03 expy - Heat not working right at high fan speeds???

[dirtrider]

I have an 03 expedition with 56K miles. I noticed my heat was not working right over the past winter. This is especially true when the vehicle is not up to full operating temperature yet. However, I don't believe it could be a heater core blockage issue. What happens is that when I have the defrost or the defrost/floor selected (front) with either the max fan or next to max I get barely any air coming out at all. The fan is obviously heard but almost no air coming out. If I then turn the temp to cold the air starts coming out. Is this a common problem? What exactly is going on? Ideas where to look, what might be broken, etc? Is it electrical or vaccuum? To be clear, if I select heat in the forward position only it seems to work fine. The controls for the rear also work fine. This is why I don't think it is a heater core issue because heat is available just almost no air flow in some positions. Is there a blend door issue with the 2003? Any quick and easy way to check the manual controls for correct functionality with an ohm meter? Any common areas of vaccuum leaks that could affect this?

 

[ELVATO]

Do you have manual controls (knobs) or the EATC (push buttons)?

 

[dirtrider]

Do you have manual controls (knobs) or the EATC (push buttons)?

manual controls. Also, I have heard of the knobs going bad so I tried changing them around and no difference. It isn't the knobs.

 

[ELVATO]

First, check to see if you engine coolant is low.

Next, bring the Expy to operating temp. Set the setting to floor, and temp to warm. Feel the two hoses going to the heater core. Are both of them hot (don't hold them for too long since they can burn you)?

 

[dirtrider]

Wanted to post again and see if anyone had any ideas. Read original post. Also, this is definitely not heater core. It gets hot just fine.

 

[GAINMOB]

im having this prob with my wifes car