Need help troubleshooting HW heater

[Johnynorthland]

Hi all, my Dometic hot water heater model GC6AA-10E will not stay lit on LP, will work on electric.

If I stick my grill lighter in the burn a tube, I can light the hot water heater but then the gas valve shut off after a few seconds. Im very familiar with home hot water heaters and HVAC, I’ve changed many a thermocouple. To me this seems to be a similar problem but I’ve never worked on these units.

I had the rig washed yesterday, by a professional who’s washed it in the past for me. I had a discussion with him about not spraying water directly into any vents or grates before he started. And he understood fully. . I’m just hoping that this is a coincidence.

We rarely use the hot water heater on LP. I shut it off yesterday before it was washed. So forgetting to turn it back on all day, I switched it to LP knowing that’s the quickest way to get it hot water.


I’ve done the following;

tested the 2 amp fuse in the circuit board, it’s good.

Disassembled and checked the burner tube for obstructions, it’s very clean.

I removed and checked the water heater thermal cut off, and checked for continuity with an Ohm meter, it’s good. Is it ok to jump out the thermal cut off, just to further test it?

The one thing I noticed is the electronic igniter does not spark, could this be the issue? When I light the burner with a lighter it light but shuts off after a few seconds. I can repeat this 3 times and then I have to do a reset by switching LP off/on again.

What senses that there’s a flame to keep the gas valve open, is it the second probe on the igniter?


Any help appreciated

[TWP723]

Sounds like a regulator. It'll shut the gas off if it detects a leak. Does everything else work ok?

[craigav]

Check to verify any parts I share here to make sure they apply to yours.

Generally speaking, I like to know what is broken prior to purchasing new parts, however sometimes I go a different route.

I would replace the electrode that you asked about because on the Atwood and likely other models the sparker electrode is also the flame sensor. If it failed completely then there would be no spark or flame sensor so the unit will try 3 times then quit trying until you do a reset, that is for safety reasons. With my comment here, I would certainly check all of the WH connections and in particular to the igniter\sensor first to it to make sure it is a completely dry connection and connected well prior to replacement.
https://www.amazon.com/dp/B07CNHLH6N...osi&th=1&psc=1

Second, while I would do what I mentioned first, the next likely issue would be with the igniter circuit board itself. Especially if it looks burned, or doesn't click when trying to turn the heater on with lpg (maybe they are solid state and don't click anymore though). Again as above, be sure to check all the wires coming into and out of the board and elsewhere to make sure that you are not dealing with a poor connection.
https://www.amazon.com/Atwood-91365-.../dp/B019COT1HC

This link is for a supplier of the boards that many people state are the most reliable replacement boards. https://www.dinosaurelectronics.com/Ignitor_boards.htm

An additional thought, while I would simply replace the igniter/sensor first if no other visible symptoms are seen, I would consider getting a board now as with the chip and electronics shortages, you may find them hard to obtain in the near future. Everyone needs to carry a spare WH igniter board with them anyway... lol (I don't, but I would if I had a spare one laying around) ~CA

[craigav]

Originally Posted by TWP723

Sounds like a regulator. It'll shut the gas off if it detects a leak. Does everything else work ok?

Just thoughts, I certainly agree that the regulator or gas supply or any number of similar things could cause an issue with the WH not lighting. Even simply being out of LPG when the RV'r didn't realize it.

I didn't mention these and items to check in my above comment in particular due to the OP stating "electronic igniter does not spark". That observation certainly needs to be double checked as when there is no spark then the WH is a "no" light for sure. ~CA

[Johnynorthland]

Originally Posted by craigav

Check to verify any parts I share here to make sure they apply to yours.

Generally speaking, I like to know what is broken prior to purchasing new parts, however sometimes I go a different route.

I would replace the electrode that you asked about because on the Atwood and likely other models the sparker electrode is also the flame sensor. If it failed completely then there would be no spark or flame sensor so the unit will try 3 times then quit trying until you do a reset, that is for safety reasons. With my comment here, I would certainly check all of the WH connections and in particular to the igniter\sensor first to it to make sure it is a completely dry connection and connected well prior to replacement.
https://www.amazon.com/dp/B07CNHLH6N...osi&th=1&psc=1

Second, while I would do what I mentioned first, the next likely issue would be with the igniter circuit board itself. Especially if it looks burned, or doesn't click when trying to turn the heater on with lpg (maybe they are solid state and don't click anymore though). Again as above, be sure to check all the wires coming into and out of the board and elsewhere to make sure that you are not dealing with a poor connection.
https://www.amazon.com/Atwood-91365-.../dp/B019COT1HC

This link is for a supplier of the boards that many people state are the most reliable replacement boards. https://www.dinosaurelectronics.com/Ignitor_boards.htm

An additional thought, while I would simply replace the igniter/sensor first if no other visible symptoms are seen, I would consider getting a board now as with the chip and electronics shortages, you may find them hard to obtain in the near future. Everyone needs to carry a spare WH igniter board with them anyway... lol (I don't, but I would if I had a spare one laying around) ~CA

Thanks, as always Craig, for your advice. I’ve checked all the connections, the spade on the thermo water heater cut off was a bit black so I sanded it to a bright copper. Everything else looks dry and clean. And Yes, board is still clicking but Still not lighting.


I’m ordering the igniter and and extra board like you said, if anything else just have for a spare.


I’m still open to more input on this topic from anyone else who’s had similar experience or advice.


Thanks again.

[Johnynorthland]

Originally Posted by TWP723

Sounds like a regulator. It'll shut the gas off if it detects a leak. Does everything else work ok?

Everything else works ok, except the igniter doesn’t fire. If the igniter has a probe on it to sense flame/heat, I’m thinking it may have failed. For $10 it’s worth a shot and if nothing else having a spare.


The thermal cutoff is also $10 for a pair so I’m ordering an extra also. A camper next to me a few weeks ago had his go bad after 2years of weekend usage.


Keep’em coming

[TWP723]

Originally Posted by Johnynorthland

Everything else works ok, except the igniter doesn’t fire. If the igniter has a probe on it to sense flame/heat, I’m thinking it may have failed. For $10 it’s worth a shot and if nothing else having a spare.


The thermal cutoff is also $10 for a pair so I’m ordering an extra also. A camper next to me a few weeks ago had his go bad after 2years of weekend usage.


Keep’em coming

Ok, then it's not the regulator. Now it's localized to the HWH. I agree, probably the igniter.

[JimD]

Since the gas valve is opening, the board is indeed trying to start in propane mode. At the same time the valve opens the spark should initiate. If there is no spark and no flame detected, the unit will shut down.

I would first verify the spark gap isn't excessive. The spark can only jump so far. Also, if there is water on the spark electrode area it could be shorting (not a term I like to use) the electrode gap. It wouldn't take much moisture to prevent the high voltage arc. Maybe try blowing out the area.

If the area is dry and the gap is good, the problem most likely would be the actual spark electrode or board, in that order.

I have attached some troubleshooting info. Since you mentioned using an ohm meter I did not attach my usual document on how to use a test meter.

[Johnynorthland]

Originally Posted by JimD

Since the gas valve is opening, the board is indeed trying to start in propane mode. At the same time the valve opens the spark should initiate. If there is no spark and no flame detected, the unit will shut down.

I would first verify the spark gap isn't excessive. The spark can only jump so far. Also, if there is water on the spark electrode area it could be shorting (not a term I like to use) the electrode gap. It wouldn't take much moisture to prevent the high voltage arc. Maybe try blowing out the area.

If the area is dry and the gap is good, the problem most likely would be the actual spark electrode or board, in that order.

I have attached some troubleshooting info. Since you mentioned using an ohm meter I did not attach my usual document on how to use a test meter.

Thanks Jim,


I got the flame to light with a grill lighter about 5 times, so even if the igniter was wet it’s certainly dry now after the flame burning 5 times for a brief period each time.


How would the gap change on its own?, plus there no “zap zap” coming from the electrode at all. I’ll look over your trouble shooting that you’ve attached.


I appreciate this very much!


Thanks

[TCNashville]

As stated above, the igniter has a dual purpose. One is to light the propane and the second is to sense flame telling the board to keep it going. Sounds like the board is doing it's job telling the igniter to light and hopefully a replacement igniter will do the trick. I've replaced one on both my water heater and fridge. Good luck!

[Johnynorthland]

Originally Posted by TCNashville

As stated above, the igniter has a dual purpose. One is to light the propane and the second is to sense flame telling the board to keep it going. Sounds like the board is doing it's job telling the igniter to light and hopefully a replacement igniter will do the trick. I've replaced one on both my water heater and fridge. Good luck!

Thanks TC

[Rock]

I had the same issue and a new board fixed that. Pull the two connectors on the board and spark wire and spray with contact cleaner. If still nothing take the two wires off eco t stat and jumper them.

[Johnynorthland]

Originally Posted by Rock

I had the same issue and a new board fixed that. Pull the two connectors on the board and spark wire and spray with contact cleaner. If still nothing take the two wires off eco t stat and jumper them.

Wow!, perfect timing Rock. I just received the thermal fuse and the new igniter I ordered from Amazon, installed them, and got the same results. So a new board it is!


Did you order it off Amazon or did you go for the better built one off that dinosaur website?

[Johnynorthland]

Originally Posted by Rock

I had the same issue and a new board fixed that. Pull the two connectors on the board and spark wire and spray with contact cleaner. If still nothing take the two wires off eco t stat and jumper them.

I took off all the spade constructions and sanded them with same results.


If I jump eco t stat and jump them and it lights then that’s the indicator the boards bad?

[Rock]

Dino board. Did u jumper the eco stat wires? Keep ur old board as a back at least it works on electric. Ur WH does work on electric! I have replaced Tstats three times for failure. The eco stat will not let either gas or electric light. Not sure about the other. Just pull the leads and jumper both. If still no gas it is the board.

[Johnynorthland]

Originally Posted by Rock

Dino board. Did u jumper the eco stat wires? Keep ur old board as a back at least it works on electric. Ur WH does work on electric! I have replaced Tstats three times for failure. The eco stat will not let either gas or electric light. Not sure about the other. Just pull the leads and jumper both. If still no gas it is the board.

Yes it works on 120 V as well as 12V when we travel.


I will try jumping, but of course it just started to rain here!


So if I jump out those wires and it works, does that mean board is bad?

[Rock]

No that means one of the tstats is bad. They r junk just like the board. The eco stat on the right has smaller wire connectors so u cannot connect to the wrong t stat.
Had to laugh one of the local dealers ( after our cat5 Hurricane Michael) was removing all the water heater boards from the trashed RVs. I bought one for $40 as a back up since I was living fulltime in mine again after the storm. I went thru that one also and now have Dino board.

[Rock]

I just reread where u said it works on 120 and 12 v. I never seen a 12volt WH, did u mean fridge or heater?

[Johnynorthland]

Originally Posted by Rock

I just reread where u said it works on 120 and 12 v. I never seen a 12volt WH, did u mean fridge or heater?

When we are traveling, I have the HWH on electric, however, I’m not running my generator, so I’m assuming it also works off 12V because there is hot water.


Maybe someone here can confirm or tell me it’s not running off DC?

[JimD]

Originally Posted by Johnynorthland

When we are traveling, I have the HWH on electric, however, I’m not running my generator, so I’m assuming it also works off 12V because there is hot water.


Maybe someone here can confirm or tell me it’s not running off DC?

Water heaters will run off electric (120 volts) if equipped or off propane which is 12 volts. Many water heaters don't include the 120 volt option but they all do propane/12 volts. The 12 volts is also typically used for control when operating in the 120 volt mode.