2004 GMC Sierra Heater does not heat on low RPM

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07 Tucson heater blowing cold air - Hyundai Forum - Hyundai ...

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Dec 16, 2009 - I have a 2007 Tucson, when you turn on the heater it only blows hot air... Join Date: May 2005 ... a low coolant level will exhibit the first stated symptoms of no heat/low heat at idle and increased heat at cruise due to an air ...

Denlors Auto Blog » Blog Archive » Car Heater Blows Cold ...

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Oct 10, 2009 - When a car heater blows cold air, there are several possibilities that should ...... On my Dodge Neon when I turn on the heat it blows out cold air.

Heater blows only cool air...even w/ defroster on : Buick ...

repairpal.com > Problems > Buick > LeSabre
... Cadillac, Chevrolet, Chrysler, Dodge, FIAT, Ford, Geo, GMC, Honda, Hummer,Hyundai, Infiniti, Isuzu, Jaguar ... I'll turn up the temp on the dual control to get heat,

I had a 91 GMC 4.3 do the same thing. Liked to froze to ***** one winter. Found I had a air bubble (air lock) in the engine block and heater. It was a bear to get out. Finally installed back flush kit in the heater hose between engine and heater. Took cap off flush kit, pour coolant in through outlet till coolant ran through back to radiator. Replaced cap and started engine. Repeated again. Heater works as good as new. It's using the same principle as priming a gas powered water pump.

check antifreeze level add if low, and check intake heat control valve on ps side of intake if its locked shut it can be removed and a water pipe nipple put in place of it and the heater hose reconnected..if the water pump is good, it should give heat this valve should be on the intake with a heater hose connected to it..and its vacuum operated but will jam shut with age and cold weather..good luck..

It sounds like the engines thermostat is stuck open, when you idle the engine has little air over the radiator so the heater will work, but when you are driving lots of air and the engine runs cold. I am sure you just need a new thermostat.

check the coolant level in radiator. if its low it will only circulate while driving, and not while idling. May also be a bad water pump. See a professional for that.

Check coolant level. Check for heat at the heater hose going from water pump to heater core at firewall. Check to see that cable is moving coolant control valve from the closed to open position. Low mileage so it shouldn't be plugged heater core.

needs a thermastat or your low on coolant

you have a couple of problems first of all your drivers sd=ide heated heat pad is probably faulty, for your heating problem you may have to get the hvac doors recalibrated.

Blower motor resistor is most common ($20-$70) it controls the blower motor fan and speeds or fan relay fuse (usually under the hood) If it's not either then the blower itself is bad. You can pull the motor and apply 12volts to it to test, if it spins then the resistor.

check dial switch, check valve that lets water run through heater core