Up to '94 on the CV/GM, the optional automatic temperature control (ATC) had no digital display...therefore no onboard diagnostics are available. EATC didn't debut on a CV/GM until '95.
What applies to '93-94s with the same ATC setup will apply to a '92.
If the blend door isn't moving, chances are that the nylon gears inside the electric blend door actuator (BDA) or the wiring to the BDA itself has failed.
The dash does not have to be completely removed to access the BDA, but it must be loosened from the firewall. Note that the BDA is visible from the glove compartment opening so the wiring to it can be inspected without removing the dash.
Hope this helps