Late Sunday evening I became aware that the temperature in the house was yet again drifting below the accustomed setting. I checked the furnace and discovered it futilely running with no flame, blowing increasingly cold air throughout the house. I headed to our gas range, all the while fearing a repeat of our recent experience of running completely out of LP gas. Unlike a few weeks ago, the stove responded with a reassuring hiss and "whomp" as the miniature blue explosion indicated that all was well with the fuel tank.

I returned to the furnace, removed the grill and peered into the interior with little confidence that my limited knowledge of its operation would result in the house becoming cozy once again. Every time that I have experienced a furnace failure, I am amazed at the sense of desperation that it brings on. Neither the loss of electricity nor water pressure ever conjures images of equivalent disasters to pipes freezing, children huddling in the car for warmth, house plants and chicks dying as I stand impotently shivering in the ruins.

By powering the furnace down and back on again, I was able to observe what was happening. The pilot jet was properly igniting but the sparker continued to tick away as if it had failed to light. Thinking that the flame sensor (no longer a thermocouple, I later found) was dirty, I began tapping and scratching at the sensor rod.

By trial and error I realized that my fiddling was causing the sensor to momentarily recognize that the pilot was indeed lit, as indicated by the clicking of a relay. Before long, I had learned how to continue the charade long enough to convince the furnace electronics that it was safe to open the main burner valve and spin up the blower. Once lit, the furnace dutifully brought the house back up to a comfortable temperature before winking out yet again.

I kept this up throughout the night, waking every two hours to tickle the furnace into operating once more. In the morning, I contacted our furnace repair guy who happens to live about a mile away from us. Right away he diagnosed the problem as stemming from a clogged pilot orifice that was preventing the flame from being large and hot enough to be detected by the sensor.

For good measure, he replaced both the pilot assembly and the sensor. Unlike before, each time the furnace kicks on it now lights the pilot quickly and without fail. I can safely return to taking the warmth in the house for granted at least until the next time the thing breaks down and threatens to end our civilized existence.