Could one of these faults being recirculation-related? If not..how do you diagnose when everything else works fine?

I am pretty sure if there is a problem fault with the the recirculation door operation, then it will show as a fault...it may not identify specifically a "recirculation door", but may be one of several issues grouped under a more generic fault. I really don't know. A tech II scanner (usually only dealer and high end shops have one) would tell what fault(*) the programmer is seeing. If the fault is not specific, not shown, or generic, then the FSM has many, many procedures a mechanic can do to test for ALL the possibilites in the HVAC system and the mechanic would follow the steps for "no operation" (as an example...I don't know if that is what it is called) of the recirulation mode. And many of these tests REQUIRE a Tech II scanner to perform.

Just where is this recirculation door? Is it easy to access?

I really don't know. Never had a reason to get to mine, but I am sure it is somewhere under the dash or on the firewall.

OK, looking through the FSM (for '97 H-body) last night, I didn't find a whole lot about the recirculation door.

There is no specific "fault" code identifying a problem with the "ricirc" mode. The door is driven by a vacuum operated actuator, and the vacuum supply line is the orange tube coming out of the back of the vacuum connector in the HVAC programmer. I found a crude "flow" diagram showing the actuators and doors, but never did find a specific diagram showing the actual location on where it is.

Sorry, I will look futher this weekend to see if I can find something better.

This is a graphic of the vacuum motors. I believe it'* #1 that opens the recirculate door which actually opens above the driver'* foot.

For reference the bundle of tubes in the picture is coming across the front of the heater box below (and behind) the radiator area.

So how would I go about getting to this to check out the lines and such? Glovebox removal or?

It appears the actuators are located under the dash, pretty much in the center or maybe above the gas pedal. For Bonne'* with ECC, the orange vacumm line is with 4 (or 5) other different colored vacuum lines attached to a clear connector that can be accessed by removing the black plastic panel under the dash, on the passenger -side, above where the passengers feeet would be. You may be able to follow the orange line to actuator, but it may just disappear up into the dash along with the other lines and any bundles of wires.