OK...I think we may be headed in the right direction. Since you posted in the Fleetwood Owners Club regarding a "2008 Providence" and subsequently added "40X," I think we are talking about a motorhome. A quick online search shows that Fleetwood produced a Providence 40X, so I think we have your coach pinned down to that year/make/model. In case you don't have a manual for your coach, you can find one here...
Unfortunately, as with most RV "owners manuals," it doesn't provide much specific information about actual operation of the furnace. So, another online search for "2008 Fleetwood Providence 40X furnace operation" produced a bit more information. It would appear from what I found (and, I did not check all of the search results), your furnace uses a 12V fan/blower so should operate from either 120VAC shore power or 12VDC battery power. The caveat is that furnace fans/blowers from this era eat up battery power pretty quickly. Below is a link to a post discussing this...
How to turn on furnace in fleetwood
www.popupexplorer.com
One other caution here regards the condition of the coach batteries. It sounds like the coach has been in storage for some period of time. If it was not plugged in and keeping the batteries charged, they may have been damaged. You probably should "load test" your coach batteries to determine their current condition. Obviously, bad batteries will not operate the furnace very long.
You may want to follow up with an online search for further information about the furnace operation in your specific year/make/model coach.
Good luck.
TJ