Reasons Your Car Heater is Blowing Cold Air

Your car heater is blowing cold air, it’s freezing outside, but you have to make it to work. This is a common issue that can wreck your day, make your boss mad, and your ride home even worse.

During a cold winter, you need to have your car warm up to melt the ice and snow before you leave home. If your car heat is blowing cold air then this will become difficult.

There are a few components to your vehicle’s heating system, so let’s explain what’s possibly causing the problem.

First, Check Your Coolant…

When you turn the heater on, some of your coolant starts flowing to the heater core from the engine. It takes a while for the heater to start blowing hot air because it has to warm up as the engine warms up the coolant.

For some vehicles, the engine and coolant will warm up faster, allowing the heater to blow hot air. However, if your vehicle warms up and the air never gets warm, then you might be low on coolant.

Pop the hood, check if the coolant is low, and top-up as needed. When the coolant gets too low the engine won’t be able to divert coolant to the heater core. This is why many mechanics recommend checking your coolant often during the cold months.

Signs of a Faulty Heater Core

Heater cores are a little more tricky to diagnose, as they’re situated behind your dashboard. Instead, you will need to look for the signs of a faulty heater core.

But wait, what is a heater core? Well, it’s part of your cooling system, and it looks like a smaller radiator made of brass or aluminum tubing. It has tubing and fans, so warm coolant from the engine can pass through the tubing and the fans can push the heat into your vehicle.

So, what goes wrong with heater cores that can cause them to stop functioning properly? They leak. Heater cores leak, and most of the time you will notice a damp spot under your dashboard when this happens.

Signs of a bad heater core include:

  • Smelling coolant inside your car
  • Little to no heat (cold air blowing out in the winter)
  • Coolant fogging up your windows (very dangerous, fix immediately)
  • Engine running hot
  • Constantly having to top-up your coolant

Smelling coolant is bad, but when there’s enough coolant in the air to fog up your windows then it becomes very dangerous. That means there was enough coolant leaking into the car to cause a mist over your windows, which is bad to breathe and also makes it difficult to see.

A Faulty Thermostat

Coolant is only sent over to the engine when the thermostat sends a signal that the engine is getting hot. If the thermostat never sends that signal, then it will never open and let coolant in the engine. The engine warms up the coolant, sending it to the heater core so your car can heat up during the winter.

Diagnosing and replacing a faulty thermostat is simple. If the temperature gauge in your car reads very high and it looks like the engine is overheating after only letting the car run for 10-15 minutes, then the thermostat is likely the culprit.

Another sign of a faulty thermostat can be found by looking at the temperature gauge on your car. This time, you will notice the temperature change erratically and fluctuate from low to high and vice versa. This is a very common symptom.

Something else you can do is locate your thermostat housing and check for leaks. Check for leaks all over while you’re at it.

Replacing a thermostat is relatively easy on most vehicles, and the actual part is inexpensive.

Fix Your Car Heater

Never ignore a problem related to the cooling system of your vehicle! Even if you live in Florida where it never snows! If your heater isn’t working then there could be something wrong with your car, causing it to lose coolant. Make sure your engine isn’t overheating, as that can cause more severe and expensive problems.

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