Pull the red wire and black wire off of each gas valve solenoid
(One solenoid at a time so you can install wires back on correctly ----solenoids are 'polarity' sensitive in that you can not cross wires and have it work)
With your analog meter set to X100
Touch red probe to solenoid terminal where red wire connects
Touch black probe to solenoid terminal where black wire connects
This will measure resistance thru coil.....S/B 40-50 ohms
Each solenoid MUST operate for gas valve to open
Circuit Board MUST receive Flame Proof signal to hold DC on solenoids (until t-stat opens)
Gas valve solenoids can be replaced vs replacing gas control valve
Atwood/Hydroflame offers a replacement coil- part number 31000 (replaces old part number 33475) for the White Rogers valve (Which is used by both Suburban and Atwood)
https://pdxrvwholesale.com/products/atwood-hydroflame-furnace-gas-valve-replacement-coil-31000
