'97 Tahoe LT. Dash Vents Blow Weak

[wirlybird]

I've always thought the airflow out of the dash vents is a little weak. Figured it is just that way. For clarity I mean the vents that face you and not defrost or feet vents!!
Recently had the A/C fixed, new compressor, and the repair guy mentioned weak airflow out the dash vents. He said every Tahoe of this vintage he has worked on has weak air out of the vents.

When I got home I fired up the '97 K3500 and checked it and sure enough the vents blow much better.

All of the controls work properly in the Tahoe. It is the original blower motor.
The defrost blows hard and especially on the passenger side. Drivers is a bit weaker.
The "feet" position also blows hard.

One thing I did find is that when the Tahoe is in the "vent" position I still get airflow out of the driver side defrost. Not a lot but some from the far left end of the defrost vent. The K3500 doesn't do this.

 

[GoToGuy]

Check the module that drives airflow selection is moving ? Then drop the fan clean the evaporator and heat exchanger area, there could be , dog hair, fuzz, dead bugs, corn, plant matter, god knows what get sucked into the fan area, the exchangers act like filter screens, and must be checked at some point. Get clogged with debris just like a radiator. Checked your radiator lately, dead bugs, rocks, birds , rags, hay...?

 

[wirlybird]

Check the module that drives airflow selection is moving ? Then drop the fan clean the evaporator and heat exchanger area, there could be , dog hair, fuzz, dead bugs, corn, plant matter, god knows what get sucked into the fan area, the exchangers act like filter screens, and must be checked at some point. Get clogged with debris just like a radiator. Checked your radiator lately, dead bugs, rocks, birds , rags, hay...?

Airflow changes with the controls and seems ok. You can hear it move. The defrost if powerful as is the feet/lower vent. It is just the vents that face you. The flow is ok but not super strong. Definitely weaker than the truck is.
I'm assuming that having a little bit coming out of the left most side of the defrost vent is a sign. However, the side window defrost vents always blow also. Figured it was normal to have a little defrost action going.

External radiator and condenser are clear.

Will pull the fan motor and see what it's like.

 

[GoToGuy]

Since you say it's weak in one selected zone, I would check to see if the valve/ flap that controls zone selection. If you don't have service manuals, at the top in search box enter " service manuals " for the PDF link . The HVAC chapter diagnosis is easy to follow.

 

[wirlybird]

Thanks. I plan to check the motor that drives the "zone" selection as I see it is an issue when I google. Or is one possible issue.
Since my truck does not blow air when on the "vent" setting I think it's logical to assume either the door doesn't close or move all the way or doesn't seal right.
Hopefully it will be an easy one.