Gas and Oil Home Heating Furnaces - Heat won't kick on at proper temp

We have a Lenox model #G2103-80-2 gas heater. It's about 13yrs old. We have a 3 floor cape. Unfinished basement, street level, and upstairs. Sunday morning woke up to a cold house (60 according to thermostat). I turned the heat on and off from the thermostat and got the heat to kick on. When my wife woke up, it was still cold and she called me at work. I work at Home Depot and conferred with some guys who work in Plumbing and they said it could be thermostat. I bought a Honeywell manual and hooked it up during my lunch break. We still have problems though. The temp continues to go down to 60 (it actually feels colder)before the heat decides to kick on. What's more, the house doesn't meet the desired temp before it kicks off. I spoke with Honeywell and they said to set the heat anticipator setting at .4 and leave it for at least 24 hrs. They went on to say that it takes at least 24 hrs. for the thermostat to "settle in". Sounds like a crock of waste to me. Any feedback would be greatly appreciated. Thank You, Walter Garner.

I dont know why when a furnace dont come on the first thing people do is run out and buy a new tstat for it.

If you pull R and W off the tstat and put together does the furnace come on right away??? This should tell you if its the tstat or not. ED;)

It almost sounds like it's locking out on you.

The model looks like a Lennox Pulse Furnace.

Are you the orginal owner of the furnace? If so, have you had it inspected, pipe stand cleaned, flappers replaced and heat exchanger pressure tested?

Lennox Pulse had a bad run of heat exchangers, and it failed due to cracks.

So, if you haven't had it tested at all, I would call in a Lennox dealer and have it done.