No Heat in Your Car Or Truck?

How to figure out why there is no heat in your car

Learn to Diagnose and Fix the Most Common Car Heater Problems.

If you have no heat in your car or truck or maybe the heater is even blowing cold air, there could be a few different causes. This article lists 4 common reasons why there is no heat in your car.

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4 Reasons There’s No Heat in Your Car

4 Causes for No Heat in Your Car

1. Low Coolant Level and/or Antifreeze in Bad Condition

The engine heats up as it runs and coolant, also known as antifreeze, circulates throughout the engine to cool it. The hot coolant travels to the heater core, where the blower motor pushes the hot air into the cabin.

If the coolant level is low

  • Coolant could be leaking
  • The radiator cap is venting or leaking
  • Internal gasket leak where the coolant is leaking into the engine as white smoke out the exhaust

If the coolant is low, you have air in the system. If air travels inside the heater core, it can decrease the temperature, which lowers the amount of heat entering the cabin.

How to Check the Coolant’s Condition

Dirty coolant drained from car. Could cause your car to have no heat
Clean coolant on the left and contaminated coolant on the right

Coolant in good condition has no contaminants. If the coolant breaks down, that can change the freeze and boiling point of the chemical. This can cause overheating or engine freeze.

Coolant can be different colors like pink, yellow, green, or red depending on the vehicle. Contaminated fluid may be a darker shade and will have contaminants in the fluid.

2. Leak Stopper

You may see coolant dripping, collecting in a puddle, or white smoke exiting the exhaust if there’s a coolant block.

Particles clogging heating system can cause your heat not to work.
Particles from a leak stopper collected on a radiator cap and in the radiator

If a part is too expensive to replace, a leak stopper can be an affordable alternative. Leak stoppers are available in a bottle or a tab. Basically, leak stoppers can find and stop leaks, but extra particles mixed into the coolant that plug the leak can remain in the coolant, and they can damage parts of the cooling system.

Eventually, the original leak will probably leak again, and the stopper will need to be flushed to remove any particles.

3. Clogged Heater Core

The heater core is located inside the passenger compartment behind the passenger side dash.

The heater core looks similar to a radiator. It has small passages the coolant flows through. The blower motor draws the hot air into the cabin, but if the core is plugged, the coolant will have trouble flowing, and the blower motor will blow colder air than usual.

Temperature Gauge to check the heater hoses if the heat is not working
Temperature Gauge

To tell if the heater core is clogged, find the heater core hoses on the firewall. Check the coolant hoses with a temperature gauge. The hoses should read for the same temperature. If the coolant hoses are at different temperatures, more than 10 degrees apart, there is likely an issue with the heater core.

4. Temperature Control Issues

Problems with the HVAC System

HVAC controls

The HVAC controls how much heat or air will enter the cabin. The blend door actuator directs air through the heater core to send warm air into the cabin or doesn’t, which lets cool airflow into the cabin depending on the setting. If the blend door actuator isn’t working, there could be an internal problem with the part or there could be an electrical issue with the part.

Problems with the Thermostat


The thermostat helps the engine reach and maintain engine operating temperature. As the coolant is reaching operating temperature, the thermostat opens up and lets the coolant flow through the rest of the system.

If the thermostat is stuck open, the coolant will keep flowing even if it’s not at the right temperature to cool the engine and thus heat up the passenger compartment. If the thermostat is stuck shut, that will cause a restriction in the cooling system, like keeping the hot coolant in the engine and the cold coolant in the heater core.

Fix Heat Not Working in Your Car

If the heat stopped working in your car, fix it with help from 1A Auto’s how-to videos that cover diagnostics and repairs for many makes and models.

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No Heat in Your Car? - Fix Common Car Heater Problems  - 1A Auto
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No Heat in Your Car? - Fix Common Car Heater Problems - 1A Auto
If the heat is not working in your car or truck and maybe the heater is blowing cold air, there could be a few different causes. This article lists 4 common reasons why there is no heat in your car.
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1A Auto
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