Atwood Water heater won't work on gas

bjarnold wrote:
It's a 2007 and the model is GC6AA-10E. I cleaned the terminals on the circuit board and I have 13 volts coming into the circuit board via the orange wire on the top plug

OK this helps greatly knowing you have the newer control system.

You said this"

bjarnold wrote:
Atwood gas/electric water heater with DSI and it works fine on electric but does not work on gas. The gas valve does not open, the ignitor does not fire, the red light on the switch panel does not light up. I bypassed the thermostat and still doesn't work.

On that newer unit, the control board runs both the gas and the electric relay to the electric element. The safeties are working for both. Meaning, if it works on electric, then the T stat and the Thermal fuse are or were working.

Your's does have the thermal fuse. Or at least the part number shows it does. This is a small resistor looking deceive that is normally plugged onto the terminals of the T stat with a clear tube cover and and then the brown wire on the end of it goes back to the control board. The thermal fuse is called "thermal cut off" in Old Biscuit's diagram.

Have you tried this back again on electric? OR do a voltage check on the control board pin that has the brown wire from the thermal cut off fuse that goes back to the control board. Do this at the board so you know the safety circuit is in tact. Point being, need to make sure you did not make the safety circuit not work by fiddling with the wires. Easy to do.

If it works on electric and it does not work on gas, and while on gas it does not start the ignition (click, click, click) and no loud clunk of the gas valve, you "might" have a PC board issue.

The board sends ignition signal through the hi tension wire. And the board sends the 12 volts to the ECO switch and the gas valve.

If the board has 12 volts going in the orange wire, means gas mode, and the safety circuit is working, the only thing left is the control board. It would be odd that both the gas valve and the igniter would die at the same time but not impossible. You can put a volt meter on the gas valve and ECO wiring and look for 12 volts but the gas valve makes a load clunk when they engage. You can hear it if you are outside and someone turns on the gas switch inside.

Atwood service centers should have a board tester to tell you if it is bad.

Hope this helps

John

13V on Orange wire from 'Gas' On/Off Switch to circuit board

So with gas switch ON
Check for DC Voltage on Brown wire (very bottom one---BRN 1 ) to thermal fuse ...to t-stat...and back to circuit board on brown wire (top one--BRN 3 )
This circuit MUST make up before DC Voltage can go to spark/gas valve

Thermal Fuse blows at 190*F...one time fuse
T-stat has to have DC Voltage to & thru it ---- water temp has to be below 110*F for it to CLOSE
Connectors need good contact on board

Then should have DC voltage on red wire (RED 4 ) to ECO then to Gas Valve solenoid

Check all grounds

Works on Electric ---same circuits(thermal fuse/t-stat/ECO etc
SO could be bad 'gas circuit' on board

It's a 2007 and the model is GC6AA-10E. I cleaned the terminals on the circuit board and I have 13 volts coming into the circuit board via the orange wire on the top plug

Can you post the model number of the heater? and what year it is? The controls have changed over the years.

On the "newer" Atwood's, the "same" electric controls run both gas and the electric element.

On the "older" Atwood's, the electric had separate controls and the gas had it's own.

Somewhere in the 2002 to late 2003, the new style came into play. And even on the older ones, there was a few generations. We need to know what model you have to help better.

What it sounds like in your case, is the safety circuit is not being made. And it sounds like you have the older version where the electric element controls are on the inside of the camper side of the heater and not outside compartment with the gas valve.

Make sure 12 volts is actually going to the control board as a starting place. I have not seen Atwood put a fuse on main power to the system but your camper mfg might have.

Common causes have been regardless of version, corrosion on the circuit board plug so the connections do not work. Remove the plug, clean and put the wire connection back on. Sometimes just unplugging and re-plugging a few times gets it going.

Corrosion on the high temp limit CO thermal disk switch terminals. This looks just like the thermostat just at a higher set point. But this only affect the gas valve, not the igniter.

Corrosion on the thermal fuse wiring if your vintage has the thermal fuse. This is for a fire or excess heat in the outside compartment. This is a very small thermal fuse that has a clear plastic cover over it. The connections on the ends get cruded up and the circuit will not make.

You will not get a fault light until the system actually try's to fire the igniter and the gas valve. The fault light is only for an ignition failure once the system try's to light. Since you hear no, thunk of the gas valve opening and no click, click, click of the igniter, you never made it past the safeties to allow the gas valve and igniter to start.

Hope this helps

John