Your Atwood G6A-8E is a Gas only 6 gallon water heater with electronic ignition
S/B a simple On/Off switch with Light to turn it ON
Similar to this switch
Temperature control is via a Fix Temp T-stat....Opens at 140*F and Closes at 110*F for reheat cycle
ECO (Energy Cut Off...HI Temp t-stat) trips open at 180*F/resets at 150*F but if it trips it 'Locks-Out' water heater controls/triggers that RED Fault Light on switch
**To reset controls...turn switch Off then back ON
**If ECO trips...the T-stat has failed
There is also a Thermal Fuse that blows if exposed to 190*F
It is inside the Clear tubing and connects between Circuit Board and T-stat (Brown Wires)
Blows if Flame Blow-Back occurs from burner tube/combustion chamber
Atwood T-stat/ECO... (standard 140*F/180*F set)
Part #91447
Atwood OPTIONAL T-stat...(130*F T-stat)
Part #91470
Atwood OPTIONAL Adjustable T-stat....(110*F-150*F)
Part #93105
All the Atwood T-stats are listed here
https://pdxrvwholesale.com/products/...t-140-91447%20
12VDC Wiring Diagram that includes your Model