Now THAT may be the fault of the motorhome modifications. But the seat itself did not do anything wrong.
I trust NOTHING untested. Your replacement switch may or may not be better than the original. After driving several hours with the lights on, do as I suggested above and grasp the stem of the switch with your fingers. Is it hot? It shouldn't be. And that ends with a PERIOD. No sense dealing with it if it's not a problem.
I do not give a **** what kind of switch it is or where it is IT SHOULD NEVER GET HOT TO THE TOUCH.
And as far as Ford is concerned, the first ignition amplifiers I found clamped to the side of distributors was insulated with clear silicone grease. Ford electrical STUPIDITY. I replaced the modules, roughed up the aluminum surfaces with 220 grit sandpaper and used the proper heat sinking material ZINC OXIDE.
And then there was Ford's 2nd generation alternators. A pair of 25 amp rated push on terminals to carry up to 75 amps of IAR alternator load. Result? FIRES! Not a dozen, not hundreds but THOUSANDS. Ford sleazed out of a general recall.
Transpo Electronics made a fortune modifying alternator rectifiers and changing to a standard stud which fit a freshly drilled hole in the case.
But the 2G, and the headlight switch problem is history. Hopefully a majority of that era's engineers are as well. Fear not, GM and MoPar have their electrical nightmares history as well. Line-em-up. Nissan, Toyota, Schultzwagen and let us not forget the Volvo with wire insulation rotting off under the dash after eight years.
I've said it for years I would have lasted mere minutes in a corporate environment before I went to prison. You can't cure stupid.