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I know this is a weird problem but I thought i'd run it by everyone out there just in case someone else has experienced the same symptoms.......went to use the truck's(02' LB7) heater today. turned heater control knob clockwise to full heat. after truck had warmed up to operating temp i got some heat but not as much as i should have. To get any heat output i had to have knob turned to highest setting. if turned back any amount all i got was cool or cold air. a/c was not on. lots of coolant in the system. does anyone know how that heater control works? vacuum? its certainly not running a heater cable, opening or closing a valve, right off the control knob. it almost acts like something is out of adjustment. right now its all or nothing. if the knob is not turned to the highest setting there is no heat. i know that this is maybe something for a dealer to look at(hope not. ) :shrug:
 

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That sounds like the actuator door in the HVAC ducting is stuck and won't completely shut the cold side off. Theres a little electric motor that moves it. Its a common occurance in our trucks.

The HVAC controls, even the manual ones, are all electrically operated.
 

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TheBac said:
That sounds like the actuator door in the HVAC ducting is stuck and won't completely shut the cold side off. Theres a little electric motor that moves it. Its a common occurance in our trucks.

The HVAC controls, even the manual ones, are all electrically operated.
is it easy to access this motor/door?
 

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No, its not. IIRC, the door is up in the center of the HVAC. As an option, it may also be the control head, too.
 

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TheBac said:
No, its not. IIRC, the door is up in the center of the HVAC. As an option, it may also be the control head, too.
i just scored a complete set of service manuals(5 books) for my truck and in the HVAC section it appears that the air temp actuator is located on the lower section of the air box. should be able to get at it without removing too much. at least i'll be able to see if its functioning or not..........:woot:
 
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