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mmcbride's avatar
mmcbride
Explorer
Aug 02, 2017

Hot Water Heater Just stopped working

Ok, so I am not what you would consider a newbie as I have been RVing in one form or another for about 40 years. I often do my own troubleshooting and repair for all things mechanical. I have even changed out a bad hot water heater element and thermostats.

The thing is, I am not 100% positive I have a thermostat issue but I am thinking that is the only thing left to try. I hate to have to remove the existing one as there is this form pad "glued" over the access to it.

For some background:

The MH is a 2017 Sportscoach 407FW.
The Hot Water Heater is a ATWOOD GC10A-4E 94018 10 GALLON HOT WATER HEATER GAS/ELECTRIC
The heater has been working fine ever since we have been on the road beginning June 9th.
Suddenly, no hot water starting yesterday.
The unit does not work on either electricity or gas.
We are on perfectly clean shore power in RV Park, no low voltage (I have a Hughes Autoformer) .
Everything else in the coach seems to be working just fine.
I have cycled the 110 Circuit Breaker.
I have checked the 2-amp fuse on the control board for the heater unit and it is not burned out/shorted.
I cannot locate any other "labeled" 12-volt fuse.
I have checked the propane and the tank is full, valve is open (wouldn't explain why not working on electricity anyway)
So, how does one actually check/confirm a thermostat issue, I mean to absolutely confirm it besides just replacing it to see of it suddenly starts working again?

Regards,
One stumped RV'er
  • mmcbride's avatar
    mmcbride
    Explorer
    Aug 03, 2017
    Old-Biscuit wrote:
    thermal fuse blow when exposed to 190*F.....flame/excessive heat blow back from combustion chamber

    T-stat has NOTHING to do with this.


    Flame sputtering......
    gas flow/air mixing is not in balance
    Remove burner tube.......clean with bottle brush
    Remove orifice....soak in alcohol and then blow dry.....very low pressure (just pucker up and blow on it) NO poking things thru it!!
    Run a wire thru combustion chamber and out exhaust... tie a rag to wire and pull back thru 'U' tube\

    Reassemble.
    Install new thermal fuse
    Fire it up...adjust air shutter so flame is Strong, BLUE and slight roar

    DONE..hot water (t-stat will shut down when temp reaches 140*F)


    Yep, did most all of that. Turns out that the gas nozzle and orifice had some calcium deposit that was retarding the gas flow. I suspect that some water that came out of the Pressure relieve value while with the dealer may have been the source of the calcium. In any case, I removed and cleand the orifice and adjusted the air shutter to the recommended 1/4 inch open, and viola, a perfect flame.

    I only hope this resolves why my TC blew and I have spares now.

    Thanks!
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Aug 03, 2017
    thermal fuse blow when exposed to 190*F.....flame/excessive heat blow back from combustion chamber

    T-stat has NOTHING to do with this.


    Flame sputtering......
    gas flow/air mixing is not in balance
    Remove burner tube.......clean with bottle brush
    Remove orifice....soak in alcohol and then blow dry.....very low pressure (just pucker up and blow on it) NO poking things thru it!!
    Run a wire thru combustion chamber and out exhaust... tie a rag to wire and pull back thru 'U' tube\

    Reassemble.
    Install new thermal fuse
    Fire it up...adjust air shutter so flame is Strong, BLUE and slight roar

    DONE..hot water (t-stat will shut down when temp reaches 140*F)
  • rk911's avatar
    rk911
    Explorer
    Aug 03, 2017
    mmcbride wrote:
    ...The thing that has me worried is that the gas flame sputters quite a bit, almost like maybe getting too much air. I will try adjusted the sleeve that controls air flow.
    Now, back to that bad/blown Therm-custoff fuse, I do not see a reason for it just blowing unless it is getting too much heat back-blow from the burner. Is it possible that the flame being out of adjustment could have caused the issue? Or might the t-stat also be bad and have something to do with it?


    that's exactly what happened with our WH (same model as yours). the thermal cutoff (TC) had blown and once I bypassed it the WH worked again. I picked up a couple of new TC units, used one to replace the bad one and kept the other as a spare. they are very inexpensive and EZ to replace. beyond that I would adjust the flame as needed. and you don't need a by-pass wire...just connect the brown wire from the control board to the TSTAT terminal.

    mmcbride wrote:
    Would it be wise to replace the t-stat and the thermal cutoff fuse at the same time, or is that overkill?

    overkill in my estimation. the gas flame can be adjusted so replace the TC, adjust the flame and go from there.
  • drsteve's avatar
    drsteve
    Explorer
    Aug 02, 2017
    The sputtering flame may have caused the thermal fuse to blow. It also leads me to believe you may have a bug nest in the tube. Spiders in particular seem to love propane. Pull the tube, clean it out, but do NOT shove a wire or anything else into the orifice itself. It is easy to damage that tiny hole.
  • mmcbride's avatar
    mmcbride
    Explorer
    Aug 02, 2017
    So, after making a by-pass wire, I was able to test both the t-stat with the thermal cutoff and w/o the thermal cutoff fuse. The water heater did not fire up with the thermal fuse in the circuit, but did work when removed. The thing that has me worried is that the gas flame sputters quite a bit, almost like maybe getting too much air. I will try adjusted the sleeve that controls air flow.
    Now, back to that bad/blown Therm-custoff fuse, I do not see a reason for it just blowing unless it is getting too much heat back-blow from the burner. Is it possible that the flame being out of adjustment could have caused the issue? Or might the t-stat also be bad and have something to do with it?

    Would it be wise to replace the t-stat and the thermal cutoff fuse at the same time, or is that overkill?

    I could just call coachnet and have them send someone out to trouble-shoot the whole thing, but then I would have to pay them and try to get reimbursed from the manufacturer since is under warranty. Or, I could try to get a Dometic/Atwood service center to come out under the Atwood warranty. Such a hassle though, almost easier to fix it myself if I can.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Aug 02, 2017
    Got to have 12V DC going to the ON/OFF switches (electric & propane)
    Then that 12V DC goes to the circuit board....White wire/electric and Orange wire/propane

    Then 12V DC comes out of circuit board (Brown wire) ...goes thru a thermal Fuse then to t-stat
    From t-stat back to circuit board (Brown wire) then out of circuit board to ECO and gas valve (RED wire)........ECO circuit has voltage on electric or propane.
    Electric is just milivolt and propane is full 12V


    BUT that 'thermal fuse' (inside the clear tubing...connected between circuit board and t-stat) is a ONE time fuse..it blows and shuts off ALL DC to rest of circuit so NO electric or propane function
    Thermal fuse blows at 190*F ....due to blow back of propane flame out of combustion chamber

    I doubt your issue is the t-stat........bet it is a blown thermal fuse
    Just unplug it and plug brown wire into t-stat and try water heater.
    Could be obstructed combustion chamber....spider webs, nesting OR thermal fuse just too close to flame.

    If WH runs W/O thermal fuse.......you can operate it that way until you get a new thermal fuse.


    If not thermal fuse..bypass the t-stat and check operation..then replace t-stat (t-stat/eco come as a set with a new insulating pad)

    But I will be surprised if its the t-stat :B



    On Edit:
    Here is a colored version of the wiring diagram for your Atwood

  • darsben1's avatar
    darsben1
    Explorer
    Aug 02, 2017
    If it is under warranty call the manufacturer and see if they will pay a mobile repair person to come fix the problem. Watch him and learn
  • wrgrs50s's avatar
    wrgrs50s
    Explorer
    Aug 02, 2017
    If I am recalling correctly you can make a jumper wire and unplug the terminals on the thermostat, then place your jumper wire between the two female ends.

    This should bypass the thermostat. Turn the switch on for propane and if it fires up you have a bad thermostat. If that don't work, jumper all the way across to the opposite side of the eco, bypassing both.

    If neither does the trick, take off the circuit board and take to an RV repair shop and have it tested. Most shops have a circuit board tester.

    Also, before doing anything, plug and unplug, and wiggle all the wires on the eco and thermostat terminals to be sure they are making good contact and see if that does anything. Sometime they just corrode just enough to cause an issue.

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