Why does my car heater only work when the car is moving?

When your vehicle is in motion and driving down the road, then engine coolant temperature tends to get hotter on the engine before it gets to the radiator, so the heater will naturally heat up more when driving around.

Why does my car’s heater blows cold air when stopped?

A dirty or clogged heater radiator



The heater’s radiator clogs over time making it harder for the coolant to pass through its bearings, leading to slightly warm air or completely cold air blown at idle.

Why does my car heater not work when idling?

Two things come to mind, defective or wrong thermostat or low coolant level. The engine makes very little heat when idling, and if the thermostat does not close, the engine coolant temperature may drop low enough that you’ll get no heat from the heater core.

Why does my heat stop working when I stop moving?

A heater can stop working for a number of reasons, including: A low antifreeze/water level in the radiator due to a leak in the cooling system. A bad thermostat that isn’t allowing the engine to properly warm up. A blower fan that isn’t working properly.

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Why does my heat only work when I accelerating?

Check Heater Control Valve



It allows hotter water to flow only partly when the power and RPM load are higher than when you accelerate, and otherwise not enough. … The circulation air tests the cold and warm air “mix” until it is released from the air, which results in very little hot air from the heater ducts.

Why does my heater get cold when idling?

You may have trapped air in the cooling system or the heater core may be partially plugged up. Engine coolant is delivered to the heater core through two heater hoses.

How do you know if your thermostat is bad in your car?

Symptoms of a Failing Car Thermostat

  1. The temperature gauge reads high and the engine overheats.
  2. The temperature changes erratically.
  3. The vehicle’s coolant leaks around the thermostat or under the vehicle.

How do I know if my heater core is clogged?

Heater core failure symptoms

  1. Weak or no airflow.
  2. Cold air (not warm) coming through the vents when the heater is on.
  3. Coolant leakage visible inside the cabin or a damp smell.

What are the symptoms of a bad heater core?

Five Signs Your Car’s Heater Core Is Going Bad

  • Fog Inside Your Car. Two things could be going on if you have fog inside your car. …
  • Sweet Smells in the Car. The sweet smell in your car might not be your perfume or the donuts you’re taking to work. …
  • Constant Engine Coolant Loss. …
  • Cold Air in the Cabin. …
  • Cold Cabin/Hot Engine.
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Why does my car heater only work when I hit the gas?

It’s caused when your coolant gets low. Fix your leak and bleed the coolant system. Or you can check this theory by filling and bleeding the coolant system now. If it works, it will be ok until the coolant system gets low and causes the air bubble again.

Encyclopedia auto repair