The issue you are having with the atwood rv water heater part at96121 g6a 8e sounds like a faulty control board the replacement control panel for atwood water heaters part at91367.
Hot water heater control panel.
Water heater ignition control board.
In order to confirm this you will need to check for power on the wire that goes from the board to the eco or eco to gas solenoid while the igniter is clicking.
Reliance hot water heater gas control valve 100112336 9007884005 100093974 1 cavity thermostat compatible with reliance state a o.
I hope to find a place that rebuilds these.
Fits suburban water heaters.
Find water heater parts at lowe s today.
Smith and american branded heaters 4 4 out of 5 stars 163 129 00 129.
Taco zone valve controls the taco zone valve controls should be used in coordination with 2 3 or 4 wire zone valves.