Bryant Furnace Not Igniting

[feritayl]

We had a Bryant UpFlow furnace installed 3 years ago and have had an intermitant problem from the beginning. When the thermostat calls for heat the outside vent fan immediately goes on but the ignition coil does not glow nor does the internal vent fan. When I open the blower door all goes well. As soon as I close it everything shuts down except the exterior vent fan. Most of the time the system works fine and always works when the service tech is here. It's never pulled a code and removing the filter doesn't help. Of course the problem only occurs on the coldest days. The dealer was stumped when it was under warranty and now at $58/hr. is more than happy to visit, clean something, and feel good about charging me for not fixing the problem.
Thanks for your help,
Brian