Hot water heater dead in the water!

[TBone55]

We finally are on our twice delayed (thanks COVID) trip from NY to Utah & AZ.
Everything has been working great until we boondocked at Natural Bridges for the Dark Skies.

The hot water heater would try to start: gas would come out but no visible spark.
I tried to manually light it and it would run only for a few seconds then go out.
I decreased the space between the contacts to improve the spark - no good.
Yes, we have LP gas. I checked all of the electrical connections and now it doesn't even send gas out when I flip the switch inside. No blown fuses.

Now we are in Bluff, UT with full hook ups and the electric water heat doesn't work as well! Motherboard???

I'm pissed. This is a 2018 23CB that I am still calling new! Any ideas????

Thanks,
Tim

[Hans627]

Happy to hear that you are finally getting to make your trip.

The computer board in the water heater is the usual suspect. They are know to fail at the most inopportune time.

Many people carry a spare in their parts kit. Maybe someone has a spare. The same water heater is used in many different brands of RV's.

And if you are a member of the AS Club you could check for the local unit and maybe make a few phone calls to members and they might be able to point you in a specific direction.

[TBone55]

Thanks Hans627
I guess I diagnosed it correctly. Will check into local chapters.

Thanks for the input!

[TBone55]

So the 2018 Dometic elec/gas water heater died on our trip from NY to Utah. I diagnosed it to be the mother board. Ordered one online, had it delivered to a campground, pick it up and installed it today. Turned on the gas switch first, it fired for a second then nothing. Tried the electric - usually hear a high pitched tone when it is running - but nothing. I'm now in Moab, a long way from New York. Does anyone have any other ides to try? Thanks! PS - My wife is with me!

[GCinSC2]

Tbone55,

Have you confirmed gas supply and flow by using a different gas appliance and letting it run for a short time.

Tank is not set for bypass, correct?

Suggest two people for this. One operates the GAS switch, one is at the water heater with its door open and observing stuff.

Inside person turns water heater on.

Outside person, what do you hear?
Ignitor spark noise?
Gas solenoid valve clicks?

What else do you see, smell or observe?

Disconnect and reconnect plug to control board.

Just for grins, a pic of the unit with door open just showing all the stuff.

Gary

[TBone55]

Hi Gary,
I tested all you suggested. Gas is working elsewhere, the bypass is not on - but the water heater worked great for the first two weeks of our trip (both gas and electric.). I replaced the circuit board with a new one and when my wife threw the gas switch, it fired up for a couple of seconds then quit. I haven't been able to do that again. I used to get a high pitch sound when the electric side was working. But nothing now - can't smell gas coming through either. Here's some pix:

[GCinSC2]

Tbone55

Do you have a multimeter ?

When you test fired did you hear ignitor sparking?

Keep feedback coming.

Still have the old board? What did it do, same as current situation?

And the air shutter looks pretty wide open. I did search the Atwood water heater docs I have service and training. There was no mention of altitude adjustment required. Mine is about 1/3 open yours looks about 2/3 open. I can get details in a bit for initial setting of shutter.

Gary

[GCinSC2]

The air shutter initial setting is 1/4 open per Atwood manuals. This is a snapshot of the Direct Spark Ignition sequence of operation.

Previously posted was a water heater playlist from Darren's My RV Works YT channel, he has covered Atwood diagnostics in several of them. And on his mobile My RV Works website he has made available hundreds of factory manuals. Pick resources, category, make and download.

https://myrvworks.com/manuals/

Multimeter?

Gary

[TBone55]

Hi Gary,

Thanks for your research! I got a hold of an RV tech guy in town who stopped by this morning. He agreed the motherboard was bad because it was not creating a spark. But the new board wasn't working either. We had weird voltage readings off the wiring harness and found one questionable wire that had been spliced that the safety thermocouple was wired to. Once we fixed that it fired up!

Back in hot water! And on my wife's birthday! Life is good.

Thanks again for the help!

Tim

[GCinSC2]

Tim,

Good news, now where are you taking her for her B-day dinner?

Any chance for a pic of the wiring fix?

Gary

[TBone55]

The culprit!

[GCinSC2]

Tim,

Interesting. I've looked and didn't see that butt connector in your earlier pics.

That "thing" in the plastic tube melts when exposed to high temp like a heater that is running but the flame is coming OUT rathe than thru the U tube. It melts, circuit opens and damage should be minimized. I did see an SOB on time that had tell tale black streaks out the top of the WH compartment.

I carry an extra melt fuse, ECO, T-stat sensor in my spares.

Thanks for the follow up. It can help someone else.

Gary