there is power to the wires.
  4. Normal voltage for a radiator fan is around 12 volts.

How do I know if my coolant temperature sensor is bad?


Signs of a bad Engine Coolant Temperature Sensor
  1. Poor Mileage.
  2. Check Engine Light Activates.
  3. Black Smoke from the Exhaust pipe.
  4. Engine Overheats.
  5. Poor Idling.
  6. Do not Use Tap Water to Refill Radiator.
  7. Fix Oil Leaks and Gasket Immediately.
  8. Check for Coolant Leaks.

Does the coolant temp sensor control the fan?

The sensor works by measuring the temperature that's being given off by the thermostat and/or the coolant itself. The temperature is then sent to the on-board control system. As the control system receives the temperature from the CTS, it may trigger the cooling fan to either shut off or turn on.

How do you test a cooling fan?

How to check your car's cooling fan
  1. Set the car heater to cold.
  2. Run the car until the engine reaches normal temperature.
  3. Watch your temperature gauge – don't allow the car to overheat.
  4. The cooling fan should cut in automatically and the temperature gauge drop back to normal.

How do I know when my water pump is bad?

Here are some common symptoms that hint towards having a bad water pump:
  1. Coolant leak at the front-center of your car.
  2. Water pump pulley is loose and making whining sounds.
  3. Engine is overheating.
  4. Steam coming from your radiator.

How do you know if your thermostat is stuck closed?

Check the radiator hoses for differences in temperature. If one (usually the top) is cooler, but the bottom is burning up, that indicates the thermostat is stuck closed as well. Do not stick your hand near the front of the engine while the fan and belt are moving, and never remove the radiator cap from a hot engine.

How do I know if thermostat is not working in car?


If you see your temperature gauge going into the red within the first 15 minutes of driving, your thermostat may be bad. Generally, if your vehicle is overheating within 15 minutes or so of driving it, this may be a sign that the thermostat is stuck. Step 2: Check the radiator hoses.

How do I test my thermostat?

Here's how to test your thermostat to see if it works:
  1. With the power to the furnace off, remove the thermostat or thermostat cover to expose the wires.
  2. Unscrew and remove the wires from their terminals.
  3. Twist the bare ends of the two wires together.
  4. Turn the power to the furnace back on.

How do I know if my thermostat is working?

4 signs your thermostat is bad
  1. Sign #1: Your thermostat has no power or is unresponsive.
  2. Sign #2: Your heater or A/C won't turn ON.
  3. Sign #3: Your A/C or heater runs constantly and won't turn OFF.
  4. Sign #4: Room temperature and setting don't match.
  5. Step #1: Make sure thermostat is on the right setting.

Can you drive with a bad water pump?

Hey there, To answer your first question, yes, it is very possible to drive a car without a water pump. If you plan on keeping your car, then you definitely need to have a new water pump installed, flush out the coolant system, and make sure all the coolant hoses are clean and free of holes.

Can a stuck thermostat fix itself?

You can either replace the valves with new ones or work the valves back into a position where they can move up and down more freely. Replace the thermostat. This is the last thing you want to do, but if the hoses do not show a blockage or coolant hindrance then the thermostat itself may be malfunctioning.

How can you tell if your engine coolant temperature sensor is bad?


Symptoms of a bad or failing coolant temperature switch (sensor)
  1. Poor fuel economy. One of the first symptoms associated with a problem with the coolant temperature sensor is poor fuel economy.
  2. Black smoke from engine. Another symptom of a possible problem with the coolant temperature sensor is black smoke from the vehicle's exhaust.
  3. Overheating engine.
  4. Check Engine Light comes on.

How much is a cooling fan relay?

So, when the cooling fan relay stops working, the coolant can get too hot, and the car can overheat. To get your cooling fan relay replaced, you will pay, on average, $80-$160, depending on the type of car you have and the mechanic's fees. The labor should cost around $70, while parts should run you $10-$50.

How long can a fan run continuously?

When you set your fan to “ON,” you're telling it to keep running 24 hours a day, 7 days a week, regardless of the heating or cooling setting.