In the past week, the furnace would not maintain 70 deg. It will maintain 70 and below and 80 and above. However would not operate in the range of 70-80. If I push it past 80 it would work.

I talked to a friend that is HVAC tech. He stated that it sounded like a bad thermostat. I agreeded based on the fact that it was an extremely old and not very sturdy one. It was replaced with Honeywell Pro 8000 (8320). In the past two days since. The furnace struggles to maintain temprature. It is cycling off and on every 2-3 minutes. The thermostat during this time states "wait".

While the furnace cycles, there is no code indicated by the LED.

Here is what I DO know. I can place the fan on from the thermostat and the furnace will run until it makes temprature. Only when I have the fan selected from the thermostat placed in "auto" does the furnace cycle every 2-3 minutes.

The Furnace is a Coleman Evcon, I'm trying to determine if the problem is a temprature switch of if it is a circuit board. Any thoughts would be most helpful.

Of course the beauty of the whole thing is that the temps outside have only been in the teens the last week. I have it currently functioning with the fan set to come on as soon as the furnace comes on and it seems to be working.

Thanks!:(

I have the same problem and had a tech come in and he said it was my fan switch needed replaced but moments later said oh it doesn't matter as your furnace has a crack in the gas combustion chamber and now you need a new furnace!

You need to revisit the thermostat install and go over all the program settings.