Simple explanation of the state I am observing. Thermostat clicks on to call for heat and immediately clicks off like it's satisfied. While in the "state" the main blower won't run when the switch is moved from auto to on. Initially when in this state the thermostat briefly displayed NO AC between the two clicks.
Now the Gremlin part! sorry for long post.
This state first occurred the w/e before T'sgiving. I check the breaker and then called and talked to the on call tech and he talked me into waiting for the regular work week to save some money. OK fine the downstairs heater was still running and it wasn't going to get that cold. Tech comes Tues. and goes upstairs to troubleshoot gets the unit running by bypassing something I guess and watches it cycle, tells me he believes the control board needs to be replaced, shows me what he says are some hotspots and as he is replacing he tugs on a wire in the main harness and the fan cuts out so he says we should probably replace the harness as well but he is not sure what the availability would be. Takes my $75 , tells me the board will be $650 and his boss will call later about the harness. Boss calls $525 for the harness 7-10 days delivery or we could put in a new furnace for $3200. The thing is the heater has been running for the last 6 hours. I get nervous replacing two things to fix one problem so I take it under advisement.
Heater runs until Saturday and then the state returns, click, click etc. I shut it off and figure I'll call for repair Monday. Sunday on a whim I turn it back on and it starts running again! Now for some reason I get the idea to swap out my thermostats, I'm sure the tech would have suggested replacing if he thought that was the problem but the upstairs and downstairs thermostats are identical so I swap them out power up and both units start running. I cross my figures and hope the d'stairs unit starts acting up so I'm only out a couple hundred bucks for a T'stat instead of $1200 that I'm looking at.
Now both units keep running and running and even though I did not see anything wrong I begin to think maybe there was a bad connection on the upstairs T'stat. Nope, early Christmas morning as I'm waking up, click-click, click-click, crap tell everyone that they will have to bundle up when we go to bed tonight. Next day I get the idea to go up and jiggle the wiring harness just to see if maybe I can get the furnace to run. Well on my way up to the attic I switch the T'stat to on and .... you guessed it, the unit starts running and has been running since! What gives???
I've worked most of my life in large manufacturing plants, around digitally controlled boilers, furnaces, refrigeration units and lots of other stuff and never run up against anything like this.
Any help would be greatly appreciated the thought of laying out $1200 and not knowing whether the thing will be fixed is giving me a knot in my stomach
Thanks and happy Holidays