Dometic Water Heater Trouble

[Fyrflie]

I replaced a leaking Atwood water heater with a Dometic 6 gallon gas only model. WH6-GA. Install was simple and straight forward.
Water heater worked perfect with door open but would sputter when door was closed. I added a vent to the door to allow more air and that fixed that problem. From the beginning, the flame has always come out of the flue and burned the thermal fuse and/or melted wires. I have gone thru at least 6 fuses and three wire harnesses to this point. I added some shielding around the flue and wires to keep the heat off the wire harness with limited success. This last trip, immediately following a shower, I smelt burning rubber. I traced the smell to a burnt rubber grommet on the gas line inside the water heater compartment. The gas valve also took some extreme heat and has some disfigured plastic on the gas valve solenoids. The gas orifice tube is also baked and suffered bubbled paint.
Now, when you switch on the WH, it immediately burns out the 2 amp fuse on the control board.
Weather was 55 degrees, blue skies, zero wind.
Previous troubleshooting included the following:
1- The burner tube/flue is clear. Pulled rag through it to confirm.
2- Gas pressure within spec with a dial type gauge. I have a manometer coming for further testing.
3- Confirmed a solid 12 volts to the control board
4- Getting continuity from power wire to ground wire on both solenoids. Is that correct ? I have a new gas valve assembly coming.
5- checked and replaced multiple times the ECO and Thermostat.
I’m almost ready to junk this water heater and install a Suburban model but would like to get this one to work if possible.
Anyone have any ideas on what else to check?

 

[SuwanneeDave1]

If it is new contact the manufacturer about warranty

 

[Fyrflie]

If it is new contact the manufacturer about warranty

I did. They won’t give any troubleshooting advice because of liability and they said to take it to a qualified service center for repair.

 

[Onyrlef]

I suspect a faulty gas valve. That sounds to me like an RV fire waiting to happen.

 

[Gary RV_Wizard]

I'm not familiar with whatever "improvements" Dometic may have made to the venerable Atwoods once they took over, but the gas burning outside the chamber is a key clue. Propane is extremely sensitive to air/fuel mixture and combustion outside the burner chamber means that the only place the air/fuel ratio is right is outside the burner. That means there is either a lack of air or excessive propane in the chamber. A leaky gas valve is but one possibility, since insufficient air flow into the chamber gives the exact same symptoms. So does anything that alters the flow of both/either of those so that thy don't mix properly in the chamber. That could be a faulty gasket, a hole or crack in the chamber, or something sticking out into the chamber and disrupting the mixing flow. Improper gas pressure too, but you seem to have eliminated that possibility already.

 

[Fyrflie]

I suspect a faulty gas valve. That sounds to me like an RV fire waiting to happen.

I have a new gas valve assembly coming.
As a retired firefighter, I am well aware of the fire danger. That’s what bothers me the most. This $500 boat anchor of a WH cannot be trusted. It’s crazy that it will work 3 out of 4 times normal then goes into meltdown mode.
Thanks for your reply. Very much appreciated.

 

[Fyrflie]

I'm not familiar with whatever "improvements" Dometic may have made to the venerable Atwoods once they took over, but the gas burning outside the chamber is a key clue. Propane is extremely sensitive to air/fuel mixture and combustion outside the burner chamber means that the only place the air/fuel ratio is right is outside the burner. That means there is either a lack of air or excessive propane in the chamber. A leaky gas valve is but one possibility, since insufficient air flow into the chamber gives the exact same symptoms. So does anything that alters the flow of both/either of those so that thy don't mix properly in the chamber. That could be a faulty gasket, a hole or crack in the chamber, or something sticking out into the chamber and disrupting the mixing flow. Improper gas pressure too, but you seem to have eliminated that possibility already.

Dometic made changes to the design but I hesitate to call them improvements. This WH had airflow issues out of the box. And they are well documented on the internet. They have since changed the design of their door to now include additional Louvered vents at the bottom of the door. My new door only had 3 louvers. It now has eight. The gas valve and circuit board are the only things I haven’t touched. New gas valve assembly coming. As mentioned, I have a manometer coming to double check the gas flow against my dial gauge.
Thanks for the reply.

 

[Kirk]

From the beginning, the flame has always come out of the flue and burned the thermal fuse and/or melted wires. I have gone thru at least 6 fuses and three wire harnesses to this point.

The fuses there to shut it off in the event of a flashback, as you are having, because they are dangerous. That is the root of your problems and the point at which you would have been justified to get warranty service involved. As one who was once in customer service, I am not at all surprised at the reaction by Dometic once you began to work on it. Remember that they have no way to know what your skill set is or if you are qualified to do the work. I will be interested to hear what you read with the manometer.

 

[Fyrflie]

The fuses there to shut it off in the event of a flashback, as you are having, because they are dangerous. That is the root of your problems and the point at which you would have been justified to get warranty service involved. As one who was once in customer service, I am not at all surprised at the reaction by Dometic once you began to work on it. Remember that they have no way to know what your skill set is or if you are qualified to do the work. I will be interested to hear what you read with the manometer.

I wholeheartedly agree with your response and agree with Dometics policy. However, the first flashback that happened and melted the wire harness after install by me was two weeks prior to a 10 day summer vacation. At the time, the next available service date was 3 months out. That’s why I went down the rabbit hole of DIY remedy. And to note, the problem does not occur during every operation of the WH. It might work two times or five times without issue then just when the confidence builds, it craps out. The only work I did on the unit prior to failure was to install it according to factory documents provided. The other shielding and insulation of wiring was done to try to alleviate the problems I am experiencing.
I did test the gas valve solenoids today and they test out of spec which would indicate they are possibly bad. But I believe that was due to the recent exposure to extreme heat. It still doesn’t deal with the reason the flame is coming backwards out of the burn tube.
A new gas valve assembly is enroute.
Thanks for your response.

 

[CharlesinGA]

How old is this trailer? The regulator (and what brand, or post a good pic of it) and the pigtails. And what is your elevation? (sea level, 5000 ft, etc)

How do other gas devices in the trailer? work? stove, fridge, furnace.

I very much like the Atwoods and always suggest that anyone with problems with one, even major problems, go to the expense to repair the Atwood before replacing it. The Dometic is junk, no doubt about it.

Charles

 

[Fyrflie]

How old is this trailer? The regulator (and what brand, or post a good pic of it) and the pigtails. And what is your elevation? (sea level, 5000 ft, etc)

How do other gas devices in the trailer? work? stove, fridge, furnace.

I very much like the Atwoods and always suggest that anyone with problems with one, even major problems, go to the expense to repair the Atwood before replacing it. The Dometic is junk, no doubt about it.

Charles

The RV is a 2001 Fleetwood Flair Class A Motorhome.
The original Atwood water heater had a hole in the tank along with some other corrosion issues.
All other appliances work as designed. No issues.
Unfortunately I disposed of the Atwood after the install of this Dometic.
The only line coming off of the regulator at the tank is the supply line that feeds the coach. It is hard plumbed through the belly of the coach then each appliance has a copper line feeding each individual appliance.
Elevation is Sea Level.
Thanks for your inquiry.

 

[Kirk]

It still doesn’t deal with the reason the flame is coming backwards out of the burn tube.

I have a lot of experience with Atwood water heaters as well as Suburban and slightly prefer the Atwood but I have no experience at all with the Dometic version of the Atwood. I have some experience with Dometic on a refrigerator and that leads me to find you experience with the easy to believe. They have never been supportive of the end user, only the authorized repair techs.

You are absolutely correct about the flashback as the root of the problem. To be honest, I don't know what I would have done in your situation. I wish that I could be of more help.

 

[John From Detroit]

Is there possible a "nest" inside the tube that's burning? (Shooting in the dark here). (No need for a reply).

 

[CharlesinGA]

While the water heater draws a good bit of gas, the big consumer is the furnace. You probably have a hard plumbed regulator, mounted horizontally, like this one.

If it appears original to the RV, it is way past its life limit. It might be causing your problems, hard to say. I consider a regulator over 10 years old suspect for problems.

Charles

 

[Fyrflie]

While the water heater draws a good bit of gas, the big consumer is the furnace. You probably have a hard plumbed regulator, mounted horizontally, like this one.

If it appears original to the RV, it is way past its life limit. It might be causing your problems, hard to say. I consider a regulator over 10 years old suspect for problems.

Charles

That is the style that I have. Thank you for the insight. I will check into this further.

 

[Fyrflie]

Finally got all the parts installed in my water heater debacle.
Installed a new, fully adjustable Marshall 2 stage regulator at the main tank. Initially, the outlet pressure was 12.5”WC. I adjusted it to 11”WC. I then put my gauge on the water heater gas line. Turned on the furnace and cook top. The pressure at the water heater was 10”WC so I adjusted the main regulator back to 12”WC to achieve 11”WC at the water heater.
Installed a new gas valve, igniter and Flue box. The water heater ignited immediately and worked well but sounded like a jet engine. I adjusted the gas valve down to reduce the noise a little but still maintain a nice blue flame. My next test will be to put my manometer on the gas valve to get an actual working pressure. I will update when that happens.
Thank you for everyone’s input to this point.

 

[Fyrflie]

Have not tested with the manometer but did take a short weekend trip with OK results. The WH worked as designed except for one instance where it did not light and went into lockout mode. Thinking it was the fusible link again, I checked all components for proper voltage and then turned the WH back on. Everything checked out good. It worked for the rest of the trip.

 

[John From Detroit]

There is a bit of wiggle room in that 11: One thing you need to do is observe it when it fires up a few times.... If the spark gap on the igniter (Assumes DSI) is too wide.. well that don't work well. (or too narrow for that matter) I am assuming you measured it so that's not likely and issue but check it anyway.

What are you "Observing" Does it light, go out, light, go out light go out.. That's a different problem

or does it just flat not light (Suspect gap)

 

[Fyrflie]

There is a bit of wiggle room in that 11: One thing you need to do is observe it when it fires up a few times.... If the spark gap on the igniter (Assumes DSI) is too wide.. well that don't work well. (or too narrow for that matter) I am assuming you measured it so that's not likely and issue but check it anyway.

What are you "Observing" Does it light, go out, light, go out light go out.. That's a different problem

or does it just flat not light (Suspect gap)

Thanks for the reply.
After install of new parts, I watched it light initially and let it run for about ten minutes. Then I shut it off and moved on to other projects. While camping, the first day, the WH worked as it should and cycled several times as needed to heat the water. On day two, it lit off initially with no issues, got to temp then cycled off. When it was time to cycle back on, it went into trouble mode. I confirmed the fuses were good and power was where it needed to be. I turned the WH switch on and it lit off with no problems.
I will double check the igniter gap. I looked at it initially but didn’t actually measure it.
Thanks again.

 

[CharlesinGA]

If your door does not have the extra louvers in the lower part of it, you want to either replace the door with one that does, or install vents of some sort in the door. I've seen pics of round screen wire vents snapped into holes in the door, and other similar venting setups.

This is the later style door, it also has slots for two latches, close to the corners, and the louvers in the lower center of it.

Below is the door for the conversion kit, which is wider than a standard door and has the two latch slots, you remove one latch from its place in the middle and mount it on one corner, and they give you a second latch for the other corner. It is wider to cover the filler plates that are part of the kit.

Here is the original style door that is lacking venting and has only one latch and the doors are know to peel off the RV when driving.

Here is the door hardware kit 92101

Old -Biscuit had this to say about the Dometic WH venting (On iRV2)
The Dometic WH-6GEA air intake is flawed........

Combustion air has to be pulled thru 3 open slots then DOWN thru the door latch bracket then pulled over to burner tube venturi opening and then mixed with propane flow to achieve proper air/fuel ratio
Propane has a narrow flammability range --- 2% to 9.5%
Disrupt either and no flame

Something similar to this is what I saw mentioned in various forum discussions after the Dometic WH problems appeared.

Charles