Never discount the fact that the wiring could have been screwed up
badly at the OEM level by Coachmen as they built the motorhome.

 Motorhome assembly lines resemble nothing like a well-oiled Detroit
Assembly Line - the coaches are assembled in a warehouse "factory" by
three workers pushing the rolling chassis on the floor between
stations and chocking the wheels, and often assembled by semi-skilled
workers with inadequate designs and materials chosen for low price...

 Way back when, I had to partially dismantle and totally rewire a
197* Executive Class A on the Dodge chassis, as Executive Industries
(among other things) used Scotchlok tap connectors everywhere they
touched the factory harness, for both tap and butt splices...  (But
they went together fast!)  And other rank stupidity on the same level.

 The only good thing about that coach was the 413 Hemi that simply
would not die.

   --<< Bruce >>--