A constantly running radiator fan in your 2015 GMC Sierra can be incredibly frustrating – a noisy annoyance that drains your battery and potentially indicates a more serious underlying problem. This comprehensive guide will walk you through the common causes of a perpetually active fan and provide troubleshooting steps to help you get your truck back to its normal, quiet operation.
Understanding Your 2015 GMC Sierra's Cooling System
Before diving into troubleshooting, it's crucial to understand how your truck's cooling system works. The radiator fan is controlled by several factors, including:
- Engine Coolant Temperature: The primary trigger. When the engine coolant gets too hot, the fan engages to dissipate heat.
- Air Conditioning (AC) System: The fan often runs when the AC is on to help cool the condenser.
- Electronic Control Module (ECM): The ECM monitors various sensors and dictates when the fan should turn on and off.
- Fan Relays and Fuses: These components control the electrical power to the fan motor.
Diagnosing the Problem: Why Your Fan Won't Turn Off
Several issues can cause your 2015 GMC Sierra's radiator fan to stay on constantly. Let's examine the most likely culprits:
1. Faulty Coolant Temperature Sensor (CTS)
The CTS is a crucial component that monitors engine coolant temperature. A malfunctioning CTS can send inaccurate readings to the ECM, leading the ECM to believe the engine is overheating, even when it isn't. This often results in the fan running continuously.
Troubleshooting: A scan tool can read the CTS's temperature readings. Compare the readings to the actual engine temperature (using an infrared thermometer) to determine if the sensor is providing accurate information. A faulty sensor will need replacement.
2. Problem with the Radiator Fan Module (RFM)
The RFM controls the fan's speed and operation. A failing RFM can cause the fan to run constantly or malfunction in other ways.
Troubleshooting: Inspect the RFM for any visible damage or corrosion. Replacing the RFM might be necessary if the module is defective. A professional mechanic will likely need a scan tool to test its functionality.
3. Low Coolant Level
Insufficient coolant can trigger the overheating protection system, causing the fan to run continuously.
Troubleshooting: Check your coolant level in the overflow tank. If it's low, carefully add coolant to the appropriate level (refer to your owner's manual). Never open a hot radiator cap. If the coolant level continues to drop, you might have a leak somewhere in the cooling system.
4. Failing Fan Relay or Blown Fuse
A malfunctioning relay or a blown fuse will prevent the fan from turning off.
Troubleshooting: Inspect the relevant fuses and relays. Refer to your owner's manual for their locations and amperage ratings. Replace any blown fuses with the correct amperage. If a relay is faulty, replace it as well.
5. Wiring Issues
Damaged or shorted wiring within the cooling system's electrical circuit can also cause the fan to stay on.
Troubleshooting: Carefully inspect all wiring related to the radiator fan, looking for any signs of damage, corrosion, or loose connections. Repair or replace any damaged wires. This often requires a multimeter to check for continuity and voltage.
6. Faulty Radiator Fan Motor
Finally, the problem may lie with the fan motor itself. A seized or malfunctioning fan motor could cause it to remain on, even after the engine has cooled.
Troubleshooting: While visually inspecting the fan motor for damage is important, determining if it’s the root cause often requires testing with specialized equipment.
When to Seek Professional Help
If you're uncomfortable performing the troubleshooting steps above or if the problem persists after trying these solutions, it's best to take your 2015 GMC Sierra to a qualified mechanic. A professional can diagnose the issue accurately and perform the necessary repairs safely and efficiently. A constantly running fan can lead to further damage if left unaddressed.
Remember to always consult your owner's manual for specific information regarding your vehicle's cooling system. Safety first – never work on a hot engine.
