What to do When Your Car Heater is Not Working

July 6th, 2018 by

Cold person inside car with thermometer
Car heater not working? It’s a relatively common problem, and it makes sense to consider a few quick fixes before bringing it in to the shop.

How Does Your Car Heater Work?

Radiator fluid runs through the engine and becomes hot. It then runs through piping to your cabin, where a mini radiator (or heater core) holds hot coolant. A fan blows over your heater core and directs warm air into the cabin.

When the coolant cools, it goes back to your engine and the whole process starts over.

Why is the Heater Not Working?

Even if you’re missing a little coolant from the system, the engine can still run at the correct operating temperature. The first thing to be affected will be the heater core — since it is higher than the engine, there might not be enough coolant to reach it.

Check coolant levels by inspecting:

  • Radiator: Check your owner’s manual to find out how. You’ll basically remove the cap to check that the fluid is topped up.
  • Coolant Reservoir: If there isn’t any coolant, you should add some. Don’t go over the “Cool Fill Line.”

Now go for a ride until the engine heats up and the dial is between C and H. You should have heat in the car. If not, it’s usually because the water pump isn’t working.

Why is the Heater Not Blowing Hot Air?

In some cases, the problem might have nothing to do with coolant:

  • If your blower only works on the highest setting, your blower motor control module probably needs to be changed.
  • If the fan isn’t working, you probably need to have the blower motor fixed or changed.
  • If the air coming through isn’t hot, the heater core is probably clogged.

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