Just went through a 3 week long ordeal with my barely 5 year old Lennox furnace.....I noticed it was not coming on at random times when the tstat called for heat. Checked all the usual suspects, couldn't find anything wrong and just wrote it off as a fluke occurrence (only happened two times over the course of two weeks). Then it started to get more frequent, but thankfully it was still warm outside (40-50 degrees). We have an annual service plan so I put in a service call (no charge). Tech #1 comes out and checks all the same easy stuff as I did and says he can't find anything wrong (problem was very intermittent and I couldn't "force" it to fault, either). Day later, happens again, so same tech comes back out, does some more checking and turns the fan speed up a tad thinking it may be going off on overheat, says call back if that doesn't fix it. It doesn't. Tech #2 now comes out, spends about 3 hours and still can't find anything wrong. Then he says to replace the circuit board as it may be bad......$260 part (not covered under service plan, but I agreed). Swaps board, everything runs great, he leaves. Next day, it craps out again. I install a new tstat on the wall just for giggles, doesn't fix it either. Tech #3 comes out, says he's the tech they send when no one else can figure something out. Nice guy, burned out hippie type, but knows his stuff. Cuts a huge gash in his hand while working on the unit and informs me he's a hemophiliac, and asks me for a bandaid....I gave him half a box. Eventually he diagnoses it as a bad flame sensor, and replaces it (part covered under plan), and I've had heat ever since.
All told, I lost about 2.5 days of work total, but it was worth it now considering it was -1 here last night. I still have the old circuit board (they offered to put it back in and take the new one back for credit), but I figured it would be best to just keep the old one as a (working) backup spare JIC the new one shits the bed at o-dark-thirty some cold winter night.
Jeff
