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I have a 2004 GMC Duramax; It has heater and the ac problems. If the heater is on you cant shut it off and turn the ac on. And Vise versa but works once in a while. Or sometimes you have to shut the truck off for a while and it works. And the heat doesn't get hot and the ac doesn't get cold.

Posted by Bryan Moehrke on


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John Tunney

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The actuator motor for the ac/heat door is broken. best bet is to unplug ac fuse in winter and disconnect heater hose in summer

Posted on Nov 04, 2013


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  • 1 Answer

SOURCE: Heater not dispersing hot air

There ia an actuator that controls the flap to change from hot to cold. You have to pull the bottom part of the dash and the whole blower motor housing. The part you are looking for is located just behind the radio and has an arm that goes into the heater core line. That is the piece you need. Its around $165 dollars and a dealer only part. And hope you have someone that can do it because mitsubishi charges over $500 in labor.

Posted on Sep 19, 2008


Marvin Thornbrue

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SOURCE: 2005 GMC Sierra 1500 - heater blows, but only cold air

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.

Posted on Jan 07, 2010

Testimonial: "You were absolutely correct. Low coolant level. Put in some 50/50 and we're nice and toasty now, but need to find out why coolant was so low. Thanks."


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SOURCE: 2004 mercury mountaineer.heat problem When turning

2004 mercury mountaineer.heat problem
When turning ac knob to heat clicking sound like door opening and closing repeatedly sounds and air blows cold instead of hot.

Posted on Nov 11, 2010

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