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When I start the defrost in the morning sometimes it warms up, but as you start driving it starts to blow out colder air. What could cause this?

Answers from the Automotive Experts

Colleen McGee, Driving Instructor at Americas Driving School It could be a faulty thermostat or a blockage in the hose that carries hot water to the heater or a bad head gasket

Amy Mattinat, Owner and Author at Auto Craftsmen Ltd Could be caused by a number of things: -the thermostat is working -the heater core is going bad - you have a clogged radiator. I recommend you take it to a professional auto technician for a thorough diagnosis.

Barb Petrey, President - DBK Enterprises Inc at Jiffy Lube Low coolant level or a problem with the heater control mechanism. If coolant is low, look for leaks check the passenger front floor, if its wet it has a bad heater core.

Helaine Kurot, Owner/Technician at 360 Automotive Sounds like a possible cooling system issue (coolant is not getting to/flowing through the heater core properly). If you touch both heater hoses (be careful, they should be hot) going into the firewall on the engine side, they should both be hot after the car is warmed up. if one or both are cold, you have a cooling system issue. If they are both are hot there may be a blend door control issue.

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