1998 Dodge Durango Heater control issue?
Heater blows hot air fine until...I select vent setting with blower on high (I can hear the blower running on high), but I get very little air movement thru the vents but it blows fine on defrost or floor. If I turn the temp down just a bit I get cold outside air blowing thru the vent on the vent setting, if I keep the same temp setting but select defrost or floor it works fine and blows correct warm temp air. I think the previous owner must have installed a new heater core just from the tell tail signs of missing dash hardware and broken plastic brackets. Anyone have any ideas?
Comments
A common problem on some vehicles is a bad blend door or actuator for it which controls the flow of air past the heater core or to the various vents in the dash or floor depending on the heater switch selections.
My guess is that the vacuum switching valve in the heater controls is bad or one of the blend doors /actuators is bad or installed incorrectly during the previous heater core repairs. Some people have had issues with aftermarket heater cores being the wrong dimensions and not allowing the blend door to operate correctly.
http://www.dodgetalk.com/forums/showthread.php?t=1...
There is one blend door to divert airflow through the heater core or A/C evaporator...or just outside air... and a couple other doors to divert airflow to the dash, floor or defroster vents.
I would pickup a Chilton or Haynes shop manual ...parts stores carry them and some libraries...which will show the blend door positions/HVAC ducting and ways to check them. There could also be an issue with the dash heater controls/ switches not sending the right vacuum signal to open or close doors...check that as well. Listen for any hissing noises which indicate a vacuum leak and check the vacuum lines under the hood as well. A bad check valve in the main vacuum line from the engine or vacuum reservoir can cause variations in blend door/heater control operation.
http://www.mopartech.net/showthread.php?t=5670
2001 Dodge Durango Heater Control Valve