Hoping for help here. I recently had my ignitor replaced. Before that, the furnace wasn't working at all. Now it starts blowing warm (not hot) air, then gradually over a period of a couple of hours, the air cools down until it is completely cold and the temperature in the house drops drastically. The repairman who installed the ignitor advised me to reset a switch on the side of the furnace when this happens... turn it off and then on again. This works as a temporary fix, then in a couple more hours, cold air again. It seems no one is interested in fixing my furnace, only in selling me a new one, although not a single person has been able to tell me exactly what is wrong and how much it would cost to fix it. I don't have any knowledge in this area but I also don't want to spend thousands that I don't have on a new furnace if it's not necessary. Please help! I just want to make a well-informed decision.

There could be a few different things wrong it could be a dirty sensor a drain could be plugged to name a couple you should call a dealer that services that brand and have them take a look at it

More info,, what is brand,, how old? is it coding at the control board?has it a clean filter? Is the blower slowing down and maybe quit running, After running a while.maybe we can help.

Like hixton said there are several things that can cause this to happen, one of the things that can cause it but is overlooked so often and that is a dirty air conditioning evaporator coil. If the coil is dirty the unit will turn off by way of the limit switch, in a few minutes it will cool and the limit will close again and the unit will come on then the whole things happens again. It will do this three or four times and then the logic board will put it into lock out mode and it will stay that way for several hours. But if you turn off the power to the unit, (like turning off the switch one the furnace) this will reset the logic board and the whole thing will start over again.

I am not saying that this is you problem, I just know that it does happen and is almost always over looked. Good Luck.

In response to wmproop's questions, my furnace is an Amana from 1992. I did change the air filter but the service man who was here to change the ignitor cleaned out the furnace also, which he said was quite dirty. Also, the blower never stops pumping out air, whether it is warm or cold. :eek:

I forgot to say, I will check to see if the control board is coding when I go home. I don't have a computer there so I'm at a friend's right now to try to gather info. Another question: if it is a dirty coil, would the blower go on and off? And would the air temperature go from warm to cold and back to warm again, like cycling? Because like I said, the fan never stops... it gradually loses heat and once it goes cold it never gets warm again unless I reset the switch on the side of the furnace. By the way, I really appreciate all of your efforts to help me. I'll check in again tomorrow to see if you have any more thoughts.

Cleaning out the furnace has nothing to do with cleaning out the Evaporator coil, and this will make the furnace blow cold air.