Heater blowing cold air

2005 BUICK LA CROSSE
48,000 MILES • 6 CYL • FWD • AUTOMATIC
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BRUCE_COVEY
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Have just noticed the problem, since it hasn't been that cold in Georgia. Have done some extensive research on AllData. There is no control valve for the heater core that I can find. The upper supply hose is quite hot, but the lower one is fairly cool. IF I turn the HVAC system off completely, the lower hose heats right up. As soon as I turn the system on, it tries to blow hot air for a few seconds, goes basically lukewarm, and then I notice that the lower hose goes cool. I have pulled the HVAC/ECACs fuse and done the reset procedure. As near as I can tell, the control actuators seem to be moving as I change temp settings. It is almost as if the heater core has become clogged. Could this possibly be?

Thanks
Jan 18, 2009 at 3:06 PM
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RASMATAZ
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Hello,

It does sounds like the heater core is clogged I have had people use CLR to remove the plug. Here is a guide that can help as well.

https://www.2carpros.com/articles/car-heater-not-working

Please run down this guide and report back

Cheers
Jan 18, 2009 at 3:19 PM
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DEPUTYCOLTON
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Heater problem 6 cyl Front Wheel Drive Automatic

My cars heat run me out last year. No heat now. We changed the thermostat and still no heat. The car is running fine. The blower is working normally. Could it just need the system flushed?
Dec 27, 2017 at 4:02 PM (Merged)
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STRAILER
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Hello,

This sounds like you have a temperature blend door actuator that is not working. Here are two guides that will give you an idea on how to change it.

https://www.2carpros.com/articles/replace-blend-door-motor

Here is the location for your car (below) You are going to want to replace the mode actuator I have found the dual climate actuator as well which is the right on signal controls.

Check out the diagrams (Below)

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Dec 27, 2017 at 4:02 PM (Merged)
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DEBO312
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car heater only blows cold air even if car has been stting or driven on the highway.Checked heater core hoses top one is hot, but the bottom one is cold. car does not overheat and the coolant is at the max level. the fans are blowing and there is no leakage inside of car.
Dec 27, 2017 at 4:02 PM (Merged)
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SATURNTECH9
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Sounds like you have no flow thru the heater core. In which case you can have a radiator shop do a power flush, or you can do it yourself with a hose

See the guide below on flushing a cooling system, it will help

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars
Dec 27, 2017 at 4:02 PM (Merged)
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SHANNON_PRIV
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It was the temperature blend door actuator on my car cost me $78.00 for the part.
Nov 14, 2018 at 12:38 PM