Chevy Avalanche Fan Keeps Running (6 Reasons)

So you’ve turned off your Chevrolet Avalanche, but you can hear the radiator fan whirring. Obviously, it’s still running.

It’s a real issue most car owners can relate to. This article will answer why your Chevy Avalanche fan keeps running and how you can solve that.

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6 Common Reasons Your Chevy Avalanche Fan Keeps On Running

The most common causes for your Chevy Avalanche fan to continue running even when you’ve turned off the engine are related to faults found in the fan relay, the temperature sensors, the ECU unit, the high-pressure switch, the coolant liquid, or the thermostat.

The work of your Chevy Avalanche radiator fan is to maintain a cool temperature in the engine or under the hood.

When you shut off the engine, the electric fan will keep running until the engine is cool, so you will hear the fan noise seconds after turning off the car.

But, when it runs uncontrollably, it can lead to wear in the fan component and battery drain.

Tip: Use an OBD-II scanner tool to check if any Diagnostic Trouble Code (DTC) is showing up.

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Here’s why your Chevy Avalanche fan stays on continuously:

1. Faulty Fan Relay

Your fan motor relay acts as a switch that turns off or on the cooling operation according to the engine temperature limit.

It controls the entire action of your Chevrolet fan; hence, a fault in it will result in it running even with the engine off.

This is described as a relay short, and the consequence is a power trip.

2. Faulty Temperature Sensors

The sensor monitors the temperature produced by the thermostat and/or the coolant. They are responsible for giving off the feedback your vehicle fan needs.

If the temperature sensors are bad, they send the wrong result to the ECU, and what is the result? Your vehicle’s fan will keep running even if the engine is completely shut down.

3. Bad ECU Unit

Your Chevy’s engine control unit signals the fan when to turn off or keep running. A defective ECU will result in the fan not knowing when to stop running.

4. Low Coolant Level

The car coolant is the liquid that removes heat from the radiator. The lower the coolant level, the less effective it’ll be.

Technically, a little coolant will dissipate little heat, and the temperature sensor will signal the ECU to turn on the fan and cool the engine. As a result, the fan runs wild.

5. Faulty High-Pressure Switch

Always check your high-pressure switch even if it looks brand new. The high-pressure switch is usually located under the air box.

6. Bad Thermostat

Another component in the cooling system that can cause your radiator fan to continue spinning even when the engine is off is a bad thermostat.

How To Fix Your Chevy Avalanche Fan That Stays On

Solving your Chevy fan’s problem is easy because the likely causes are few. Here are some solutions to why the Chevy Avalanche fan won’t turn off even when the engine is powered off:

1. Replace Fan Relay

The way to determine if the fault is from the fan relay is by replacing it, running it, and determining if the problem persists.

If the problem does not continue, you should replace the fan relay.

The average cost range for replacing a Radiator Fan Relay of a Chevrolet Avalanche falls between $39 and $46.

2. Replace the Temperature Sensor

Often, the problem lies in the temperature sensors. Unplug the sensors and check if the fan will stop. If it stops, then the sensors are faulty and need replacement.

You can not repair an engine coolant temperature sensor.

Here is a breakdown of replacement costs by model:

ModelEngine Temperature Sensor Replacement Cost*
Avalanchebetween $629 and $675
Avalanche 1500between $579 and $623
Avalanche 2500between $1,051 and $1,116
*The average cost is calculated by adding the cost of labor and the price of the parts

3. Check the ECU Unit

Because your car ECU unit is responsible for the temperature limit setting and informing the fan relay when to turn off and on. If your fan runs continuously, you should check the ECU unit for fault and replace it if that is the reason.

Component repair is not always easy because it comprises wires and sensors; a replacement is the best course of action.

The ECU costs between $500 and $2000 for parts and labor. You can negotiate a fair price, but that depends on the technician.

4. Add Fresh Coolant

If the coolant levels are low, top it up by pouring fresh ones to the correct level. Don’t do this when your engine is still hot, or you’ll risk damaging the engine.


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Your Chevy Avalanche uses the Dex-Cool compatible antifreeze. Obviously, a coolant problem has the cheapest solution on the list.

5. Replace the High-Pressure Switch

Replace your high-pressure switch with a new one. You don’t need to remove the freon. The switch just comes off, and you won’t lose any freon.


A/C High-Pressure Switch

Check the description or use the year/make/model drop down bar and interchangeable part numbers to confirm the compatibility before purchase.

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6. Replace the Thermostat

Replace your thermostat with a new OEM one. Clear the CEL (Checking Engine Light) before turning on the engine again.

Here is a breakdown of thermostat replacement costs by model:

ModelThermostat Replacement Cost*
Avalanchebetween $708 and $740
Avalanche 1500between $629 and $643
Avalanche 2500between $823 and $841
*The average cost is calculated by adding the cost of labor and the price of the parts

Frequently Asked Questions

Can Low Coolant Cause The Fan To Stay On?

Yes, a low coolant can cause your car’s fan to stay on. The coolant removes heat from the car engine maintaining optimal temperatures within the system. When there isn’t enough of it, the engine heats up and the ECU will instruct the fan to stay on.

Is It Okay For Fan To Run After Turning Off Engine?

It’s absolutely OK. The coolant absorbs heat after operating your engine and has to be cooled. When you turn off the engine, the car’s computer detects that the radiator has reached a higher temperature and should be cooled further. In order to reduce the temperature of the coolant, the fan will run for a few minutes.

How Do I Know If My Cooling Fan Relay Is Bad?

You can know if your cooling fan relay is bad if you are experiencing any of these signs. Engine overheating, cooling fan not working, continuous running of the cooling fan, engine check light on, the air conditioner’s poor performance, harsh fan noise, and relay swapping.

Why Does The Cooling Fan Come On When The Engine Is Cold?

The cooling fan comes on when your engine is cold because the car’s climate control switch is on. The fan control unit will take the signal from the climate control and activate the fan as required. It could also be a fault in the fan relay that prevents the fan from getting the turn-off signal.


Fan noise is normal for even our laptops, but it shouldn’t continue after you’ve shut down the system.

If your Chevrolet Avalanche fan won’t turn off even after running several minutes after you shut down the engine, you should check the ECU, the coolant level, the fan relay, and the temperature sensors.

Additionally, if everything else is fine, check the A/C high-pressure switch and lastly, the thermostat.

The solution to these problems is replacing the defaulting component. But make sure you hire a good mechanic for all replacements.

Your Chevy Avalanche will thank you by lasting longer.