Bellingham Auto Repair

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My Car Heater is Blowing Cold Air

My car heater is blowing cold air. What can I do?

MWhy is your car heater blowing cold air when you want hot? Is the engine at the proper operating temperature? Does your car’s engine have the proper amount of coolant and what condition is the coolant? Is your climate control system working correctly? How about your cabin air filter. Replace dirty cabin air filters.

Hot coolant flow makes the cabin warm.

Car Heater

Your car’s heater operates by circulating engine coolant through a heat exchanger called a heater core. The heat exchanger lives in the dash. The climate control channels air across the heat exchanger. If the engine is cold, there will be no heat in the heat exchanger to transfer into the cabin. If the engine coolant is low there may not be enough hot coolant circulating through the heat exchanger. For the climate control to heat the cabin there must be enough hot coolant flowing through

You may have noticed semi trucks on the freeway with a zipper over the radiator. Many semis have louvers built into the radiator assembly to close off the cold air going through the radiator. Large diesel engines don’t produce enough heat to keep the engine at the proper operating temperature. When the engine runs cold it destroys fuel economy, creates excess wear and of course keeps the heater from heating.

A stuck thermostat in your car’s engine can cause the engine to run cold and so affect your climate control.

Both the heat exchanger and the evaporator live in a climate control air box made up of various plastic doors and a blower motor housing. Depending on the sophistication of your car’s climate control the doors channeling the air to meet temperature demands of the passengers may be operated by cables or by electric, “stepper” motors operated by a climate control computer. If hot coolant is circulating through the heat exchanger but no air is being channeled across the hot heat exchanger into the cabin the heater won’t heat the cabin.

Part of the reason we recommend regular coolant replacement is to avoid expensive heat exchanger replacement. When coolant no longer circulates through the heat exchanger the heater will not work. In the same way if air can not circulate across the heater you will also have no heat.

Start with the simple things.

To address car heater problems first make sure your radiator coolant is topped off and your cabin air filter is not plugged. Never place “stop leak” or other quick fixes from a can into your cooling system. Make sure your engine is at its proper operating temperature. If you are still having a no heat problem give us a call at Master Auto Tech. 360733-3043

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Auto service