99 Intrigue Climate Control

[Smitty's Buick]

Greetings! I've got a problem with the 99 Intrigue that has been a problem for a couple years and I've just kind of dealt with it. It is especially pronounced in the colder winter months.

When cruising on the highway, after about an hour, the fan no longer blows out of any of the vents (vent, defrost, or floor). It gradually diminishes regardless of the temperature setting or fan speed selected. The fan is blowing as you can hear air moving inside the dash.

The car does not have dual climate control and has the 3800 engine.

I have noticed that once you stop the car and shut it off for several minutes, everything returns to normal for a period of time. I also noticed that the problem gets a little better if you turn the cruise off and vary your speed, like working through traffic or going through a town. It does not get back to 100% normal, but may go from no air movement to the equivalent of low fan speed with the fan on max.

As I said, the fan is blowing full speed as you can hear the air re-circulating inside the dash. I suspect the blend doors are not in the correct positions. I also suspect maybe a vacuum problem as it gets better by changing the engine RPM's, braking, etc..

Am I on the right track? Has anyone else encountered this problem? One more thing to add, the system does something similar in the summer with the AC on, unless the fan speed is on Max all the time.

Any help or insight is greatly appreciated.

Smitty's Buick