Furnace Problem

[Parker]

I have an ArmStrong Ultra SX 80 gas furnace. It seems that it was installed in 1997. This furnace has the Honeywell Smart gas valve. Not long after I moved in this house two years ago it started to have a problem: The burner would not fire, or the burner went out after it worked properly for a while. But it was not happening very frequently: once a few days, or so. And I could turn the thermostat off and then turn it on after few minutes and it would work properly again. The problem has been happening more often since then. In these days, it almost cannot fire the burner at all or the burners go out every time very soon after the burners are on. What I can tell is this: some seconds after the thermostat is on, the draft fan(is it correct?) comes on, then many seconds later the igniter comes on, sometimes the burners will light, but they can go off very soon(it can be less than a second to many minutes or 1 hour). After the burners go out, the big fan will be still on(if it is turned on because the burners have been on for some seconds) and the pilot is still on, but there is no heat(since the burners go out). Today, I replaced the igniter/flame sensor(they are in one part, and expensive), it did not solve the problem. I checked the small hose from the draft fan to a kind of switch, and found that it was not clogged. What else could it be? The “smart gas valve”? The control panel? Or I got a bad igniter/flame sensor again? Or ???

Any inputs will be greatly appreciated.


(-_-)

[Bob R]

I had the same problem in that the burners would not stay lit. I discovered I had a second filter between the furnace and supply duct. This second filter looked like it had been there since the house was built in 1984 and it was completely blocked with dirt. I changed this filter and that solved the problem. The burners work properly and the house stays at the temperature as set on the thermostat. The volume of air going to the rooms is also greater.