Can someone give me some ideas on what might be wrong with my heater? I thought it was the thermostate... I changed it and thought it was fixed because the it kicked on and ignited so I set it and had to leave the house when I came back the thing was still running the piolit was still lite but it was blowing cold air and the temp had dropped in the house

Take a minute of you time to help us help you.

The EXACT brand and model numbers go a long way in helping us understand just what kind of equipment you are having a problem with.

The type of fuel is also important information to pass along in your post. Natural gas, Propane, Heat Pump System's with or without an Electric furnace or Gas and Heat pump combo (Dual Fuel) and weather or not the unit is two piece (split system) with one section inside and the other outside or if it all resides outside (Package unit).

In most cases the time you spend telling us about your equipment will pay off in quicker and better answers which will better serve you.

There are many extremely talented people with a vast number of years in this industry on this board that try to help you. Please understand that since we are actually not looking at your equipment On Site we have a large handicap to try and overcome and the more information you supply us the better the diagnosis will be.

In some cases we may not be able to help at all. Extremely complex issues may have to be dealt with by a local HVAC service company since as mentioned before we are limited by the fact that we are not there to actually see and test the unit to come to a professional conclusion.

Thank you