2008 Mercedes-Benz CLS550 Radiator Fan Isn't Working

Radiator fan not working in 2008 Mercedes-Benz CLS550: causes and solutions

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Reviewed by
Andrew Hajjar
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 2008 Mercedes-Benz CLS550 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 2008 Mercedes-Benz CLS550 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 initial diagnostic steps to take when the radiator fan isn't working on a 2008 Mercedes-Benz CLS550?

When faced with a non-functioning radiator fan in a 2008 Mercedes-Benz CLS550, it's essential to adopt a systematic diagnostic approach. Begin by checking the fuse associated with the radiator fan, as a blown fuse is a straightforward and common issue that can easily be resolved. If the fuse is intact, the next step is to inspect the relay that controls the fan; a malfunctioning relay can prevent the fan from receiving power. Following this, test the radiator fan motor itself to ensure it operates correctly, as a defective motor will not spin even if all other components are functioning. Additionally, verify the temperature sensor's operation, since a faulty sensor may fail to signal the fan to activate when necessary. It's also crucial to examine the wiring and connections for any signs of damage or loose connections that could disrupt the fan's operation. Finally, using a diagnostic scanner to check for error codes can provide further insights into any underlying issues within the cooling system. By methodically following these steps, you can effectively diagnose and address the problem with your radiator fan.

What are the common causes for the radiator fan not working in a 2008 Mercedes-Benz CLS550?

When dealing with a non-functioning radiator fan in a 2008 Mercedes-Benz CLS550, it's essential to understand the common problems that could be at play. One of the primary culprits is a faulty fan motor, which can prevent the fan from operating and adequately cooling the radiator. Additionally, a blown fuse can disrupt the electrical flow to the fan, rendering it inoperative; checking and replacing this fuse is a straightforward task for DIYers. Another potential issue is a malfunctioning temperature sensor, which may fail to signal the fan to activate when the engine reaches a certain temperature. Wiring problems, such as damaged or corroded connections, can also impede the fan's functionality, making it crucial to inspect the wiring for any visible issues. Lastly, low coolant levels can affect the fan's operation, as the fan relies on the coolant to help regulate engine temperature. By systematically checking these areas, you can effectively diagnose and resolve the issue of a non-working radiator fan, ensuring your vehicle runs smoothly and efficiently.

How urgent is it to repair the non-working radiator fan in a 2008 Mercedes-Benz CLS550 to prevent engine overheating?

When it comes to the radiator fan in your 2008 Mercedes-Benz CLS550, urgency cannot be overstated. A malfunctioning radiator fan directly impacts your engine's ability to regulate temperature, which is vital for optimal performance. If the fan fails, the engine is at a heightened risk of overheating, leading to severe consequences such as warped cylinder heads or blown gaskets, which can result in expensive repairs. Additionally, an overheating engine can cause a noticeable drop in performance and increased fuel consumption, further complicating your driving experience. Therefore, addressing the issue promptly is not just about maintaining comfort; it’s about safeguarding your vehicle’s longevity and preventing costly damage. If you notice any signs of fan failure, such as unusual engine temperatures or warning lights, it’s crucial to take action immediately to ensure your CLS550 remains in peak condition.

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2008 Mercedes-Benz CLS550 Radiator Fan Troubleshooting Guide