Forced Air Natural gas Heater keeps cycling on and on

It sounds like you have a restriction in the ductwork ahead of the air cleaner. If the ducts are insulated on the inside it is likely that the insulation has come loose and is blocking the ducts. Remove the air cleaner and take a mirror and flashlight and look into the ductwork from the air cleaner back toward the return grills, and also check from the closest vent looking toward the airhandler. It is also possible that the heat exchanger is stopped up. How long has it been since the unit was thourghly cleaned?

Thanks for your information! I suspected something I jokingly called it a "racoon in vent" but nothing even smaller animals ever manages to get in. Interesting that there is something like insulation in those big square vents which can actually dislodge and block the vents! The ones I can see running across the ceiling in the garage (rest of house is 100% finished so no views are available), but I did remove a number of registers and as far as my camera can see down the vent they look open, but that is only a foot or so before they take sharp turns and who knows what is down there! I took a long vacuum hose down a few (mostly clean as we have electronic air cleaners for over 40 years) and I have a dryer vent thing with big whisks on the end but it too is only 3 feet long and lots of the system is totally in the dark as to what could be blocking the return duct.

In the meantime, I had finally chosen to have a tech come over and check it out and they told me stuff which is in my other questions on this site See my question: " Dirty AC Evaporator coil blocking air flow to nat gas forced air Heater---can I clean it myself? "for more information maybes that would help you in this discussion thread...

To directly answer your question you asked me, no, none of our service people ever mentioned that either our vents were dirty enough to be cleaned out, or the evaporator coil was getting caked with dirt over the years as no one ever bothered to look inside I guess until someone cut a hole in the side of the unit and looked in with a camera!

Thanks for your reply again!

"extremely puzzled"

A dirty evaporator coil will restrict air flow. A sign of that would be iceing in the cooling mode. A dirty blower wheel in the furnance will also restrict air flow. If I read the first part of your question correctly, you said the air conditioning worked properly which would indicate that not being the main reason for an air flow issue. 1. Where is the evaporator coil located in the system? I am assuming the air flow picks up when you remove the air cleaner since you said the heat works properly with it removed. If the eveporator is between the furnance and the air cleaner where it should be and was causing the problem, removing the air cleaner would not have any effect on the system. A good hvac technican should be able to isolate your problem in approx and hour or less by using checking the static pressures on the return and supply side of the system. Static pressures will show restrictions and air flow issues. I am still seeing indications of a restriction in the return duct or a possible colasped duct by your response.

Thanks for your reply stanhvac1 !

I have something called photobucket which works at this site very well, used it last year for another situation. I'm trying to post, but have to remember how. Will show you the Amana Air Command 80 with the Honeywell air cleaner at the left and on top of the Amana unit above the heat exchanger is the A framed evaporator coil in a black box since 1960. Above that are the ducts for the outgoing heater (or air conditioned) air. At the left before the Honeywell, all the returns combine to a huge 40x20 return before it enters the bottom of the Amana unit where the fan unit you mentioned is housed.

When a tech opened up the unit, the floor of the returns is spotless, got not a smudge of dirt on his jacket as I can reach through and vacuum it at least twice a year. The fan unit I cant clean, but upon removing it there was a few dirt balls, which I got rid of by hand.

The main problem seems to be the evaporator coil, and a camera view (see my follow up question here at Homeowners hub titled: " Dirty AC Evaporator coil blocking air flow to nat gas forced air Heater---can I clean it myself? "for more information maybes that would help you in this discussion thread...

That showed up on a flexible tube camera to be almost totally blocked off with dirt.

I hoped I described my arrangement better to you now.

If you still would want to see the photos of the units ... I can post them, let me know I'm still trying to do it anyway if I can remember how I did it last year. The tech who came by with the tube camera....said he can't make a copy of the photos from the tube camera---I think he can but didn't want to give it to me)

Oh, to answer your first question which I missed, no icing during the summer on the Air conditioner pipes (large or small) and this summer fully charged up the Freon as had lost some over last year due to the problem in another earlier posting.

Thanks for your reply again!

"extremely puzzled"

Thank you for bearing with me in trying to assist you. It is diffucult to isolate some issue's quickly without being able to see the system personally. I did read your other comment a few minutes ago on the dirty coil. Back in the 60's we did some stupid installs due to less knowledge than we now have. To answer your question of cleaning the coil, the only way it can be properly cleaned is to remove it from the furnace and wash it with coil cleaner. Regardless of what you have been told it can be done. I do it all the time and granted most of the time it requires extra work cutting it out of the box and making a new cover when reinstalling it.

1. Stupid install: The evaporator coil should never be downstream, (after the heat exchanger). It should be on the return side of the unit.
2. I will need you to picture this in your mind as I explain it. Let's think air flow since that seems to be the issue here. Please bear with me here as I am trying to get a picture in my mind of your situitation. First: if I understand correctly, everything works properly with the blower compartment cover and (or) the air cleaner removed which both are on the return side of the system. So the flow of air is through the blower to the heat exchanger to the evaporator coil and into the supply ducts. I am going to use a water circuit to demostrate this, see pitcure below. A. with valves 1,2and 4 open, valve 3 closed we will get 60 psi water (full air flow) through valve 4. If we close valve 4 (Totally blocked evaporator) no water comes out, (no air flow). Again, open valve 4 we get full flow. B. If we close valve 1 half way we will get 30 psi through valve 2 and 4, (restricted return). C. Leaving valve 1 half closed, valve 2 and 4 open (30 psi). Now we fully open valve 3, (remove the air cleaner or blower compartment door) we once again get 60 psi through valve 2 and 4. I hope I am not losing you onthis but this is the reasons that it appears to be a return side restriction verses a supply side restriction unless I am not reading your comments properly.Also, I would like to know the size of your air conditioner as a 40x20 return is good for 7000 cfm which would be a 5 to 6 ton air conditioner.