I have a Coleman Evcon model # dgat070bdd that is'nt working. When I kick up the thermostat, a fan kicks in (combustion air fan),it runs for aprox. 60 sec. than there is a click followed shortly by a thunk from the gas valve. After a bit, the gas valve thunk again, shortly after that the whole thing shuts down. There is trouble code light at all, steady or flashing. I assume that I should be able to see an ignitor of some type through the small window under the gas valve. Nothing glows or sparks in there. What could the problem be?

Sounds like a bad hot surface igniter. You should see the igniter glow orange, if not, then it is bad.

Thaks. I'll give that a try.

I have a Coleman Evcon model no. DGRT070AUB furnace that the pilot will light, the thermostat will click, and you'll hear the furnace click, like the gas valve will activate, the flame will increase some but no for long, and the fan motor never does run and no heat.