Welcome to iRV2.
If your Tradewinds is built on a Freightliner chassis , then the start signal from the ignition switch, does not go directly to the starter, there is a relay involved.
I have had this relay fail twice in five years of owning my Freightliner chassis Newmar coach.
My relay is mounted on a plate , passenger side frame rail behind the wheels, and looks like the picture below ( left hand item) and the pdf file is for the Freightliner P/N along with cross references.
Also if your on a Freightliner the other 2 pdf's could help with your gauge problems.
I've lost track of the relay spec sheet.
I'll re-post as soon as I find it.