Is Your Truck’s Heater Not Working? Here are Some Common Reasons Why

Oct 9, 2018 | Blog

You’re miserable the whole time you’re on the road.


Because the heater in your truck isn’t working! That means you have to drive 45 minutes, or an entire trip, in a freezing cabin.

The first step to fixing your heating system is finding out what’s wrong with it. We’ve put this guide together to help diagnose why your heater’s not working.

So, stay tuned as we walk you through some of the most common heater problems.

Understanding Your Truck’s Heater

Your heating system is actually just your cooling system. It uses the same coolant, but instead of cooling it down, it heats it up.

Here’s how it works.

As you drive your truck, the engine gets warm. This heats the coolant, and the cooling system has to circulate it through the radiator to bring the temperature back down.

When you turn on your heater, the coolant flows through the heater core inside your dashboard. This allows the hot air to blow through your vents and heat up your cabin.

Why Is My Heater Not Working?

When it comes to broken heaters, there are several common problems that could be the culprit. Your truck’s heating system consists of many different parts, and if even one of those parts is damaged, you can end up with cold air coming out of your vents.

We’ve put together a quick explanation of each of these problems.

If you’re trying to figure out what’s wrong with your heater, there’s a good chance it has to do with something on this list.

1. You Don’t Have Enough Coolant

If your truck doesn’t have enough coolant, your heating system can’t send it to the heater core.

It’s normal for cold air to blow out of your vents for the first few minutes after you turn on the heater. But it should warm up fast. If it doesn’t, your coolant level might be low.

You can fix this by filling up your engine coolant. Keep an eye on the coolant levels each time you open the hood. Trucks that are going through a lot of coolant in a short period of time might indicate you have a leak. And a coolant leak can end up with your engine overheating — leading to more costly repairs.

2. Your Thermostat Is Stuck or Malfunctioning

A stuck or malfunctioning thermostat can’t control the coolant flow through the radiator. That means the coolant will keep circulating through the radiator and stay cold.

You can tell your thermostat isn’t working if it’s stuck in the same place no matter what you do or how long the engine has been running. Thermostats are cheap, and you can install a new one without a lot of effort.

3. Your Heating Controls Are Malfunctioning

Your heating problems might be the simple result of broken controls. After pressing the same buttons again and again over the years, they can fail.

This is a solution you might consider if you can’t find anything else.

4. Your Heater Core Is Getting Old

Think of your heater core as a much smaller radiator sitting in your dashboard. As the coolant runs through the passageways, the heater core takes the heat and sends it through your truck’s vents.

These passageways are small. When you don’t replace your coolant, it can carry debris that causes those passages to rust or clog. A clogged passage prevents any warm coolant from getting through.

You might be able to clear out your heater core passages by flushing them. If that doesn’t work, you’ll need to replace your heater core altogether.

5. You Have a Leak

Coolant travels through several parts of your engine. A leak from any of those places can prevent your heating system from working properly. You should look for a leak in your water pump and hoses.

If your radiator starts leaking, your coolant levels will get too low. You should never ignore a radiator leak. A mechanic can repair the radiator if the damage isn’t bad. You can also repair a leak by installing a new radiator.

6. Your Heater Valve Is Stuck

The valves in your heater core open to let warm air into the vehicle. If the valves are closed, the warm air doesn’t make it to the truck’s cabin.

Sometimes these valves get stuck on the closed position and this could be a simple fix.

7. Your Coolant Hoses Have Deteriorated

As your truck ages, the coolant hoses get worn down. This can lead to clogs or loose clamps. If you’re struggling to find a coolant leak, these hoses should be one of the places you check.

You should always replace old coolant hoses, along with any other hoses, when you notice any wear or leaks.

How Much Does It Cost to Repair My Truck’s Heater?

Because there are so many reasons that your heater might not be working, it’s almost impossible to say how much repairs will cost.

If your truck only needs minor fixes, you might pay as little as $300. But in some cases, you might have to shell out a lot more to fix your heating system.

You can get several estimates in your search for the best price and choose the most economical option. Just make sure the technician is reputable.

Preventing Heater Problems in the Future

The best way to avoid pricey repairs is by keeping your heater well-maintained. Have a technician give your heating system regular inspections to ensure each separate part is working properly.

So next time you’re wondering, “why exactly is my heater not working?” remember, we can help you figure that out. If you need heavy-duty or light-duty diesel truck repairs call Overdrive today.