From Burkes posts:

I had a service tech at my house about 2 weeks ago after my furnace started acting up and he didn't find anything wrong with it - cleaned the flame sensor, burners, made sure the drain was open, and billed me an hour of mostly head scratching. Since the furnace was cold that day it ran just fine whenever he tried...

I'd like to hear some suggestions as to what to do next to determine what's possibly broken, so I can determine if it's time to buy a new unit or pay for whatever it takes to make the thing work again. I'd like to avoid getting a new furnace for a year or two since I want to add on to the house and I may need to get a different size furnace at that stage anyway.

I don't know how you can say;

"think i missed something here are you doing the repair because we can not possibly tell you what to do to fix this problem. we can give ideas and thoughts about it."

this whole business of clammin up when a homeowner dares to ask a question about doing things to their furnace that the very manual from the manufacturer says they should do amazes me. Yes, it is not supposed to be a step by step instruction site. Let Bob Villa do that. I for one, more often than not, end up referring the customer to a qualified service company rather than do it themselves.

This guy is operating and monitoring his unit, which is not working as it should but is not old enough for the scrap heap. And he is posting questions here to understand the operation and be prepared for the technician when he returns.

That's the way I read it. Unfortunately, a solution has not yet been found. I think a tech is going to have to dismantle the unit a bit and do some exploring. (Scapel)