I have a Goodman single stage, LP converted furnace that was installed when my home was built (10 months ago). I checked to make sure it worked when we did our final home inspection. It fired up just fine. We live in Florida, and don't need the furnace that often. Therefore, I'm assuming that the problem with the furnace has always existed. We just haven't noticed it until a few weeks ago when we've really needed to use the furnace daily (its been 20 degrees outside at night lately).

The furnace won't fire. Since it is under warrantee I called an area HVAC guy that Goodman has listed on their website as a dealer/repair agent. I helped him perform all of his tests on the furnace. It passed them all w/ flying colors. Every check/test that occurs doing startup was receiving proper voltage. The gas line had the proper pressure. The final check was the voltage to the Gas Valve itself. Everything works fine, the glow plug lights up, and sure enough, the gas valve got over 24 volts. Despite this, there is no smell of liquid propane, and no flame. The HVAC guy said that it had to be a bad gas valve. After all, it was getting the proper voltage, but wasn't opening. I couldn't see anything wrong w/ his logic, until...

It happened again a few days later. Same symptoms, same method of diagnosing the problem. The Gas Valve was replaced again. The furnace fired like a champ, precisely two times. Of course by this time the HVAC guy was long gone. Now I'm getting the same symptoms. As I now know the guts of that thing fairly well, I skipped all other tests and checked voltage to the gas valve during the start cycle. I can hear it audibly click, followed by 27 volts on my meter, yet no LP.

I looked up the documentation on the gas valve itself. I gave a couple of twists to the inlet pressure tap, LP starts audibly seeping out, followed by that wonderful smell. I tightened the inlet tap and tried the startup cycle w/ the outlet pressure tap loosened and my nose and finger right up to it. I hear the valve click, as it gets the proper voltage, and nothing happens. No gas, no smell. I also checked the pressure regulator to make sure it had an LP spring, which it did. I have no doubt (in my inexperienced mind) that the gas valve is not opening, despite it getting the proper voltage. This makes the third in less than a month that has "gone bad"

My question. What on earth is making these things not work? Is there some fail safe thingie that I'm missing that can keep these valves from opening despite receiving the proper voltage? If not, what could make them consistently go bad? It's on a dedicated 15 amp circuit. I haven't had a breaker trip in 10 months. The board on the furnace isn't fried. It has proper voltage to all wires running through it. Please Help, my fingers are freezing off as I type this.

Just a guess, sounds like a possible pressure regulator valve sticking,or control valve sticking. Since you say 20° maybe moisture is freezing in the control valve.

I would try to go safety by safety wiring them together to simulate a complete circuit. And try each one to see if it fires and keeps running. It has to be a safety switch. I don't think you are going to get two dad gas values in a row.
Good luck.

Did he check the outlet pressure when the valve opens?

I would like to know the answer to what Rick asked. You said all the pressures are OK but I am interested in exactly what the inlet and outlet pressures are, after all, you should have no outlet pressure if the valve is not opening.

I have a Armstrong air teck 91 electric /gas furnace with attached AC it is averaging outside about 0 to -20 and just in the last 3 to 4 weeks we are getting a flatulence smell when the heater starts up and when it goes off, actually it could be the entire time but it isn't noticed till it kicks on and then lingers for a bit when it goes off. THe system doesn't look particularly dirty but hey I can't get into it to see too much but this has not been the case last year and it functions great. It is not the burning synging smell you sometimes get when you first use the furnace that season. Got any Ideas. Dead animal? If so how do you remove? Anything I'm really wondering.

Northerheat was right on in his question to you... What was the exact in coming gas pressure and outlet pressure to your unit? As taken at the gas valve test ports? You could be getting a creep by the primary LP gas regulator, where it leaks by LP gas until you have high pressure at the gas valve, and at the point of firing the burners it will not open. Have your gas supplier do a "lock-up" test to see if that is your problem... (bleed of gas past the regulator)