If you're still in Pahrump, I've used two places for mechanical/chassis maintenance and repair and they both do chassis air conditioning repair.
Leroy's Auto-Air is at the corner of Basin and Barney. It's a small shop run by Leroy and his wife Pam. They routinely work on both cars and motorhomes. They definitely do RV chassis air conditioning repair.
Yahoo reviews
RV Service Review
(they recently had a bad review on YP but it sounds rather bogus to me)
Another place I've used for more heavy-duty chassis work is Rod Paulson's in the far north end of town on Leslie Street (4590 N Leslie St). They work on truck, bus, and RV chassis work but also RV air conditioning and other RV house related repairs also ...i.e. slides, furnace, water heater, etc. I personally haven't used them for RV a/c work but they do RV a/c repairs too (see their website
HERE)
RV Service Review
If you are no longer in Pahrump and need a good place in Vegas, let me know and I can give you several good places I've used there too.