Glen,
I certainly don't mean to sound sarcastic but, it took four pages for someone to ask you what kind of coach, engine, chassis, and more. Many of the remedies that were suggested only apply to rigs with gas engines. Some applied to diesels. Now that you've stated your type of engine etc. Along with this post, I'm sending along a couple of pictures of the starting system on our coach. It's an '04 Itasca Horizon, 36GD with the C-7 330HP CAT.
Now, in those pics, you'll see the starting system relay and, remote mount solenoid. There's also a 100 amp fuse and, a secondary relay. All of which play a part in starting this beast. Now, here's a point. I have no idea if your DIESEL rig has anywhere near, the same type of system or not. If so, you'll need to find it and check it out. If not, well you can disregard this entire post.
But, our rig is 10 years old and, you'll see the kind of condition I found that starting system in, by accident when I was doing some other maintenance and repairs. So, while I had good access to it, I rebuilt it. But, your rig MAY have something very similar. Good luck.
Scott
