This will be our second fall/winter in this house and our Armstrong SX 80 furnace with a Honeywell smartvalve ignition system will not light. The ignition switch will come on, but no gas is being emitted so the main burners will not light. I have seen this before where the sensor is bad after the burners come on, but the burners never come on.

The main blower goes, I have checked the wires that feed in to the control portion of the Smartvalve, but cannot get any gas to flow.

Any ideas?

May be a silly question,but are you sure the gas is on?, also at the time igniter comes on can you hear a click coming from the gas valve? Indicating that there is power going to the gas valve?

The gas is on because our water heater is right next to the furnace with the same supply and it is working like a champ, knock on wood. You are right, there is no click coming from the gas valve

We had similar problem. For two winters, the igniter would come on but not the burners. This was intermittent, sometimes the burners would come on fine. This past January it got worse. First time repairman came out, claimed was just dirty and hose to pressure switch clogged. Worked OK for a day, then intermittently working again. Then he said pressure switch bad, so we replaced it. That didn't fix it. Replaced the fan and igniter, on our own, didn't fix. Finally called another company recommended to us, the gas valve was not opening all the way, enough for the igniter but not enough for the burners. Replaced ($500) and working perfectly now. Finally.