Your semi truck has a climate control system to ensure that you have a comfortable ride regardless of the outside weather conditions. One of the crucial parts of this climate control system is the heater core. In this article, we’ll learn how the heater core in your semi truck functions and how you can maintain it for optimal performance.

What Is a Heater Core?

The heater core is part of a vehicle’s HVAC system that heats the cabin and defrosts the windshield when needed. The primary function of this component is to provide heat to the driver’s cabin. In short, it helps the HVAC system blow out warm air when it’s increasingly cold outside, especially during winter. 


Sample of a premium aftermarket heater core

For semi trucks, the heater core is located inside the vehicle’s HVAC box. This box is uusally found on the inside or outside of the firewall. The heater core will typically sit along side the evaporator in the HVAC box and often looks like a mini radiator. 

How Does a Heater Core Work on a Semi Truck?

The heater core uses the engine’s coolant to increase the temperature within a semi truck’s cabin. There are typically either manual or electronic shut off valves that allow you to shut off of coolant in the heater core during warmer months and turn it back on during cooler months.

When the heater is turned on, the engine allows the hot coolant (usually betwenn 165 degrees to 185 degrees) to flow to the heater core. Your HVAC system’s blower motor will force air across the fins of the heater psuing warm air into the cab of the truck.

Keep Your Heater Core Working Optimally

Like other parts of the HVAC system, the heater core is affected by age, corrosion, and blockage. We will talk more about these three issues below. To keep your heater core working optimally be sure to inspect and clean it on a yearly basis. 


Sample of a damaged truck heater core. (Source: CarTreatments.com)

1. Age

The heater core may not be able to regulate the temperature of the hot coolant due to age. Its several components are prone to wear-and-tear and continuous use may cause a reduction of its overall functionality.

2. Corrosion

The heater core is exposed to liquid, steam, moisture, and mildew, which speeds up rusting. When certain areas of the component are corroded, it becomes susceptible to a coolant leak which will eventually lead to complete failure.

3. Blcokage

This is probably the biggest issue that we see on trucks is the heater core and evaporator can become completely block with dirt. The wet conditions inside your HVAC box mixed with the dust from the outside of your truck tends to turn heater cores and evaporators into an adobe brick not allowing air to pass through the fins of either the heater core or evaporator. 

All the above issues can be mostly avoided by inspecting and cleaning your heater core and evaporator on a yearly bases. Unfortunately, there is little that can be done about age ad corrosion, but it is better to replace the heater core proactively when you don’t need it than to have to replace it in the middle of winter when you can’t live without it.

What Are the Common Signs of a Faulty Heater Core?

You can easily tell that your heater core isn’t functioning at its best when it doesn’t provide enough heat, there’s fogging in your windows, or a sweet smell in your cab. To know when you need to get your heater core checked, let’s take a closer look at these signs:

1. Lack of Heat

When you’ve turned on your heater and your HVAC system is still blowing off cold air, then it means your heater core might have some problems. 

2. Excessive Fogging

The fog on your semi truck’s windows is caused by moisture buildup inside your car. It’s the heater core’s job to regulate this moisture to avoid fog. When your HVAC unit can’t produce ample warm air, thick fog might appear on your windows and windshield. While it can easily be wiped off, it can prevent you from seeing the road. 

3. Sweet Smell in the Cabin

The engine coolant leaking from your AC system may produce a sweet smell around your cabin. It may smell fragrant, but it poses a great risk to your health. If this sweet smell is combined with steam from your HVAC vent, then you might need to get your heater core checked.

How Can You Properly Maintain the Heater Core of a Semi Truck?

To maintain the full functionality of your heater core, you should use the right coolant, clean the air filter regularly, clean the heater core yearly, and replace an old unit when needed. Let’s discuss each of these maintenance tips:


A good aftermarket heater core for semi trucks

Use the Right Coolant

Using the right coolant ensures that your heater core and radiator will work properly. Also, it’s very important to fill and maintain your coolant at the proper level. If you have a question on the correct amount of fluid, reach out to your dealer and they can provide the amount.

Clean the Air Filter

A dirty air filter can restrict both cold and warm air from properly circulating in your semi truck’s cab. Furthermore, it can damage the blower motor by making it work excessively. By regularly cleaning the air filter, you can ensure that the warm air produced by the heater core is sufficient to cover the cabin and defog the windows. Many Kenworth trucks didn’t come with an air filter right out of the factory. We are now offering a fresh air filter kit for Kenworth W900, T800, T600, etc.

Clean the Heater Core

As mentioned before, your heater core and evaporator requires yearly maintainance in order to operate optimumly. 

Replace the Heater Core of an Old Semi Truck

If regular flushing and other troubleshooting methods won’t work, then it’s time to replace the heater core. Fortunately, there are truck parts providers that sell premium aftermarket heater cores compatible with most semi trucks and conventional cab trucks.

Get a Stainless HVAC Box

Trucks that operate in the salt belt are susceptible to more corrosion issues with their HVAC components. This is especially true for HVAC units designed with metal boxes or shells. To avoid this, it’s best to get a premium stainless HVAC box to ensure the optimal functionality of your HVAC system regardless of the weather.

Keep Yourself Warm and Comfortable on Every Ride with a Premium Heater Core

Truck drivers, among all drivers, know how hard it is to drive through cold weather. Fortunately, your semi truck comes with climate control to give you warmth on these kinds of days. Stay comfortable while on the road with our line of high-quality aftermarket heater cores. Same dimensions and performance of an OEM but at a better price.

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