2021 Mercedes-Benz GLB35 AMG Radiator Fan Isn't Working

Fixing the Non-Functional Radiator Fan in 2021 Mercedes-Benz GLB35 AMG

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Reviewed by
Bo Fader
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 GLB35 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 GLB35 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 a non-functioning radiator fan in a 2021 Mercedes-Benz GLB35 AMG?

When diagnosing a non-functioning radiator fan in a 2021 Mercedes-Benz GLB35 AMG, it's crucial to follow a methodical approach that emphasizes simpler checks before tackling more complex issues. Start by inspecting the fuse linked to the radiator fan, as a blown fuse is a common and straightforward problem to fix. If the fuse is in good condition, move on to the relay that controls the fan; a faulty relay can prevent the fan from operating altogether. Next, test the fan motor by applying power directly to it; if it does not spin, the motor may need to be replaced. It's also important to check the temperature sensor, which is essential for activating the fan; ensure it is functioning properly and sending the correct signals. Additionally, examine the wiring and connections for any loose or damaged components that could disrupt the fan's operation. Finally, utilizing a diagnostic scanner to check for error codes can help identify any specific issues affecting the fan system. By adhering to this structured diagnostic approach, you can effectively pinpoint and resolve the problem with the radiator fan.

What are the common problems that could cause the radiator fan to stop working in a 2021 Mercedes-Benz GLB35 AMG?

When diagnosing why the radiator fan in a 2021 Mercedes-Benz GLB35 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, effectively shutting down the fan. Another potential issue is a defective temperature sensor, which may fail to signal the fan to activate when the engine reaches a certain temperature. Worn or damaged fan blades can also hinder airflow, preventing the fan from functioning properly. Lastly, electrical issues such as loose wiring or corroded terminals can disrupt the fan's operation. Addressing these problems promptly is essential to avoid engine overheating and ensure the longevity of your vehicle. Regular maintenance and inspections can help you catch these issues early, allowing for effective DIY repairs.

How urgent is it to repair the non-functioning radiator fan in a 2021 Mercedes-Benz GLB35 AMG?

When it comes to the radiator fan in your 2021 Mercedes-Benz GLB35 AMG, urgency is key. A malfunctioning fan can lead to severe overheating, which poses a significant risk to your engine's health. Without proper cooling, the engine can reach dangerous temperatures, resulting in warped cylinder heads or blown head gaskets, both of which can lead to costly repairs. Additionally, the performance of your vehicle's air conditioning system may suffer, as it relies on effective engine cooling. Ignoring the signs of a failing radiator fan not only jeopardizes your engine but can also lead to extensive damage that could have been easily avoided with timely repairs. Therefore, if you notice any issues with your radiator fan, it is crucial to address them immediately to safeguard your vehicle's performance and longevity.

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