Atwood water heater problem

[hintro]

My Atwood hot water heater only works on propane. The electric element is OK, fuse is OK. The yellow wire to the relay doesn't have power to it even though there is power from the switch to the white wire on the module. When the galley switch is on I have 12V on the white wire on the module but no power on the yellow wire going to the relay. The red wire going to the ECO switch doesn't seem to have any voltage that my meter has been able to detect. Does that mean I need to replace the module or just a component in the module, or is the problem elsewhere? Works on gas but not on electric. Thanks for your help

[Old-Biscuit]

Do you have 12VDC on BROWN wires...from circuit board to/thru thermal fuse-T-stat and back to circuit board?

When on electric a millivolt current is sent to/thru ECO to gas valve solenoids to ground
Enough DC Voltage to be used tp place ECO into the control loop should T-stat fail
No millivolt...no electric operation

Works OK on gas cause it has FULL DC Voltage
If ECO/Gas Valve connections are dirty/loose or RED wire connection at circuit board not making good contact..no millivolt current (doesn't take much resistance to stop it)

Voltmeter '10' scale will not register the millivolts

Check ECO terminal/spade connections
Check gas valve terminal connections and GROUNDs
*Circuit board, gas valve solenoids
Unplug the 2 red wires off ECO and 'jumper' them together to eliminate the ECO

[hintro]

Thanks Old-Bisquet for your reply. No, I get zero voltage on the brown wire. The mil volts on red wire is .2 when I bypass the eco the heater still doesn't come on. I went ahead and ordered the control board.

[Old-Biscuit]

Originally Posted by hintro

Thanks Old-Bisquet for your reply. No, I get zero voltage on the brown wire. The mil volts on red wire is .2 when I bypass the eco the heater still doesn't come on. I went ahead and ordered the control board.

After the DC goes to circuit board via White wire (electric) then DC Voltage must go to/thru the thermal fuse/t-stat and back to circuit board BEFORE anything else is going to happen

Works on GAS so DC Voltage circuit on Brown wire and red wire circuit is good
Doesn't work on electric...no DC Voltage on Brown wire ...electric circuit on board bad

[hintro]

New controller board came, I installed it and now all is well. Thanks to all.
Roman

[Old-Biscuit]

Originally Posted by hintro

New controller board came, I installed it and now all is well. Thanks to all.
Roman

Thanks for update and resolution

Hot water GOOD!

[HaloThere]

This summer I found my Atwood GCH10A4E hot water heater WOULD work normally on gas, but would NOT work on my 120Vac.

I was in Mexico and there was no way to replace the Ignition Board, so I talked to the RV parks AC and Hot Water Tech "Egar" and he validated how I could hot water my system to operate on AC so I would not have to use my propane.

=== STEPS ===

YOU CAN HOT WIRE THIS CIRCUIT if your control board fails. Just provide 12V to the heating element relay, and if the relay is good, and heating element is good, then you should get 120V to the heating element.

TEMPORARY FIX so you can use 120V (free) AC power in a campsite to heat your HW tank instead of gas by doing the following:

1) Disconnect both upper and lower connectors to the control module and leave them floating. Also, turn off your HWH inside panel gas and AC-on switches.

2) On the upper (small) connector to the Atwood ignition board… strip-off strip-off a 1/4" of the insulation to the 12V White Wire and do the same to the Brown Wire.

Then connect the two wires together by twisting them and use black tape to hold them together. Do not cut the wire(s).

3) On the lower (large) connector to the ignition board… do the same thing (connect together) the 12V Yellow wire to the lower Brown Wires with black tape.

This will pass 12V to the YELLOW WIRE and will allow the heating element relay to pass 120Vac to the heating element to heat the water in the tank.

* Be sure to disconnect both connections to the control board.

Now your gas will NOT work, but your electric heating element will work.

==> And when you hit the road again, just undo the taped-jumper connections; and return the upper and lower connectors to mate with the control board... to get your gas working again!

==> Then order and new Atwood circuit board. For my HWH I found this one on Amazon For $55. (The Stealer wants $200+).

Part# 91365 Primeco RV Water Heater Control Circuit Board with Fuse Compatible with Atwood Water Heater 91226, 93305, 93851, 90097, 91346, GCH6A-10E, GC6AA-10E, GC10A-4E, GCH10A-4E,Electric12 VDC Gas

==> https://www.amazon.com/dp/B0CBSPD2P5...roduct_details

[HaloThere]

SUMMARY: How does the Atwood Control Board (aka Ignition Module) work to turn on and off the gas, and provide 12V switched-relay control to the 120V HWH heating element?

This control board uses 2 Normally Closed (NC) thermostats mounted directly to the tank:

1) The ECO = Electrical Cut Off Switch …ECO Opens at 180*F/Closes at 150*F. (82C is printed on the switch.)

2) The water regulating thermostat called a T-STAT opens at 140*F/Closes at 110*F. (60C is printed on the switch.)

Note: You can’t check your gas system when the water temp is above 110F because the T-Stat will be an open circuit.
Troubleshooting:

Think of the control board as a dual monitoring device. I.e., if you electric side is not working, but your gas side is, then you should start by checking the electric side wires first.

1) With the cabin-switch turned “on” you should get 12V to ECO (double Red Wire connection) which goes from the ECO to Gas Valve, and allows the control board to pass 12V on the YELLOW wire to the heating element relay.

2) Verify you get +12VDC White wire (for electric) and +12V on Orange wire (for Gas) at the circuit board when On/Off switches are ON.

NOTES: Concerning the electric 120V heating element, on my HWH there is no “reset switch” as some Atwood circuit diagrams sometimes show. This is because the newer control modules check for millivolts (of load) on the ECO circuit, and this monitoring acts like an automatic safety switch.

Concerning the Gas Heating Element Function: The control board also monitors the gas T-Stat that opens at 140F. These are the 2 BROWN WIRES… and the brown wire located closest to the burn-tube is protected by a thermal switch (aka heat sensing diode) designed to blow (open the circuit) when too much heat from the burn-tube blasts out of the tube, during ignition, and threatens to melt the wires.

Disclaimer: I think the above is correct, but if Old Biscuit says otherwise, you can follow his advice over my own.

[Old-Biscuit]

Originally Posted by HaloThere

SUMMARY: How does the Atwood Control Board (aka Ignition Module) work to turn on and off the gas, and provide 12V switched-relay control to the 120V HWH heating element?

This control board uses 2 Normally Closed (NC) thermostats mounted directly to the tank:

1) The ECO = Electrical Cut Off Switch …ECO Opens at 180*F/Closes at 150*F. (82C is printed on the switch.)
IF ECO Opens it will trigger FAULT LIGht and Lockout ----auto resets when temp drops below 150*F, water heater controls then can be reset by turning switches OFF/Back ON

2) The water regulating thermostat called a T-STAT opens at 140*F/Closes at 110*F. (60C is printed on the switch.)

Note: You can’t check your gas (or electric) system when the water temp is above 110F because the T-Stat will be an open circuit.
Troubleshooting:

Think of the control board as a dual monitoring device. I.e., if you electric side is not working, but your gas side is, then you should start by checking the electric side wires first.

1) With the cabin-switch turned “on” you should get 12V have a few Millivolts to ECO (double Red Wire connection) which goes from the ECO to Gas Valve, and allows the control board to pass 12V on the YELLOW wire to the heating element relay.

2) Verify you get +12VDC White wire (for electric) and +12V on Orange wire (for Gas) at the circuit board when On/Off switches are ON.

NOTES: Concerning the electric 120V heating element, on my HWH there is no “reset switch” as some Atwood circuit diagrams sometimes show. This is because the newer control modules check for millivolts (of load) on the ECO circuit, and this monitoring acts like an automatic safety switch.
Millivolt current from circuit board to ECO allows ECO to be part of Temperature Safety Loop. Otherwise water could continue heating if T-stat Failed to open. That would only leave T&P Relief Valve to vent off excess pressure. It pops open at 210*F/150 psi BUT heat source could still be active

Concerning the Gas Heating Element Function: The control board also monitors the gas T-Stat that opens at 140F. These are the 2 BROWN WIRES… and the brown wire located closest to the burn-tube is protected by a thermal switch (aka heat sensing diode) designed to blow (open the circuit) when too much heat from the burn-tube blasts out of the tube, during ignition, and threatens to melt the wires.
Thermal Fuse, T-stat, ECO & circuit board are all used by Gas & Electric.
Thermal fuse Blows when exposed to 190*F from Flame Blowback (obstructed burner/combustion chamber).

Disclaimer: I think the above is correct, but if Old Biscuit says otherwise, you can follow his advice over my own.

Minor corrections with some added information

[HaloThere]

Gracias Old-Biscuit!

Do you know how to hot-wire the Atwood in the event the electric side works, but the gas side does not? ...Or is that dangerous?

I'm also reposting a larger version of my Atwood 10A-4E wire diagram for easier viewing:

[Old-Biscuit]

Hotwiring so Electric will work......Not good topic unless one fully understands the T-stat & ECO must be in the temp control loop
W/O that water heater can become overheated/over pressurized and relying strictly on T&P Relief Valve to prevent an explosion

Typically when Electric is not working it is the circuit board, the DC Relay or the element
*Bad circuit board........then T-stat and/or ECO not functioning
(12VDC can be jumpered on Brown wires to/from T-stat but still need DC to/thru ECO w/o opening gas valve)
*DC Relay....contact burnt closed/can't shut off AC to element unless 15A CB is tripped

Instead of 'jury rigging' circuits....best to bite the bullet/run on propane and FIX Electric Issue ASAP

[HaloThere]

Agreed:

* Don't hot wire the circuit just to get the gas side working! I considered that too dangerous myself, but I thought I would ask.

Instead, do these few diagnostic checks when your gas side fails lite or to stay lit and 95% of the time one of these tips will put you back in business:

1) Wire brush the outside of you gas burner tube slots so that air will pass thru more freely. ...And chances are, maybe, that bellowing-sound will diminish when the gas burner ignites (TBD); and maybe the start-up "blow back" will be less too?

2) Remove the heat sensing diode and by-pass it. If you gas burner fires up you just found the problem.

3) The T-STAT (140F) thermal switch is a Normally Closed (NC) device designed to "open the circuit" when the water temperature reaches 140F.

To determine if this part failed, just disconnect the wire and use any automotive fuse to join the 2 wires together (aka you just made a jumper). And if you gas fires up you just found the problem.

IMPORTANT NOTE: These tips may help you fire-up when boondocking so you can have hot water, but you should never leave the gas or electric circuit "on" when you have by-passed either or both thermostats that touch the aluminum tank.

Likewise, if you ever find your hot water is getting TOO HOT then you may find you just need to remove the thermostats and wire brush the oxide build up that lies between the aluminum tank and the thermostat. And if that does not work you need to replace the thermostat switches which can be purchased for $15 on Amazon.

I also recommend you carry a back set of thermostats so you can change them when they go bad boondocking. It's just a 15-30 minute job once you have done it once or twice before.

=== ELECTRIC ELEMENT HOT WIRE NOTES ===

* I consider hot wiring the electric element element by joining a few 12V wires together safe enough, and worth while if you have shore power to heat your HW tank vs. gas, but I also think it is a good idea, for safety reasons, to turn "off" the electric switch inside the RV after you heat up the tank.