The dash air in my 91 still operates and is still charged with R12.
No, it will not cool the entire coach on a hot day but will keep the cockpit area comfortable.
We sometimes place a shower curtain behind the front seats to hold the cool air in with us.
If the fan blows, the dash controls work, and the damper moves from defrost to vent, repairing the ac is not really a big deal.
I saved the R12 and recharged mine during a recent radiator replacement.
Jeff & Cindy
'09 27FB Flying Cloud
'91 350 LE MH