Can A Bad Thermostat Cause Radiator Fan Not To Work?

Can A Bad Thermostat Cause Radiator Fan Not To Work

A bad thermostat stuck open won’t trigger the radiator fan because temperatures won’t rise enough. However, a thermostat stuck closed causes overheating, making the fan run continuously.

Thermostats are dangerous because they control the coolant flow. Therefore, every component that responds to the temperature in an engine may suffer once the thermostat malfunctions.

However, that doesn’t mean you should blame the thermostat for everything that goes wrong with the engine. The cooling system is broad. It has several components, each of which can disrupt the engine’s operations by allowing the temperature to skyrocket when it fails.

You should also keep in mind that radiator fans can fail for various reasons. This is why laypeople prefer to leave bad radiator fans in a mechanic’s hands.

A professional can perform a comprehensive analysis of the radiator, engine, and cooling system to identify the faulty part.

The Electrical Connection Between The Thermostat And Radiator Fan

Every expert says that coolant prevents the engine from overheating. The substance flows into the engine, picks up heat, and carries it away. How does it know that an engine is too hot? The thermostat has wax at its center that melts and expands when exposed to specific temperatures, opening a valve.

The open valve allows the coolant to flow. Once temperatures fall, the valve will close, restricting the coolant flow. The thermostat will open and close periodically while you drive to keep the temperature within the optimal range.

But if the coolant cools the engine, what purpose does the radiator fan serve? Avinash Gudimetla, K L Narasimha Murty, and C V Gopinath answered this question in this paper in the International Journal of Engineering Research and Technology. The radiator fan pulls air through the radiator panel to cool the engine coolant.

Admittedly, the paper is concerned with radiator fans in a Railway diesel locomotive engine. But a car radiator performs a similar function. The coolant doesn’t need the radiator fan to absorb the engine’s heat.

But what happens to the heat the coolant collects from the engine? Where does it go? A coolant can tolerate temperatures as high as 275 degrees F. The vehicle’s pressure will raise the boiling point by 45 degrees F.

But if the temperature keeps rising, the coolant will eventually boil, which is dangerous because it increases the pressure in a closed system. The vehicle needs to cool the coolant before it can absorb more heat.

Manufacturers use the holes in the grille and slats above the engine to achieve this objective. However, the holes and slats cannot cool the coolant without assistance. The radiator fan increases air circulation under the hood. It allows the radiator to lower the coolant’s temperature.

In that regard, the thermostat and the radiator fan work hand in hand to prevent overheating in the engine. One is useless without the other. The fan cannot cool the coolant if the thermostat won’t let it flow. The coolant will overheat unless the fan cools it.

How The Thermostat Can Signal The Fan To Turn On When Needed?

The radiator fan doesn’t rely on the thermostat to track the coolant’s temperature. The coolant temperature sensor performs that role.

The device tells the radiator fan when to turn on and off. It bases these decisions on the coolant temperature.

The radiator fan remains inactive when the car is moving. It only kicks in when you park because the air flowing through the radiator is insufficient. The fan is unlikely to run on a cold day.

The thermostat won’t directly turn the radiator fan on. Instead, it will ensure that a radiator fan works as expected by releasing and restricting the coolant in response to the engine’s heat.

How A Bad Thermostat Might Disrupt The Fan’s Operations?

You don’t expect the thermostat to factor into the fan’s operations directly. However, two variables may come into play:

1). Thermostat Stuck Closed

A thermostat that sticks in the closed position is dangerous. It won’t allow the coolant to flow. As a result, the engine temperature will skyrocket, boiling the coolant, elevating the pressure, and wreaking havoc on the engine and its cooling system.

The radiator fan will run continuously to counter the excess heat. Radiator fans can last 8 – 10 years under ideal circumstances. Yours will fail quickly if it runs continuously.

2). Thermostat Stuck Open

A thermostat stuck open is less offensive than a thermostat stuck closed. An open thermostat will force the engine to run cooler than usual, which attracts various consequences:

  • The engine’s rate of wear and tear will increase.
  • The fuel economy will fall.
  • The engine may lose power.
  • The engine may refuse to start on cold days because it can’t generate enough heat. This is more likely to happen in older cars with less sophisticated motor oil.

The fan won’t turn on because the temperatures won’t rise high enough to trigger the device. The coolant temperature sensor can fail. It can send the wrong readings or no readings. Without the sensor’s readings, the fan won’t turn on.

Diagnosing The Relationship Between A Bad Thermostat And A Non-Working Radiator Fan

The radiator fan is too pivotal to the cooling system for you to ignore. If you suspect a bad fan, look for the following symptoms:

  • The fan will not spin even when temperatures spike and the temperature gauge swings into the red.
  • The fan will spin slowly.
  • The fan will run continuously as opposed to intermittently.
  • The fan will make loud noises.
  • The check engine light may come on.
  • The engine will overheat.

These signs will tell you that something has gone wrong. If you still have doubts, take the following steps:

  • Start the engine and activate the AC. Adjust the settings to the maximum speed and check the fan. Is it spinning at an adequate pace?
  • Plug an OBD scanner tool into the vehicle and search for error codes. The error codes will point to the defective part.
  • If the fan seems okay, test the thermostat by placing it in hot water and determining whether it opens. You should replace a thermostat that refuses to open or close.

If you’re not sure if you should blame the thermostat or the radiator fan, you can test the fan with a multimeter to determine whether it still works:

  • Open the hood and find the fan behind the radiator.
  • Remove the motor connector and locate the terminals sending power to the motor.
  • Make sure the multimeter can read volts by adjusting the settings with the rotary switch.
  • Run the multimeter’s probes to the connector’s terminals.
  • A working fan should display readings within the vicinity of 12V. You can check the manual for the readings typically associated with your vehicle’s fan. If the fan refuses to work even though the multimeter shows the correct readings, the motor is dead.
  • The wiring system is at fault if the multimeter cannot detect a voltage.

You can also test it by connecting the car battery to the motor via jumper wires. If the motor spins, the fault lies elsewhere.

Other Causes For Radiator Fan Malfunction

  • Blown Fuse

The fuse responds to surges and short circuits. Find the fuse box and use the manual to locate the radiator fan fuse. Does it look damaged? Test it with a multimeter. A radiator fan cannot work with a blown fuse.

  • Bad Relay

Some bad relays prevent the fan from running. Others cause the fan to run continuously. Check the fuse and relay if you can’t detect a voltage with the multimeter. A defective relay may generate a clicking sound whenever the fan attempts to start.

If you’ve accessed the fuse box in search of the fuse, you might as well inspect the relays. The manufacturer keeps them in the fuse box. Make sure the replacement relays and fuses have the correct specifications.

  • Defective Sensor

A bad coolant temperature sensor will send the wrong readings to the fan. This can lead to overheating. Let the mechanic inspect and replace the sensor. The OBD scanner can identify a malfunctioning sensor.

  • Wiring Problems

Cars use wires to transmit electricity to electronic components like the sensor and motor. Those wires can disconnect, break, or sustain damage that exposes the internal conductors, leading to a short circuit.

Unfortunately, you can’t identify damaged wiring without opening the hood to inspect the engine bay. A mechanic will perform this task.

  • Damaged Motor

Test the motor by connecting the component to the car battery. A good motor will run at an adequate speed. Questionable motors will either run slowly or not at all. You should also listen for noisy bearings.

Recent Posts