I have modual shut down of a w-r 50e47-174 modual I cleaned the flame sensor & it works about 2 days to a week before failing. After turning the power off & back on the unit works fine for a short time. How do you test the flame sensor & what volt output Thanks Theo

Its all in millivolts. Make sure your gas valve and ignition control has a good ground.

LOOK here

http://www.white-rodgers.com/wrdhom/pdfs/06_Cat_pages/Cat_06_pg0278_281.pdf