ScottG, after owning the trailer (bought new) 3.5 years with only moderate AC use, a capacitor failed. Dometic's genius designers made this a non-replaceable part, so the entire unit must be replaced.
We were sitting in an RV park with the AC running on day two of a long trip, when I smelled that "electrical fire" smell. The fan continued to work, but no cold air. As far as I know, there was no cause other than poor design, or poor workmanship at the factory. I use a surge protector, so I doubt there was a problem with the power.
I sent a long email to Dometic, hoping they would offer something toward repair since this was a no-moving-part item that shouldn't have failed with so little age or use.
Of course, their response was basically "too bad".