new gas valve dead after 1 year--why?

The first winter in our new house, I discovered that the furnace wasn't working. Traced it to the gas valve, replaced it with a White Rogers 36H33-412 and the furnace worked great through the winter. Now one year later, I turned on the furnace for the first time this winter and found that the gas valve is again not working. What could cause a relatively new (<1 year old) valve to stop working over the course of ~8 months with no use? Gas and voltage go to the valve just fine, ignitor fires up, but no gas comes out from the valve to catch. Seems like it is stuck, but banging with a wrench didn't cause anything to become unstuck! Again, everything worked fine for a full winter after the new valve was installed. Any ideas would be greatly appreciated!

I'm in a warm and dry climate. Trane system is probably ~10 years old. Small house.

 

Welcome to the forums.

I can count the gas valves I've changed on one hand. They very rarely go bad.

Have you actually measured the 24vac ON the valve ?

 

Something must happen in dry climates. I've read a number of cases lately, all from AZ, about stuck gas valves.

 

Could it possibly be something carried in the gas ?

 

I would measure the inlet gas pressure to the gas valve (or have it measured)

The maximum gas pressure should be listed on the furnace. Probably 1/2 psi max.
I usually measure ~7.5" W.C. to 11" inlet pressure and 3.5" W.C outlet pressure.

28.7" water column = 1 psi.

I have seen underground gas piping partially fill with water.

 

There's certainly been plenty of rain down there this year and Southern AZ utilities don't have a real stellar reputation.

 

Thanks for the replies. I am getting 24V at the valve itself. Seems like there's a mix of opinions on how often the valves go bad. My setup does not include a sediment trap or drip leg; there is some flex line that forms a "U" before going into pipe that enters the box. I opened the line and gave it a shake and a few flakes of sediment came out. I'm now wondering how often control valves get clogged by sediment in the gas lines. Anyone have experience with this? Perhaps some sediment formed in the line during our 8+ month off-season and got pushed into the valve when I turned on the furnace for the first time this year.

 

It's probably worth measuring the inlet pressure before I put on another valve. Thanks.

 

I would most certainly have a drip leg installed.