[iwanttofixit]

I have a 9-1/2 year old A.O. Smith 50 gallon natural gas water heater, Model FDV 50 216, S/N MK02-2006490-216. A couple of years ago a plumber was doing some other work, and when he re-lit the water heater pilot light, something changed. Ever since then, on windy days the pilot light blows out--it didn't used to do that. I think he may have bent the pilot light shroud or damaged the thermocouple, but it's pretty hard to lay on the floor and see how things are lining up in there. During windy periods, like now, I end up lighting the pilot light about once a day. When it's not windy, it can stay lit for 4 months. This heater is in the basement and vents out the upper wall through a double pipe--exhaust out the middle and intake air in the outer ring. The metal shroud outside looks to be in good shape (not rusted out), and I tried propping a wind block, but it hasn't helped. Today, for the first time, the main burner didn't want to light after I lit the pilot, waited 90 seconds, and turned on the burner. The burner would try to light and go out, putting the pilot out, too. This happened twice. What causes this? I'm thinking about buying a new pilot/thermocouple assembly and trying to install it, but now I'm wondering if the heater is going out when the burner tries to relight, and that could be the gas control on the outside of the heater? Your thoughts would be greatly appreciated. Thank you.