Atwood water heater ECO and temperature thermostat

Let me ask a couple questions.
Use an Ohm meter and measure the ECO and thermostat. Disconnect one of the brown wires. Measure for resistance between the contact and the other brown wire. Should read a direct short. Reconnect wire when done.
Next disconnect one red wire and test(ECO). Should read direct short.
Next adjacent to the ECO/thermostat is a piece of heat shrink tubing on the wire. Inside is a thermal fuse. Test it for continuity.
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Atwood t-stat (normal temp) controls the on/off firing of propane. It closes when water temp drops to 110*F allowing 12V DC to go thru ECO and to gas valve.
It OPENS to shut down propane firing at 140*F

The ECO t-stat (Energy Cut Off) is always CLOSED unless normal t-stat fails to OPEN and water temp goes HIGH.
It OPENS at 180*F shutting down propane firing and triggering the 'FAULT LIGHT'

IF ECO OPENS it will self reset when water temp drops below 150*F but 'Fault Light' can not be reset until switch is turned OFF then back ON.

Thermal Fuse (Clear tubing) connected to t-stat is a 'one time temp fuse'. IF it blows it has to be replaced. When it blows ALL 12V DC power is lost.....nothing will work until replaced.
It is a safety device that burns out at 190*F .....it is for flame blow-back out of combustion chamber/burner tube.


ECO and T-stat are both just snap disc devices BUT the terminal/spade connectors are different sizes. ECO larger. So the brown wires only fit the T-stat and the Red wires only fit on the ECO


ECO and T-stat connections need to be clean and tight
ECO and T-stat must be held tight against tank wall
12V DC goes to ECO and then to gas valve solenoids at same time High Voltage DC goes to spark electrode....DC will only remain on gas valve solenoids for 6-8 seconds unless main flame lights off and proves it lit via milivolt signal back to circuit board.


Normal T-stat (small terminals).......Opens at 140*F (controls firing and water temp between 110*F to 140*F)
ECO T-stat (larger terminals)..........Opens at 180*F (always closed unless temp goes too high)
Thermal Fuse (small terminals)........Burns out at 190*F (No DC for anything if it blows)

There is a nice troubleshooting info at "beamalarm.com

Old-Biscuit wrote:

ECO and T-stat are both just snap disc devices BUT the terminal/spade connectors are different sizes. ECO larger. So the brown wires only fit the T-stat and the Red wires only fit on the ECO.

I won't have access to the TT for another week, but I don't recall that. One of the replacements had a round terminal soldered to the one of the terminals.

Old-Biscuit wrote:
Normal T-stat (small terminals).......Opens at 140*F (controls firing and water temp between 110*F to 140*F)
ECO T-stat (larger terminals)..........Opens at 180*F (always closed unless temp goes too high)
Thermal Fuse (small terminals)........Burns out at 190*F (No DC for anything if it blows)

Good to know, but not exactly easy to test. I will have to get the tea kettle out !

The thermostat with the round wire terminal soldered to it is for the 16 gallon EXT water heater and is set for about 155 degrees. This is the wrong thermostat for a 6 gallon unit. You mentioned a kit that contained two identical looking thermostats. This is the kit you need. If you look at the back of the thermostats, one will say 60C and one will say 82C. The 82C is the ECO.

No need to redesign the engineering of attwood heater. Just buy the correct parts.
The only modification I do in all the Attwood 6 gal, is change out the 140 thermostat for a 120.

Just my own preference.

jetcare wrote:
The thermostat with the round wire terminal soldered to it is for the 16 gallon EXT water heater and is set for about 155 degrees. This is the wrong thermostat for a 6 gallon unit.

Thanks. That is what Camping World sold my son-in-law.

jetcare wrote:
You mentioned a kit that contained two identical looking thermostats. This is the kit you need. If you look at the back of the thermostats, one will say 62C and one will say 80C. The 80C is the ECO.

Anyone know the part number ?

You should be able to test the Thermal Fuse, Temp and ECO 'Stats with an ordinary meter. Disconnect their connectors so you don't get a false reading from something else in the circuit. JetCare's and OB's info should be enough for you to test those parts and determine if any of them is bad.
The Edge Connector from the ribbon cable to the logic board is a prime suspect on these Atwood water heaters! Clean the contacts on the board with a pencil eraser. Re-arch the springy contacts in the edge connector with a dentist's pick.
Be glad it's not a "Standing Pilot" LPG heater. If those are lit when not full of water, the ECO part of of the $100 thermostatic gas valve opens and it's a "One Time ECO." Valve has to be replaced.
Please reply with the Model Number. We may be able to help in more detail. Also, with that info, you can probably find a manual on www.bryantrv.com

First, thanks for all of the suggestion.

Second, I after re-reading my original post, I realize I did NOT describe the symptoms ! The water heater lights as soon as you turn it on, indicating that the ECO and thermostat switches, valve and ignition are all working. The problem occurs AFTER the water has been heated and it is cooling down.

The igniter comes on, indication that the thermostat switch has closed, but the burner does NOT ignite. I ASSUME this is because the ECO switch is open (ie. the gas vales are closed).

EDIT : I forgot to say, after trying to ignite and failing, the control board shuts everything down and light the "failed" light on the control panel. Of course, by the time you notice this the water is cold. If you cycle the power switch then, the burner DOES come on.

I will have to get a thermometer, some hot water and test each one with my DMM.

Clean the circuit board connector.
Clean the gas burner tube
Test the ECO and thermostat while in the water heater