Gas and Oil Home Heating Furnaces - Thermostat replacement

Can you tell me how hard it is to replace the thermostat. Do I have to rewire it through the house to the outside unit, or just replace the unit in the house. My heater quits putting out heat when the in-room temperature gets within 5 degrees of the temp. set on the tstat. It won't go all the way up to the set temperature, and it does not shut itself off, but blows unheated air continually, instead. Please help. Thanks!

Originally posted by Ed Imeduc
You use the same wires. Turn the power off to your units first so you wont short out the transformer.Take the old one off and put the new one on. Make sure you keep all the same color wires the same on the new one. That cool air could be you blower control,are do you have your fan set to on???? you dont say ht & AC heatpump elec or gas furnace here.;) ED
Also it could just be your heat anticipator not set right and the t-stat not level on the wall??

Thanks for the info. It is an AC/HT electric unit. Am I right in assuming that it can't be the heat pump if I am getting heat part of the time? How can I check the heat anticipator? I have the fan set on "auto", not "on", and it will turn off if I move the temperature on the tstat below the room temperature, but it will not shut off if the temperature is set higher that the room temp.

Now we have more.It sounds like your compressor is not comeing on for heat,or the 4 way valve is not working out side ,or your low on gas.Id say from here you have more than the t-stat to look at. With the fan in auto an you run the t-stat up the fan comes on and you run it down the fan goes off I say I half way think we have to look for other things that dont work.Or all the fuses or breakers ok and on for the outside unit???i think you should call a HVAC person in to take a look see at it ;) ED

How can I check the 4-way valve and the compressor. I don't seem to be getting any heat at all today. I have checked all of the fuses and breakers and they seem to be fine. I know I should probably call an HVAC tech, but I can't really afford it right now and am really hoping to be able to work this out without it.

At this point i would say call a HVAC person.you could be just low on gas or the valve bad and why your electric back up dont come on for you.The compressor can stop . You have a lot of things that can be down here right now that have to be looked at and i dont think its the t-stat ED;)

Sorry to sound so uninformed, but what would the gas be for on an electric heater. How would I check it and the valve? Thanks for all the info, Ed.

Sorry about that gas. When i said gas "HVAC "mean the freon that is in the unit.Like here in your unit it would be freon 22. The gas in your car if new would be #134. Now that is what got you cool when the AC ran this summer. This is also what will put out heat from your heat pump this winter. You have to be EPA Lic.to go in to the gas end on this unit.The electric furnace is like a back up for the heatpump and it will come on if the unit has to go into a defrost so it dont blow cool air. Hope the helps.Think of your heat pump as a window ac unit ok. Now when it gets cold outside and you want heat inside. You pull the unit out of the window and just turn it around and put it back into the window.Now the coil that was taking the heat out of your home and blow it outside is now taking heat what is there from the outside and blowing it into your home.This is all done with the 4 way valve i talked about.So you see why i said call the HVAC man it can be just a little thing and could be a big thing ;) ED

Thanks again, Ed, for all the info. At least I have a better idea of where to begin.