98 Park Ave. cabin air circulation problem
 

The mid-level cabin vent doesn't open at all. The defrost works pretty well but almost no air coming for A/C or heater.Blower motor and A/C working fine. I disassembled partially the air duct under the dash and observed that the air flap doesn't move when changing the "Air Flow" selector through its range. Does anyone know where the fuse for that flap actuator would be? If I have to replace this it looks like a fairly major project (steering wheel and dash removal) as well as the blower box. Thank you in advance for any help you may be able to give me.

Systems were designed to go to defrost mode in default mode. If no control is available for whatever reason , result is defrost mode.

Good chance blend door actuator is in need of replacement. Not too difficult to do if you the have time and patience. Two small bolts hold the actuator in place behind the glove box on the top of the duct work. If you get the replacement actuator you can see how everything is assembled and that makes it a lot easier to plan your moves.

Thank you for your quick reply. There appears to be 3 separate actuators, with 2 on the driver's side and 1 one on the passenger side next to the glove box as you said. I can see two doors higher up closer to the dash vents those appear to be operated by one actuator on either side of the heater box. The 3rd actuator is lower down on the driver side and appears to operate 2 flaps that close off the bottom ducts that warm your legs.I was playing around with the control buttons and observing the doors from underneath.I tried every setting there is and none of the doors ever move. At times I can hear a clicking and an intermittent noise depending on the buttons I push but I can't tell which one (or more) its coming from.

98 Park Avenue cabin air circulation problems
 

I eventually found out that in order for those blend doors to move, I have to have the engine running. Not just have the key in the "On" position. Anyway, the doors actually move, so they work. But erratically enough that it appears the problem is with the HVAC control module behind the glove box. Delco part no. 16238774.I don't know if anyone but the dealer can test that. I haven't checked at the dealer but according to some internet posts I've read it looks like they cost 500-600 dollars. At this point that's about what VMR website says the car is worth. I might try to find a used part. The car has 175,000 miles on it.

You might try a salvage yard. The price should be a lot less and even if it works for 1 or 2 seasons you hopefully got your money's worth.

98 Park Avenue cabin air circulation problems
 

You are right. The GM dealer informed me yesterday that the part has been discontinued. Thanks for your help and God bless your day!