Can you give me some info on troubleshooting A Quatro furnace with a Smart Valve 9501? I've checked everything that's easy as I'm an electrician but have no idea how to check the gas valve or the control module. The diagnostic light on the module says that it is working properly. Here is what is happening: the combustion fan runs, the igniter glows like it should and the limit switches work along with the transformer. I'm guessing it's the gas valve but hate to run out & buy one if that's not it. How much are they anyway?