Hi, my gas heating system will not stay on, here is the problem
-hear a motor, then the gas coming on/burners lighting
-fan comes on, heat starts blowing out after a minute or so
-heat runs 5-6 minutes
-air coming out of vent gets cold, fan shuts off after about a minute
-after shutting off, I hear a humming noise like a motor
-I hear the burners light and the furnace come on again, fan comes back on, and about 30 seconds later it starts back blowing out hot air
then, after running around 5 minutes more, it shuts off for good. It used to come on and run however long it needed to, but suddenly started this one afternoon a couple of weeks ago. The heat is and always has been VERY warm, and this has been a very good unit. I have no idea on an age or even make, all there is on it is a warning sticker, but I would guess it's around 15 years old. This is my third winter in this house and I know really nothing about the history of the unit. The filter is clean and I don't know of any airflow that is blocked. I am calling someone out on Monday. There was some sort of board replaced in the blower/fan a couple of years ago that I understand was connected to the heat also, but I don't remember what it was called- this was in the summer when the fan wouldn't stay on. The unit works properly but just doesn't stay on long enough and has to fire back up immediately after. It can only heat for about 7-8 minutes at a time without doing the off/on thing. It has not been serviced recently...I know, that's not good, but I can't change the past...
Is there any hope for it? I hope I don't have to get a new unit, I can absolutely not afford one
I am just curious about what could be wrong. I have gone through everything I can possibly think to do without having to call someone out. I am thinking the limit switch might be dead or something? Trying not to sound so stupid so I know what all to say when the technician comes. Thanks.