AC Problem

[Obelix]

I am not sure what the problem is but that's why I am throwing it out here. The air coming from the vents seem to flutter like the fans are losing power and it does that off and on. It still blows out cold air so I have no idea what it might be. I was trying to be proactive in getting it fixed before it goes down the crapper and didn't think it would involve the temperature resistors so with much hesitation I took it to to the International dealership here in town as I have no clue about AC units. Well after a new blower motor, linear pwr module resistor and $400 less in my pocket, the problem is still not fixed. They wanted to keep it all day tomorrow to try and figure it out so before I ended up with a brand new AC system I got my truck out of there. Any ideas on what the problem might be?