Could help to know the Model Year of the Ford Chassis. Your "1995 Coach" might be on a 1994 Ford Chassis. If it came with an original Owner Manual, the Year on that is probably right. Better, the Build Date on the Ford sticker in the door frame. For example, our "2003 Jayco" is on an E450 where Ford's label says "Date 03/02" making it a 2002 chassis. Parts and wiring could be different.
The diagrams say the Starter "Relay" is in the Left side of the Engine Compartment. On ours, the Relay is on the Passenger Side, all but hidden by the Battery. It looks like two massive posts (From Battery and To Starter) and a single small terminal that a connector simply pushes onto. That wire should go HOT when you turn the Key to Start. If you put +12 to that little terminal on the Relay, it should close and operate the Starter.
That's a correction to my earlier reference to the Yellow Wire. If it's onto that little Push Terminal, it's the one that tells the Relay to Power the Starter. I had thought there was another wire, on the Battery Post of the Relay, that was the power feed to the rest of the chassis.
We've recently seen Ford OEM battery cables that lost contact within the terminals. Looked good but didn't work...
If it's killing "House" (also called "Coach") batteries, as MEX said, that's an additional system, additional problem. If you aren't disconnecting that Battery in Storage, some parasitic drain (like LPG detector) could be running it down. If you leave it plugged into shore power in storage, your Converter/Charger could be boiling the battery.
