2021 Mercedes-Benz CLA35 AMG Radiator Fan Isn't Working

Fixing the Non-Functional Radiator Fan in Your 2021 Mercedes-Benz CLA35 AMG

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Reviewed by
Devin Cabugcal
Written by RepairPal Car Genius
Updated January 14, 2025
0%
34% chance it's the
Fan Motor or Clutch
0%
28% chance it's the
Fan Relay or Fuse
0%
23% chance it's the
Temp Sensor or Fan Control Module
0%
15% chance it's
Something else
The most common reasons a 2021 Mercedes-Benz CLA35 AMG radiator fan isn't working are the fan assembly, the fan clutch, or the coolant temperature sensor.
  • Fan Motor or Clutch: A faulty fan motor or a malfunctioning fan clutch can result in inadequate cooling, causing the engine to overheat.
  • Fan Relay or Fuse: A faulty fan relay or blown fuse can prevent the cooling fan from operating, leading to engine overheating.
  • Temp Sensor or Fan Control Module: A faulty temperature sensor or fan control module can result in incorrect readings, causing the engine to overheat or the cooling fan to operate improperly.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 2021 Mercedes-Benz CLA35 AMG radiator fan isn't working?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

Over time serpentine belts stretch, crack, and the ribs that ride on the accessory pulleys being to wear smooth. A squealing noise that increases with engine speed or as engine driven accessories are turned on may be noted. The noise is caused by the belt slipping on the pulleys, insufficiently driving them. Ineffective air conditioning, a battery warning light, or intermittent power steering assist can result from this.

»MORE: Symptoms of a bad serpentine belt

The bad thermostat can cause two different sets of problems, depending on whether it's stuck open or stuck closed.

A thermostat that is stuck open can cause the engine to run colder than normal and turn on the check engine light. It may also cause poor fuel mileage and the heater to blow cool air.

A thermostat that is stuck closed will cause the vehicle to overheat. If a new thermostat doesn't resolve engine temperature problems, the cooling system needs to be checked for other issues.

» LEARN MORE: Signs of a bad thermostat, and how to fix it

When the engine coolant temperature sensor fails, it will send inaccurate information to the vehicle’s computer, causing the computer to react to false operating conditions. This will cause the engine to consume more fuel than normal, depleting fuel mileage, and causing black, sooty smoke from the engine under moderate to heavy acceleration. The check engine light will illuminate, and on-board diagnostic trouble codes may be stored for exhaust and emission system failure, fuel delivery system failure, and engine cooling system failure. Overheating may also occur, as the coolant sensor may be leaking fluid out of the engine, creating a an air pocket in the system.

When the radiator fans stop functioning properly, the engine temperature will rise. The spike in temperature will be highest when the vehicle is idling at a stop, but should subside once the vehicle begins moving again.

Additionally, the air conditioner typically won't blow as cold. This is because the air from the radiator fans also blows across the air conditioning condenser, so when the fans fail, both systems suffer.

You'll also usually see the check engine light and notice a drop in fuel economy. It's possible the fan will start making noise if it's failing, as well.

What are the steps to diagnose the non-functioning radiator fan in a 2021 Mercedes-Benz CLA35 AMG?

To effectively diagnose a non-functioning radiator fan in your 2021 Mercedes-Benz CLA35 AMG, begin with a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Start by examining the fuse associated with the radiator fan; a blown fuse is a common and easily fixable issue that can halt fan operation. If the fuse is intact, proceed to inspect the relay, as a malfunctioning relay can also prevent the fan from activating. Next, test the fan motor directly by applying power to it; if it fails to operate, the motor may need replacement. Additionally, verify the functionality of the temperature sensor, as a faulty sensor may not signal the fan to turn on when necessary. Don’t overlook the wiring and connections; ensure they are secure and undamaged, as loose or frayed wires can disrupt the fan's operation. Finally, utilize a diagnostic scanner to check for any error codes related to the cooling system, which can provide insights into specific issues affecting the fan. By following this structured diagnostic approach, you can efficiently identify and resolve the problem with your radiator fan.

What are the common problems that could cause the radiator fan to stop working in a 2021 Mercedes-Benz CLA35 AMG?

When diagnosing why the radiator fan in a 2021 Mercedes-Benz CLA35 AMG has stopped working, it's crucial to consider several common problems that could be at play. A faulty fan motor is often the primary suspect, as it can fail to spin, leading to overheating. Additionally, a blown fuse in the fan circuit can interrupt the power supply, rendering the fan inoperative. Another potential issue is a defective temperature sensor, which may fail to signal the fan to activate when the engine reaches a certain temperature, resulting in insufficient cooling. Furthermore, a worn or damaged fan belt can hinder the fan's operation, contributing to overheating concerns. Lastly, a coolant leak can lower coolant levels, adversely affecting the radiator fan's performance and overall engine cooling. Addressing these issues promptly is essential for maintaining optimal engine temperature and preventing serious damage.

How urgent is it to repair the non-working radiator fan in a 2021 Mercedes-Benz CLA35 AMG?

When it comes to the non-working radiator fan in a 2021 Mercedes-Benz CLA35 AMG, the urgency of repair cannot be overstated. The radiator fan is essential for regulating the engine's temperature, and without it functioning properly, the risk of overheating increases significantly. Overheating can lead to severe engine damage, including warped components and failed gaskets, which can result in costly repairs or even complete engine failure. Additionally, driving with a malfunctioning fan places undue stress on other parts of the cooling system, potentially leading to further complications. Therefore, it is crucial for DIY enthusiasts to prioritize the diagnosis and repair of the radiator fan to ensure the vehicle operates reliably and efficiently. Addressing this issue promptly not only safeguards the engine's health but also enhances the overall performance and longevity of the vehicle.

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