Question (You can tell if you are outside the MH when it tries to light) does it succeed in lighting or not?
Mine acted rather weird a few years back.. I had to reset the gap on the points,, It worked great after that for about a year.. This is the 2nd DSI furnace I have worked on (The other was my parent's oil fired house furnace) and on both of them the points were set farther apart than the manual stated they should be.. Re-setting the gap fixed the home unit 100% far as I know (Parents both gone now) it's still working.. .The RV's lasted a year after re-setting. Then it developed a new problem
With this new problem it would light 3 times, It actually lit, I could hear the change in tone and feel the heat.. But it would not stay lit, It shut down
Turned out to be a bad control board (More in a sec)
Other suspects are the thermocouple (Which may also be an ignition point) make sure it's clean and operating (If you need I can tell you how to test but .. Well, better if you already know)
Or the connecting wire,, Check for rusted/corrorded connections.
The mother board.
I went with a Dinosaur board replacement
OEM 250 dollars plus S&H
Dino 108 in my hand
Better built (The quality is impressive) and from what I can tell better designed as well.. I have a theory as to what killed my board and Dino Seems to share my opinion as they included a protection device on their board.