Atwood GC10A-4E HWH fires on LPG, but takes several tries to keep burning ... and then it quits some minutes later :(

[ak2handr]

'06 Monaco Neptune 36PDQ, 49k miles, water & LPG tanks full, all new batteries

"Bertha" named by Teri, my smarter half, after "Bertha Butt, of the Butt Sisters" song, has sat since DMV inspection in 2020.  I've spent the past week un-mothballing her, and hacked my way through spiderwebs with a torch and machete, to the rear bedroom & Dometic/Atwood HWH at the rear. I drove her to inspection at local CW store. She now runs great, but the fridge (different thread) and HWH are not working. HWH shows no signs of life.

   After I cleaned & treated the electrical connections to the two T-stats, the card edge connectors, 2A fuse, and HV igniter on the control board, I *finally* remembered the 12 vdc switch inside has to be on in order to run on LPG.  Flicking that on rewarded me with the 3 prescribed sessions of the igniter clicking and concomitant roar of gas.  I scurried outside and waddled to the rear to catch the third (of 3) lighting attempts.  Happily, I could see the arc at the igniter's contacts and a long, blue flame blowing down the combustion chamber. 

Unhappily, as soon as the igniter stopped, so did the satisfying flame.  As soon as I realized I could reset the igniter's attempt counter by just pulling & reinstalling the 2A fuse, I proceeded to perform that action 10 or 12 times.  Finally, the flame kept going, as if a thermocouple had finally been satisfied by heating up to some activation point.

I waddled back inside to await a flow of mercifully hot water at the kitchen.  That never occurred. Another excursion to the outside right rear of Bertha showed the flame and LPG flow had both stopped.

   I have downloaded the service manual, but I am unable to discern how the burner knows that there is adequate flame to enable the gas valve to remain open.  The only component I can see that's in the flame that might serve as a thermocouple is the igniter assembly. Is it possible the igniter probe also serves to report some signal back to the control board? Like, when it's not actively sparking, that terminal on the control board switches to working as a sensor? The ground side of the spark gap was glowing red when the flame was on it, (and while working as an igniter.)  Interestingly, I noted the HV wire between the Control Board and the igniter does not make good contact. The black wire is not fastened to the igniter. There is a goober of silicone caulk around where the wire enters the porcelain electrode holder.  The HV easily bridges the teensy gap between the end of the wire and the electrode, but I suspect it's an open circuit to DC, in case that electrode does function as a sensor to show flame is present, but I dunno for sure.  I will have a new igniter assembly and two thermostats Sunday, via Amazon.  

Both the T-stat and ECO switches remain closed on during all of this cycling.  Do my symptoms indicate a bad igniter electrode. or maybe an intermittent sensor? I've ordered a kit with the two T-stats and new ignitor, they'll be here Sunday.  I don't want to keep throwing good money bad by "shot gunning a diagnosis" and replacing parts willy-nilly.

  So, any (printable) suggestions?  

Thanks,

Barney  KL7HNY

diddly dahdidah        dit dit

 

Edited August 30 by ak2handr
forgot to mention the broken connection inside the igniter; significant?

[RNMCBR]

Yes, that’s the way your refrigerator igniter works. You could try cleaning the igniter with a scotchbrite  pad. 

[ak2handr]

4 minutes ago, RNMCBR said:

Yes, that’s the way your refrigerator igniter works. You could try cleaning the igniter with a scotchbrite  pad. 

Great, thanks.  The igniter spark is plenty strong. When the loose black wire came out of the igniter base, it was sparking to any nearby ground, including my fingers <ouch!>  But as long as it's pushed down to the end of the porcelain, the igniter does great. I just edited the OP to show the bit about the loose HV lead.

   I'm also fretting over a dead fridge, so your answer will help me there, too.  I haven't yet figured out where the LP igniter for the fridge sits, but that isn't working on any of the three power sources.

[RNMCBR]

The Lp igniter for the fridge is located in the burner box. Follow the igniter wire from the control board. See attached picture. It’s held in by a single phillips screw. I use a long extension to get around the tubing. While in there, you should clean it and also remove and clean the burner tube. It may have rust inside it that has dropped down from the boiler stack, which could affect flame quality and cooling performance. 

[ak2handr]

Excellent! I'll scurry outside right away and see if I can get to it before I melt in the +105F heat index outdoors.   Thank you!   It'd be great to get it running on propane, even if the 12V and 120V modes don't work.  I'll letcha know.

--  Barney ==

[RNMCBR]

Yes, please let us know. Thanks

Oh, BTW, you will need to remove the sheetmetal box first. I also remove the drip pan. 
Also, removing the gas tube from the burner is easier if you use a bent 1/2” open end wrench like the attached picture shows. 

I bent this one after heating it with an acetylene torch. 

[cbr046]

5 hours ago, ak2handr said:

Unhappily, as soon as the igniter stopped, so did the satisfying flame.  As soon as I realized I could reset the igniter's attempt counter by just pulling & reinstalling the 2A fuse, I proceeded to perform that action 10 or 12 times.  Finally, the flame kept going, as if a thermocouple had finally been satisfied by heating up to some activation point.

I waddled back inside to await a flow of mercifully hot water at the kitchen.  That never occurred. Another excursion to the outside right rear of Bertha showed the flame and LPG flow had both stopped.

 

I had spider mites (or some really small critters) clog the orfice of a furnace once.  It would light on the little amount of gas coming through the orfice but not stay lit.  Once inside the burner chamber I discovered a muddobber nest inside the burner.  So I'd recommend complete disassembly of the HWH. 

As for the fridge . . . . You didn't say what kind (Norcold?).   If it doesn't work on 120V I doubt it will work on propane.  But the heater elements could be burned out so a quick test would be putting a DVM on the heater leads and see if you get voltage (in AC mode, of course).  If not working on AC the fridge may have been disabled by safety devices.  Are you familiar with the "magnet reset"?

- bob

[ak2handr]

7 minutes ago, cbr046 said:

f not working on AC the fridge may have been disabled by safety devices.  Are you familiar with the "magnet reset"?

- bob

I tried a magnet on the upper right corner of the overtemp board at the top of the compartment, with 12volts in & out, grounds, and a teensy 2-conductor plug. Either that wasn't the problem, or the cheesy Hazard Fraught store magnet isn't strong enough. Amazon is supposed to deliver a stack of neodymium coin magnets this evening or tomorrow.  The red LED remains illuminated as long at the 12VDC & ground on its left side are connected. No 12VDC appears at the appropriate terminal.  I bypassed the unit with my DC ammeter (in to out) without effect.

 

[ak2handr]

20 hours ago, cbr046 said:

I So I'd recommend complete disassembly of the HWH. 

As for the fridge . . . . You didn't say what kind (Norcold?).   If it doesn't work on 120V I doubt it will work on propane.  But the heater elements could be burned out so a quick test would be putting a DVM on the heater leads and see if you get voltage (in AC mode, of course).  If not working on AC the fridge may have been disabled by safety devices.  Are you familiar with the "magnet reset"?

- bob

Bob,

  I'll tear into the HWH as you suggest. It's kinda hard to get to the 120-volt element, buried as it is inside the  bedroom closet.

On the fridge, I realized I don't really have a good idea of where the electric heater is, so I can't really "ohm it out" to see if it's open. I like that possibility. I was just about to order a replacement "power board" for it until I pondered the folkowing:

   I realize that, in both appliances, I don't know where what I assume must be a thermocouple lives  that would enable the continuing flow of gas to the burner. Does the igniter do double duty as a flame sensor when the control board isn't supplying HV to the spark gap?

  I'm used to the thermocouple on natural gas home appliances failing after years (or sometimes months) of direct flame impingement by a pilot or main burner flame. When I went looking for them in the HWH & fridge manuals I came up empty. 

   Where is my reasoning faulty?

-- Barney --

[cbr046]

It's part of the burner assembly.  Google 'Atwood Thermocouple' on Amazon and you'll get plenty of examples.  BUT I DON'T THINK THAT'S YOUR PROBLEM.

On the fridge control board you'll have 2 (or 4) wires from the control board to the boiler stack covered in sheet metal.  2 wires go to the burner, 2 wires go to the snap-disc safety device . . . . but it could be 2 wires total with the snap-disc in series with the heater element.  You can pick up those wires on the control board, there may even be a hint label. 

Norcold control boards are horrendously expensive.  Look up Dinosaur Electronics and see if they have a control board for your model.  Same for the HWH if you go that direction.  The Dinosaur boards are better made than OEM.

If the control board isn't turning on the fridge heater I'd suspect the safety device - a separate board that tells the fridge control board it was once unsafe to run.  I don't know your fridge model so hard to say what's in there.  Norcold 1200?  Some can be reset with a strong magnet (Google / YouTube it).

- bob

[ak2handr]

Norcold 1200RLIM        I had been using a separate thread covering the fridge, concurrent with this one. 

Is the fridge safety device the separate board above the control board, with the red LED? 12vdc & GND in, on the left, a teensy 2-pin Molex connector with 2 teensy wires, and a 12vdc output (that is not outputting.)  Amazon's promise of my strong magnet order arrival was just so much vaporware, but they're going to try again tomorrow. 

I also tried the   "Pin 15 to ground for 15 seconds, wait for the click" main board reset, but it didn't click/reset. 

With your guidance (thank you *again*, BTW) I now see the "'AC heater wires" from the main board, which run up to the top of the ~12-inch-tall insulation blanket that wraps around the structure above the flame box. 

Each end of the metallic tubes that disappear downward from the top has one yellow and one black lead coming out of (or going into) it.  Once disconnected from the control board, each pair of those leads "ohms out" at 60 ohms +/- 1.5 ohms.  With the fridge and icemaker power plugs inserted into their respective receptacles, each of the "AC HTR HI" to "AC HTR LO" displays ~52 or 53 VAC.

Just now, on a whim (and throwing caution to the winds) I took the dependent/output 12VDC wire from the overtemp/safety/WTH-is-it? board at the top of the compartment, and plugged it onto the 12VDC terminal on the board -- the one from where another lead took that 12VDC to the ... I'll just guess and call it the "overtemp board."  

I waddled hopefully up into Bertha, went to the eyebrow board on the fridge, and pressed the Power button.  After I regained my composure and got myself up off the floor, where I'd fallen in surprise, I was rewarded with "Au".  Successive keypresses took me to "Ac" and "Lp."  A gusty roar from the flamebox area, and warmth at the top of the Fibreglas jacket, lead me to believe that, "Alive, alive -- Oh, it's alive!"  (with apologies to Gene Wilder as "Young Frankenstein."}

Now I'm concerned that the overtemp board has been doing its job, saving me from a nocturnal immolation.  That would be embarrassing, as a retired firefighter-paramedic from Alaska....then a police arson investigator......They'd take away my birthday.....

I suppose I may fairly surmise that, somewhere in all my disconnecting & reconnecting of connectors to the control board, I blindly removed enough corrosion (aided by liberal applications of Caig DeOxit D100L) and lucked into fixing it.  But now I'm worried that the overtemp board, which was preventing 12VDC from getting to the main board, was faithfully protecting me from myself and my admittedly amateurish troubleshooting. And, at this point, I've got no good idea of what might have caused it.  When Amazon next arrived with my stack of 110-lb pull neodymium magnets, I can try resetting said overtemp board. If it *does* reset, does that mean I may more-or-less safely carry on and call it fixed?

Y'all folks  (the locals here in NC speak like that) are wonderful, patient, and helpful beyond belief.

Speaking of which: do the voltage & resistance readings I reported a few paragraphs ago see like ballpark for what I should expect?  I'm guessing that the AC volts on the heater terminals are each just about half of typical line voltage, minus a bit for resistance in all the conductors & connections?

I remain, 

Hesitantly yours,

-- Barney  KL7HNY --

 

Edited August 31 by ak2handr

[cbr046]

1 hour ago, ak2handr said:

Now I'm concerned that the overtemp board has been doing its job, saving me from a nocturnal immolation. 

 

Maybe, probably, maybe.  What you need to do is get the overtemp board reset and monitor the fridge closely.  If it fails again in the next day or two IMO you're looking at replacing the fridge.  I wouldn't bypass the overtemp board other than testing.

I  did the "pin 15" reset on my daughter's fridge (after she attempted it) and it's still working, but the instructions had to be followed to a 'T'.  I'm just glad it worked.  On my Norcold 1200 I had to reset by magnet once and that lasted (a year?). 

Your heater elements should draw ~3A.  The half voltage doesn't sound right.  Does the VAC jump to 120 with the heater wires disconnected?

- bob

[ak2handr]

1 hour ago, cbr046 said:

Your heater elements should draw ~3A.  The half voltage doesn't sound right.  Does the VAC jump to 120 with the heater wires disconnected?

- bob

Sounds like good advice.  I have just now stepped out of the shower, so I shall test that VAC tomorrow. In the meantime, I'll scurry out and turn the fridge off.  I have a decent AC/DC clamp ammeter, but for such low current I'll just meter it with a regular series ammeter; I find that more accurate.

Edit: Update, 20 minutes later:  I restored the overtemp board so it's inline in its designed config.  I'll try resetting it when Amazon brings the fancy-schmancy magnets tomorrow. Also, interestingly (at least to me) when I checked inside the fridge just now, it was room temperature, and the interior light isn't on.  But both freezer compartmens are nice & chilly. 

   I remember seeing someone here had a similar problem. I'll look to see what fixed that. I've had that happen with my home fridge; I believe it was an open circuit in the fridge defrost heater wiring.

-- Barney --

 

-- Barney --

Edited September 1 by ak2handr

[cbr046]

1 hour ago, ak2handr said:

when I checked inside the fridge just now, it was room temperature, and the interior light isn't on.  But both freezer compartmens are nice & chilly. 

   I remember seeing someone here had a similar problem. I'll look to see what fixed that. I've had that happen with my home fridge; I believe it was an open circuit in the fridge defrost heater wiring.

 

1.)  Normal.  The freezer always cools first.  The light could be a burned out bulb or bad contacts.

2.)  I remember reading that too . . . . somewhere.

- b

[ak2handr]

So, back to my errant Atwood HWH:

(I've just now updated my Norcold fridge testing over on that thread)

Yesterday, just as dusk was falling, I installed the new thermostats, thermal fuse, and igniter/sense probe.  I enabled 12v/propane heating and was treated to a nice blue flame at the end of the flame spreader, after polishing 20 years' worth of rust & corrosion off of all the burner components.  I also removed the flue box (more on that later) and washed out the whole combustion chamber and up to the top end with a refrigerator coil brush and lots of running water. After making sure the 10-gallon vessel was full of water, I "fired the boiler" on just propane. I called it a day and periodically peered out in the gloom to see (and hear) a healthy propane fire.  This morning, the flame was gone, and all four running water appliances gave out great hot water (like, hot enough to scald.)   And yup, I got the 140 & 180 dF thermostats in the correct positions. 

  Now, however, I'm confused with the placement of the three flue box parts.  Before I took it out of the control cavity, I'd noticed there was a sort of baffle plate that was loosely placed *somewhere* within the folds and spaces of the larger, more elaborate box assembly. There was also a rather fragile, thin gasket that looks like the seal in a Ball Dome canning jar's lid. I'm assuming that the smaller piece of sheet metal, with the 90-degres bent ends, is for occluding part of the upper, "output" port in the upper left (or upper rear) position in the control cabinet.  And I don't know where the fragile gasket-thingie goes.  The circular hole in all 3 parts matches the diameter of the upper "stack".

    I was unable to find any photos or explanations in the Service Manual (thank you again, whatever nice person posted that link.)  Does anyone have either a fairly simple written description, or a photo, that shows how these things fit into place? If the smaller sheet metal device had been snugly in place as I disassembled it, I'd have been able to replicate it upon re-installation. Presumably it's meant to somewhat slow the exit of the products of combustion, thereby allowing more heat to transfer from the "chimney" to the hot water vessel...?  I can see where choking down the outflow a little would make for more efficient heating, but at some point there's likely to be a safety issue as those same products of combustion are retained so close to the interior of the coach (in our case, right outside the aft bedroom.)

Here is a pic of the three components I removed (and cleaned.):

 

Edited September 3 by ak2handr
adding pic of 3 flue box parts, and typos

[ak2handr]

Woohoo!

   I'm not sure why I didn't think of this answer earlier....sometimes I'm such a "maroon"....

  Teri, my wife (who is many times smarter than I am) queried, "Why not just run by the Camping World where we bought Bertha and ask to see an RV that has the same HWH?"    

Oh.  "Why, sure, Honey, sounds like a great idea!"

They know me pretty well there (Statesville, NC) ever since I took this white elephant off their hands in 2017.  We stopped in, and a local tech came scurrying out to drive me around their Used Inventory lot to a trailer that had the same GC10A-fE HWH as we have.  The tech went peering around, and sorta wedged the flue box away from the inside wall of the HWH.  "There it is," he pointed out.  I was able to see one end of the rectangular baffle, facing the "right" side of the flue box, or pointed towards the front of the coach, toward the ignition control board.  A fingertip pressed into the gap told me that the 90-degree flanges were pointed in, towards the wall of the heater, almost like legs to hold the whole assembly ~1/4-inch away from the wall.

   I was also able to see where the ring & gasket get positioned: around the combustion/bottom end of the chimney.  The gasket goes against the wall, and the ring goes around the "pipe" to hold the gasket tight against the wall.

   I'll post a couple of pics when the ring-and-gasket parts arrive from Amazon tomorrow.

   Thanks for everyone's patience on this topic.  I figure this is the kind of problem that no one else has ever had, but all my experience with gas-fired appliances and wood stove dampers is deep in my past, from my 30 years in Alaska.

   Pics to follow, tomorrow.

-- Barney -- KL7HNY