Multiple comments 13,500 BTU's may not be enough to cool it swiftly I live in a 38' Class A,, I have 30,000 BTU's and well. some days it's not enough.
What color is the Park Model? Light colors reflect sun heat better and are easier to cool
How long since you cleaned the A/C... On my rooftop units if I park near cottonwoods 4 weeks ago (I DID) the condensers quickly need cleaning (I Cleaned). NOTE Air-Xcel are easier to clean than others (Good news) and easier to inspect as well. But take a look.
Finally .. it is getting hotter out there no matter what some politicians say so you may wish to UPGRADE that unit, or add a 2nd one.
