It works. The evaporator and condensors are so large on these motorhomes that the 134a works well. I did it and did not even "pull" the vacuum or replace the reciever dryer because of lack of time (going camping!). It will be even cooler once I replace the receiver dryer (any good chevy dealer parts counter for approx $55) and properly evacuate the system.
Rebuilt, replacement ac pump can be had at autozone or such for about $100 plus core. If the rear mount plate does not install flush on the replacement pump (likely will not), then use a grinder to modify the rear plate to fit.
Here's a poor boys trick to "evacuate" the system. Start the engine and let it get hot. Shut it down and "open" the schrader valves on the ac. Vapor, gas, moisture, or what ever in the lines will then vent. Not perfect, but...................
For 134a, target no more than 28 psi on the low side at around 1500 rpm when adding it (if you have gauge). Don't overfill or it will not cool as well. I'd stop at 70% by weight max of original r12 capacity if ya don't have a guage.
ac belt will wrap the water pump, main, power steering, and ac
belt will jump off if all pulleys are not aligned in the same plain
align pulleys or add idler pulley in front of ac pulley to solve
gee, I seem to like to rattle on here...............
regards,
Mike