I seem to have a difficult to diagnose or explain problem with the Main House Heater Unit:
It is an Amana Air Command 80 (c 1986 mfg date).
This started sometime last winter heating season (2012-2013) but took so long to figure out that there was "something " going on that the season was over and we just figured it might be due to warmer than usual winter here.... or whatever...
But its been so long since I've seen a "normal" cycle of Heat from this Furnace that I can't for the life of me remember it properly.
I seem to recall that a Heater goes on with flame....heats up heat exchanger....then the fan comes on and blows it around the house.....flame goes off and fan runs until its too cool for use then it closes down
Then cycle begins again!
What happens last year and this heating season (did not occur with the Air conditioning cycle this summer) is that the thermostat says calls for Heat.
Then the flame goes on
then it heats up the heat exchanger tubes
the fan comes on and blows and flame goes off as its supposed to
but then the thermostat?? or maybe its the computer board onboard the Amana Furnance that is now calling for MORE heat while the fan is still running, blowing the old series of heat!!
And the crystal lights the flame----but suddenly the Thermostat or the Heater "wakes up" and says the fan has already done its job, so it turns off the fan while the new series of heat is working to heat the coils.
Then after the exchanger is hot again something tells it that well we'd better turn on the fan to move this new heat around the house
and on and on it goes.. re cycling the process "shorter" heat cycles and more and more fan on and off cycles
This can't be good for the crystal starter element--
or the FAN going multiples times on and off and on and off......
and its certainly hot enough as the thermostat does not turn off "early" its just running spending more gas money spent running the heater before the fan has completed its job!!!
So far I investigated a few things with some local help (who is puzzled and can't fix what is not "broke")
I found the "fan limit" switch cycles from 100 deg set point to its 200 deg upper limit within a few minutes of the gas jets turning on. Then as a safety feature (I just discovered) it turns off the flame and keeps the fan running. I watched while the fan limit (and it bi-metallic probe in the heat exchanger) rapidly cooled down and then once its below 150 degrees the thermostat which is not satisfied yet, calls for more heat and the cycle repeats over and over again. Thus the house heats up very very slowly doing this cycling method.
Again someone helping figured maybe there is a vent blocked in the registers or return ducts. I opened up a few ducts since then and found almost zero dust, just clinging to the sides of the duct leaving 99% open and free for air to move. Now I also have an Honeywell Electronic air cleaner mounted at the final section (largest) return ducts just before they enter the Amana Furnace. Its been there 30 years with one or two models before that! Everything worked fine.
But mysteriously when I had the "cover" off the Honeywell air cleaner, the system WORKED PERFECTLY!
Now before you say "dirty filters" as an answer, we just washed the entire unit (not that regularly but it was washed in dishwasher as required before the winter season started) and we got a brand new set of pre-filter screens too---I even switched back to the older screens for testing (both made of metal you wash them....but older one had more holes) which I got specifically to wash them more often (but this is before the unit came on again this winter heating season with the same mysterious defect.
One other thing (I could send some photos as I did to this site on a question last year, if you want to see it) the person who installed the Amana 30 years ago, with the existing Honeywell back then cut TWO additional vent holes and covered with decorative vent covers right on the final return before the Honeywell (so there has been always two huge gulping air vents taking the cooler air from the HVAC room back upstairs to recycle it a bit from the downstairs areas.
Just weird that only by opening the cover door to the Honeywell (don't have to remove the unit! but it helps to give it more return air) the Amana and Thermostat and everything and heat limit switch all works perfectly!
I make jokes...I said aha! Racoon in the vent! but its not able to do that and we've never had anything in the vent systems and all registers that I could remove with a screwdriver and vacuum (and got a long long dryer vent scrubber too) are cleaned now spotlessly....
Yet still frustrated by this condition. Before we call in others who will just sit there spending money investigating (as one person said scratching their head who came that they had no idea where to begin once I showed them the Honeywell door open and everything working!), has anyone out there heard of a problem like this? Googling the answer I can't get close to it as I'm certainly not a HVAC person and not using the right/correct terms to locate anything on the web.
Thanks for reading this very long explanation!
(sorry for the "" marks I can't edit them out they do not appear on the edit page!)