My RV's wiper motor is weak, or maybe the linkages are sticking badly. If the windshield is wet enough to lubricate the blades, that helps. If the wind catches them it'll start going if it's otherwise refusing to move. Today with just very light rain, they didn't want to move at all at first until the wind helped them. Then it was stuck again when I got back until I got out and moved the arm by hand.
It looks like the metal part of the dash can come out by just removing philips screws to access the wiper motor, since it's in the dash, not outside under the hood. I'm going to check Dollar Tree for spray lithium grease and try to lube up the linkages to see if it helps, since the motor is about $70.
I might have to spring for the motor after the new year, when I'm going to be in a city where I drive after dark every night, often with rain. Normally I don't because I'm usually in places I don't know well. But I know that city so I don't mind it. Plus I only drive a few miles after dark, mostly in very well lit places. This past winter/early spring when I was there, I just dealt with the poorly working wipers, even at night.
Unless I can figure out a way to take it apart and lube it. It looks like it comes apart fairly easily based on the photos online. I might try that before replacing, since the core charge at O'Reilly is only $1. (Why even bother having a $1 core charge?!) If I tear it up trying to fix it, it's no big money loss.