[legion]

I had a similar problem for years. The problem got worse the colder it got. I had the furnace company at my house three times and got three different solutions (none of which fixed the problem).

The only difference is that I had a spark--it would just take from a few seconds to light to never lighting.

Turns out the problem was........a vacuum leak.

I have a side-vent furnace (a blower motor pushes the exhaust out a horizontal vent). There was a vacuum tube that ran from the blower motor to the flame box. The tube was fine, but the flame box was not properly sealed. I taped it up with silver tape and have not had a problem since.