Water heater

[Flightmedic]

So my 2015 Bullet UL is getting a huge makeover due to water damage. So she’s been sitting a little over a year. Did a local test run last night and water heater didn’t make hot water on electric. I switched to LP and it started working. I woke up this morning and had HOT water. Got a shower and it ran out within less than a minute. No way it was 6 gal. The control panel had a red light on the fault. I turned water heater off and light went out.
Where do I begin to troubleshoot this? All other appliances worked 100%.
Thanks

 

[chuckster57]

Make sure it’s not in bypass mode. The fault light means the gas didn’t ignite. If it’s been sitting for a long time, I would start by blowing out all the passages, and then try it again. You can turn it on and you should be able to go out and watch/listen for ignition and gas valve opening. Brand/model number?

 

[Viper02]

Looks like you have the Atwood WH.. if so this is the service manual that will help you..

https://techsupport.pdxrvwholesale.com/wp-content/uploads/2018/09/Atwood-Master-Water-Heater-Manual.pdf

 

[Stu Norman]

On my Hideout, there is a small on/off switch on the water heater. It is located below one of the pipes on the water heater and can be hard to see if you're standing at the rear of the trailer looking down at the water heater. If that switch is off your heater will not work on electric mode.I went through a few days of Campground troubleshooting until another camper showed me the switch.