Need Help Diagnosing Water Heater Issue

[demijac]

Our water heater works perfectly when we have shore power.

When boondocking, it will only light if the exterior vent is open. When the vent is closed, it won't light period - if the vent is open, it lights up immediately. After it lights up and we close the exterior vent, it will stay lit until the water is heated (usually about 20 to 30 minutes) and then automatically go out as it is supposed to. However, it will not restart automatically when the water cools as it is supposed to. The end result is no hot water by morning. We get this same behavior when boondocking at both high altitude and low altitude campgrounds so it is not an altitude issue.

QUESTION: Why does it light when we have shore power and when boondocking, only light if the exterior vent is open?

QUESTION: Have you experienced this in your rig? If so, what was the fix?

Thank you for your ideas.

[cwf]

That is weird... I can’t imagine...

[Al and Missy]

What exterior vent are you talking about? My water heater doesn't have a vent, only a cover that is closed with a twist clamp. The only thing I could think of is weak batteries that can't fire the piezo igniter and shore power charging the batteries gives higher voltage. Maybe having the door open blows the air/gas mixture closer to the spark so it will ignite. Check to make sure the burner tube isn't clogged with spider nests or debris.

I'm reaching here.....

Al

[TG Twinkie]

Where is this "exterior vent"?

[djarrett]

I'm suspecting that he means he must open the water heater access panel on the outside for it to light.
You may check to see if the heat diverter that ports the excess heat and vabors has gotten knocked free. Ours was that way after we got it home. Had to realign all the tabs and "set" them with a screw driver and hammer tap.

Other than that possibility, ... I can't imagine.

[lyleapgmc]

Originally Posted by Al and Missy

The only thing I could think of is weak batteries that can't fire the piezo igniter and shore power charging the batteries gives higher voltage.

I'm reaching here.....

Al

Piezo igniters do not require any external power such as a battery.

[Al and Missy]

Originally Posted by lyleapgmc

Piezo igniters do not require any external power such as a battery.

Then I guess I misspoke when I said Piezo. On reflection, Piezo requires a mechanical impact. I guess is it some kind of electronic ignition.

Al

[VaTravelers]

If I am on shore power mine will be heated by the heating element. When I am dry camping, I use propane to heat the water. I am not sure what vent the OP is talking about. Mine just has an external door with vent holes cut into the door. I was having a problem with mine (2017 Serenity) a couple of months back. It would not light on propane electronically. I could light it manually, and it would heat the water and then cut off as it should, but it would not relight when the water cooled. So after a lot of trouble shooting it turns out it was the circuit board. Once that was replaced, it works perfectly.

[demijac]

yes .... the exterior cover with a twist clamp - also with a small vent in the cover.

[demijac]

It's the cover on the side of the trailer secured by a twist clamp. The cover also has a small vent and a peep hole to see if the flame is ignited.

[demijac]

Sounds like a promising angle. Not sure what a heat diverter is. Do you mind sending a pic? Thanks.

[demijac]

Thanks VaTravelers .... another promising angle. When you were boondocking, did you ever try starting the water heater with the exterior cover open? If so, did it light?

[David Logue]

Weak Batteries would be the first thing to check, also the igniter and venting area under the water heater panel

[VaTravelers]

Originally Posted by demijac

Thanks VaTravelers .... another promising angle. When you were boondocking, did you ever try starting the water heater with the exterior cover open? If so, did it light?

Yes we did and it did not ignite. It ignited when I manually lighted it. I actually replaced the igniter and did pretty extensive trouble shooting. I ordered a new circuit board from the internet and it was defective. The circuit board provided by the Dometic repair fixed the problem. If you look through the postings you’ll find quite a few posters who had the same problem, that ended up being the circuit board.