I have an older Lennox furnace, it has been working fine, we changed the filters and got it ready for winter as usual, however after a couple of hours of it running warm and wonderful it started blowing cold air. I relit the pilot light as the mfg suggested, and like magic it relit and stayed lit with no problem. It ran for 4 days without a problem, but then the pilot was out again. It is vented through our chimney, (about 16 years ago) is this a problem with windy days? It never was a problem the last 7 years. Someone said it could be the pilot cell?????