Atwood GCH10A-4E Water Heater Not Lighting On Propane Alone

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satouch

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Feb 28, 2018
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Hello, I have an Atwood Water Heater (GCH10A-4E), it will heat water on electric alone, but the LP will not light if it's on LP alone.  There is spark, ECO and Thermostat and fuse have been checked and are fine.  Here's what I don't understand, when I flip on the electric AND the LP at the same time the LP will light and stay lit just fine, turn off the electric switch and the LP immediately turns off.

I am leaning towards a problem with the circuit board but want to be sure before ordering the part, I also think it could be the gas valve (however, it is working fine when the electric element is turned on).  Has someone else had this problem?  Is there an easy way to confirm whether it is circuit board or valve?  Or could it be something else?

Thanks
 
Odd that electric on makes the gas work, and that does indeed suggest a faulty circuit board. It seems obvious that the gas valve itself is working or the burner could never light, but its possible the circuit board is not sending 12v power to open it when in LP mode only. You should be able to verify +12v to the valve during the gas ignition sequence (while the sparker is working).

Are you sure it is the electric mode that gets the gas burner working? Could it be better 12v power, that happens to be present whenever shore power is available? The RV converter/charger provides higher voltage than battery alone, so maybe enough t make a difference.  If you try gas mode alone while the rv is on shore power, does it work?
 
Hi Gary, Thanks so much for your interest.  This is indeed odd.  All of my attempts have been while connected to shore power (although the same thing happens when not connected), as well, I have a battery maintainer connected to my engine battery, so all the batteries should be providing full 12v  at all times.  I did have the idea overnight to check the voltage to the valve in both Gas alone, as well as, gas and electric mode...  If there is a difference, then that should verify the the valve is not the problem... 

Thanks again...
 
Okay, so I called Atwood and explained the situation to them and their response was "no, that can't be happening"  LOL 

However, they did tell me to do more testing on the wires.

Here's what I have found.

12 volts is coming from the switch to the circuit board.

When I disconnect the brown wire coming from the circuit board to the thermostat sensor I have 12 volts coming out of the circuit board to the Thermostat.

When I disconnect the brown wire that goes back to the circuit board I have 12 volts coming out of the thermostat sensor and through the thermal cut off.

However, when it's all connected and making the full circuit from the circuit board and back to the circuit board, the voltage drops to 3.9 to 4 volts.

I'm gonna check a few more connections, but at this point it seems as though something in the circuit board is shorting the the 12 volts and dropping it to 4 volts, however, when I turn the electric part of the heater back on, it goes back up to 12???.

 
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