Have RV Questions? Ask an RV Mechanic Online.
Has it been sitting idle for some time? IF SO, the flapper discs on the gas valve may be "stuck" and not allowing the LP to pass. It comes from moisture in the LP, usually from the tank not being purged properly when new. It may be a defective coil on the valve as well. These are what is called "redundant' valves and if one coil is bad they won't work. Those can be checked with an ohm meter to see if that is the case. Be sure you have good LP working pressure at the regulator. That should be adjusted at least once a year. Those would be the most common problems based on what you shared. The top can be removed on the valve to clean the discs if it is narrowed down to that. You may want a mobile tech to come and assist as there are some springs in there. It can be kind of tricky to do, but cheaper by far than a new valve. Once I get to my computer I can give you a manual on this at no extra charge. Hope this proves helpful here. Please get back to me if you need more later as all follow ups are included in our fee.
Check your connections. And if you have a 12 VDC test light you can test this pretty easily. I will be at my computer soon and can send you a manual. A test light is about $5 and easy to use and you can track this down. When it stopped, the water must have been up to temp or not?
Low input DC voltage can do this. And if the LP pressure hasn't been checked in the last year, it should be. Low LP pressure causes the flame to burn lean and flash when it starts up. That can cook the safety fuse and leave the board without power.
I am adding a link to the Atwood Service Manual for you. Print out a copy as there is a lot of great information in there. Please get back to me if you need more and I will make a phone chat offer for you in case you feel that would be more productive. Many of our customers prefer this. http://bryantrv.com/docs2/docs/atwoodwaterheater.pdf
Just checking back to see if you need more input from me on this issue or were you able to get it resolved with the manual I provided here?
Just checking back in to see if you need more help with sorting this out? Thanks!