Originally Posted by Granny25
We have a 2018 Wildwood 24QXBL trailer. The water heater will light and burn 4-5 minutes and knocks off. Reset button out. switch on panel with DSL/FLT and red light. Can anyone give some advise on what would cause it to keep cutting off before water is hot?
I did not read all responses, but here are some observations:
1) Ditto on making sure there's water in the tank. You may be tripping a safety interlock to protect the hot water heater from running dry.
2) If there's water, check the burner tube for spiderwebs and so on. Ideally, remove the burner tube and orifice and blow them both out with compressed air. Also blow out the combustion chamber. A blockage might screw up combustion air and gas mixing and delivery to the burner end of the tube and trigger not just having the thing go out, but also trigger the safety interlock. If you're calling for hot water and things aren't working as they should, the safety switch may shut off the gas supply.
3) A bit harder but possible...I had this problem. My burner tube has no adjustable shutter to increase/decrease air entering the tube....and adjust the air/propane mix. My combustion would leap off the burner and then flame out. It would momentarily sounded like a jet engine...with too much air. I ended up using some foil tape to slightly reduce the air opening.
Mine did not have that, and that's where the foil tape came in. This is a "cold zone"...well away from combustion, so the tape is in no danger of burning.
Nothing wrong with that. Because it's really easy, I remove the tube entirely, and I also remove the orifice feeding the tube (the little brass thing-a-ma-bob has a hex nut built into it and comes right off), and I blow both out with air. Then I can blow out the burner chamber easily as well. Then just put it all back together. Why blow out the orifice? Well, more than once on gas grills and similar appliances - essentially the same as the hot water heater mechanism - I've encountered partially plugged orifices. Not sure what plugged them, but in one case I'm sure it was gasket material or "pipe dope" somewhere in the propane lines. When it got to the tiny pinhole orifice, it partially plugged it. If this happens with the hot water heater, it will run very "lean" (not enough propane), and the flame will keep going out from too much air...as with the shutter.
Final comment. There is an on/off control valve for the propane at the propane input of the water heater. When you throw the rocker switch to power up the hot water heater, it applies 12 volt power to the control valve and spark to the igniter, and then the thermostat on the hot water heater dictates the on and off cycle. You're dealing with a thermostat control switch, the main power switch, the spark igniter, and a 12-volt powered on/off valve to deliver propane to the orifice. You're also dealing with at least one thermocouple sensor at the burner end that confirm that there is fire...not just unburned propane saturating the space waiting to explode. Sadly, if anything is wrong in this complex system, it's unlikely to be a DIY fix for anyone but the most skilled home mechanic. The good news is that, due to the risks attendant to failures in these areas, these systems are very robust and seldom fail.
This is intended to add to, not contradict others' comments.