Atwood Water heater wiring Question

[Wbago]

Hi guys, me again lol

Due to the hopelessness of the so-called heater engineer who was scared to even try to look at my issue, i find im trying to fathom it all myself, again ... he had the cheek to ask for a call out charge too

Problem is as follows:-
Atwood water heater, switches on fine, ignites and fires fine, cuts out a few minutes later, anything from 1 minute to 20 minutes ... turn it off and back on, fires right back up, does the same cutout a few mins later ....
after reading all i have found, im now at a point where ive got a question and no answer, so before i buy thermostats and tinker with it, i figured id ask here . .. .

Question is:- .... when i turn heater on, there is 12+ volts at both sides of the thermostat ... this is as it should be .. . after it shuts itself off, theres NO voltage at EITHER side of the thermostat .... the power into the heater is supposed to be straight from the on/off switch, and according to the wiring diagram, there is no break or fuse between the switch and the thermostat .... so what is killing that power?? .... shouldnt that have power even though its turned off??

awkward bugger, aint i ??

[Stripe]

Here's a question, does it turn back on by itself after a while?  Mine will fire initially then shut off when the temp is reached. If I use enough hot water it kicks back on again to reheat the tank. Not sure if there is supposed to be power while off, but I would say if you have the time, see what happens.
If it dun go boom, you're good..

[DaveVA78Chieftain]

You did not indicate which model heater you have however due you have a Thermal Cutoff on yours?





It is used to detect excessive heat for situations like the exhaust port being plugged (heat is pushed out the intake port).  If so, it may have an intermittant problem.

The fuse in the power center or a 12VDC power wiring connection may be weak and opening up from heat when current is pushed through it.  Check power at switch when the problem occurs.

Dave

[Wbago]

Stripe - no, it doesnt kick back in .. when it dies, the red non-ignition light comes on, and it stays off ... i doesnt even try to re-light. ...
. it SHOULD heat the water to 60 degrees, then the thermostat should open, cutting the power, stopping the burner ... when it cools, the thermostat closes again, burner relights, reheats, trips out again ... sounds like yours works fine ... question for ya . .when yours cuts off, does the water heater light come on inside the coach? cos yours shouldnt, mine does

dave - yes, theres a thermal fuse, yes, its fine, same happens with or without it. not sure of the model cos i see no model numbers. its a 6 gallon heater, no electric option, just LPG, thermostat and eco is outside, just like your picture ...

ive looked at the wiring diagrams, and there is NO FUSE between the thermostat and the on/off switch (not counting the thermal one) ... there is power at the switch all the time, no issues there, but when it dies there is NO POWER to EITHER side of the thermostat.

so the question is: .... if theres power at the switch, why no power at the thermostat? ... according to the diagrams, the power should go to thermostat FIRST, then into control circuit ... if theres a problem, the control circuit turns it off, BUT it turns it off by cutting power to the gas valve, not to the thermostat, so there would STILL be power at the thermostat if the circuit board turns the heater off ... i think.

really i need someone to check on their heater, so i know if thats normal or not lol

[Wbago]

found the model number, its GH6-4E .... PO had removed the sticker and put it in the documents, for some odd reason ....
just ordered new thermal fuse, and new ECO and stat .... will swap out and see if that sorts it  Hm?

[DaveVA78Chieftain]

My questions are based on your symptoms so, if:

but when it dies there is NO POWER to EITHER side of the thermostat.

Then:
1) The switch is bad (bad contacts such that it heats up then opens up when current flows through it)
2) The unit is wired incorrectly.

I am assuming you are measuring voltage at the thermostat from each side to ground; not across each terminal of the switch (across it would read most likely read 0VDC with or without voltage applied).

Also, wiring drawings indicate the GH6-4E did not have the Thermal Cutoff.  Could have been added but was not original so someone may have miswired something.  Thermal cutoff started at revision GH6-7E.

Dave

[tomlee47]

I have the same problem plus have noticed by direct observation that the igniter keeps sparking the entire time the flame is lit regardless of run time whether one minute or fifteen.

[Wbago]

Dave - no, theres no thermal fuse in the wiring diagram, but its listed in the parts list for that model, so ive ordered one on the offchance, as it cant hurt lol
the wiring diagram for this model also shows 2 switches, lower one is the power, upper one is connected to circuit board, any idea what it is, cos i dont seem to have it anywhere ?? ... unless its the light on the panel ?
yes, measuring from each to the ground wire, i get 12+ when its burning.

also, apparently the sensors might be the wrong way round, so the eco cuts off way early, and the circuit sees it as a high temp fault and goes to lockout ... im not gonna swap em, ill wait till i got the new ones now. . .

[Stripe]

No light after initial switching on.  I do remember it staying on one and it trying to ignite the burner and couldn't understand why until I tried to heat up water on the stove, only to notice that (like a spastic) I neglected to turn on my gas after pulling into our campsite..

[Wbago]

yours is working right then, stripe ...
apparently the light should just flicker at switch on, then stay off unless theres a problem (like no gas lol) ...

[Stripe]

Right, and believe me, the gf dun let me forget about that even today..

[M & J]

I like K's style.

[Wbago]

new ECO and stat resulted in . . . .. . .. . NO CHANGE !!

now looking at a new circuit board i think, unless you guys know or anywhere i might get a pre-owned one mebee  ?
or another alternative/solution?
can it be bypassed at all 

part is Atwood 91504, replacing mine, which is a 91420, according to parts list .. . 125 of your bucks new

[Stripe]

Wbago have you tried removing the spark igniter and clean the contact points with a contact cleaner?  Also try doing this as well;  remove the screw holding it to the tank and clean both surfaces too. When done put it back together and be sure the igniter will be in the flame. It should turn red hot, this tells the circuit board there is flame.  If this doesn't help consider replacing it...

[Wbago]

yup, sanded and re-crimper all connectors and spades, removed circuit board, cleaned all those contacts, and the earth wire, swabbed the vent tube, still no joy

burner seems fine, sparks, lights, nice strong blue flame, red hot thing is the sense circuit, thats fine too .. .
solenoids seem ok, look nearly new, only thing i havnt done is rip it out and shake it ...

and nowhere i can find to test my board to be sure before i buy one, either

[DaveVA78Chieftain]

If the unit is wired correctly, then all I can say is if the voltage disappears at both TSTAT terminals (when measured to ground) then it has to be the ON/OFF switch (opening up due to heat build up when current flows through it).  Even a fuse at the DC distribution panel could do that.  Try a jumper at the ON/OFF switch from 12VDC to the brown wire first.   The brown wire is power to the unit that first goes to the TSTAT.

Dave

[Wbago]

havnt rechecked that, actually, think i might have had an iffy earth connection on my tester  W%

ill pop out now and retest it, but .....
IF its the switch or the live into the unit that fails .. .how does the board still have power to light the error light on the panel ? ... .if the switch fails, surely theres no power to the board, and the whole thing just dies till the switch has cooled down? .. .

[Wbago]

Defo a live at the stat both sides, after the failure ... this time lasted about 12 minutes before it locked out ...

ordering part now, from Dayton Ohio, crossed fingers and toes

[Wbago]

$178 with shipping and customs ...... 

[Stripe]

Post the price in £ it'll look cheaper to us..

But seriously, Wow, that sucks.. So it's the switch then?

[Wbago]

nope, at lockout the switch is still good ...

[DaveVA78Chieftain]

how does the board still have power to light the error light on the panel

Either I missed you saying that or you didn't say that before.  If the light is coming on when it fails, then yes the board is getting power.  So, sorry, but yes you appear to be down to just the board as the problem.

Dave

[Wbago]

New board installed, partial test today resulted in nice hot water, but no water in the holding tank meant i couldnt run it for long to test that it turns back on when cooled down, but when it turned itself off, there was no red error light, so i think im good
photos tomorrow, ill also scan in the instruction paper, for future reference ...

fitting was cake, took around 20 mins

[moonlitcoyote]

The light on my water heater (inside) stays on when the water heater shuts off due to the water being hot. At that point I just shut the switch off unless I run out of hot water and need to start it back up.

[Stripe]

Cool..