GMC Sierra 2500 Radiator Fan Isn't Working

Diagnosing the Causes of a Non-Functional Radiator Fan in Your GMC Sierra 2500 and How to Fix It

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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 GMC Sierra 2500 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 GMC Sierra 2500 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 first indication of a defective fan clutch is a healthy cooling system that runs below or above the normal temperature range. This is due to the fan running too fast or too slow. Also, a seized cooling fan will cause a loud roaring fan noise from under the hood every time the accelerator is pressed, and the engine will feel as if it lacks power. In this situation it would be very difficult to turn the engine cooling fan by hand, of course when the vehicle is off. Finally, if the clutch fails the fan will either turn very slowly, and not respond well to engine speed.

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.

Troubleshooting Radiator Fan Issues in a GMC Sierra 2500

When troubleshooting radiator fan issues in a GMC Sierra 2500, it's essential to adopt a systematic diagnostic approach that begins with the simplest solutions before progressing to more complex assessments. Start by checking the fuse associated with the radiator fan; a blown fuse is a common and easily fixable issue that can often be overlooked. If the fuse is intact, inspect the wiring harness for any signs of damage or wear, as faulty wiring can disrupt the fan's operation. Next, evaluate the electrical system, including components that activate the fan, such as the air conditioning and engine cooling systems, to ensure they are functioning correctly. Testing the relays for both high and low-speed operations is crucial, as malfunctioning relays can prevent the fan from working as intended. If you encounter any error codes related to fan speed, such as Code 0495, addressing these codes promptly is vital to prevent further complications. Lastly, understanding the role of the Powertrain Control Module (PCM) in regulating the fan's operation can provide deeper insights into potential issues. By following this structured approach, you can effectively diagnose and resolve radiator fan problems, ensuring your GMC Sierra 2500 maintains optimal cooling performance.

How to Diagnose and Fix a Non-Working Radiator Fan in a GMC Sierra 2500?

When tackling the issue of a non-working radiator fan in your GMC Sierra 2500, it's essential to understand the common problems that could be at play. One frequent culprit is a blown fuse, which can disrupt the power supply to the fan. If the fuse is intact, the next step is to inspect the fan assembly for any visible damage or malfunction. Additionally, the fan clutch should be examined to ensure it engages properly; a faulty clutch can prevent the fan from operating as intended. Another critical component to check is the coolant temperature sensor, as inaccurate readings can lead to improper fan operation. Wiring issues are also common, so inspect the harness for any signs of wear or damage that could impede power delivery. If the fan runs continuously or fails to turn off, consider potential problems with the engine or thermostat, as these can affect the fan's behavior. Lastly, if your check engine light is illuminated, consulting diagnostic codes can provide valuable insights into the underlying issues. By being aware of these common problems, you can effectively diagnose and address the malfunctioning radiator fan, ensuring your vehicle's cooling system remains efficient.

Why is the Radiator Fan Not Working in a GMC Sierra 2500?

When the radiator fan in your GMC Sierra 2500 is not functioning properly, it is crucial to address the issue promptly to avoid severe consequences. A malfunctioning radiator fan can lead to overheating, which may cause extensive engine damage and costly repairs. Additionally, if the fan fails to operate, it can result in inadequate airflow through the radiator, compromising the vehicle's cooling system and potentially leading to engine failure. Ignoring symptoms such as fluctuating fan speeds or constant operation can exacerbate the problem, increasing the risk of overheating and creating unsafe driving conditions. Therefore, it is essential to diagnose and resolve any issues with the radiator fan as soon as they arise, ensuring the longevity of your vehicle and maintaining safe driving conditions.

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GMC Sierra 2500 Radiator Fan Not Working: Causes & Solutions