I came here to be edumacated!

We bought this house that had a brand spanking new Ducane furnace, model 80G1DF. The unit runs continuously regardless of which position the thermostat is set (on/auto). On the cool cycle, when it calls for cooling, i can hear the unit outside kick on and cold air come through, but on heat, nothing happens (meaning the blower still runs, but there is no pre-purge, opening of the gas valve or ignition happening)

My research is pointing to a open limit switch, but the kicker is that the panel LED is not showing any faults. Its a steady on, indicating normal operation. I thought i would expect a 4 blink fault code.

Here's what i've done so far though:

- made sure the filter is new, and cleaned the general area (its new so there is really no dirt anywhere)
- checked for obvious loose connections
- tapped on the relays on the main control board to make sure that we don't have a stuck relay
- replaced the thermostat with two new ones.

I would appreciate any help or direction with this. The weather is getting cold and it would be nice to have the whole house system running instead of the electrical heaters we are using as backup. We are also limited to our budget, so like many this would be our last resort to make sure we understand the problem, find a possible/obvious solution and/or not be ripped off.

We kindly appreciate any help/suggestions that you can make.