I'm at work so I don't have the model or any part numbers, but wanted to see if anyone had an idea of what my problem might be. My furnace (15-20 years old, central gas heat) suddenly stopped working one day. No pilot light, no sound from blower, and no cycling. Found that power was going into the ignition control module/circuit board but none was going out. So I replaced that and now it cycles. I can hear gas come out, but all it does is click on, then 5 seconds later it clicks off. I can hold a flame under the flame sensor and the top row will light, but the four main tubes don't get ignited and after two seconds the furnace turns off gas and shuts off. The blower also never turns on. I checked all the connections and everything is fine. What can you suggest I do?