Furnace turning off
My 378 also has two furnaces. Only the main furnace had an issue. Sorry no photos, the modification was under warranty, but a simple mod. The main furnace had two heat ducts, both came out near each other close to the furnace. The added heat vent just taped into an existing break away on the furnace metal body. A flexible heat duct was added to the removed break away and a box section was built behind the love seat running forward with the exit at the forward end behind the love seat with the flexible heat duct inside. On my 378 the furnace and added duct work is all contained on the main slide out which is just behind the driver on the left side. If both furnaces are experiencing the same issue, you may have an LP flow problem, especially if both furnaces go out together.
Mickey & Sue Stamper
2013 GT XL 378TS
2013 Ford Escape on Landgrebe tow dolly