I've been trying to help out my friend's mother. The problems started like this;
The heater was never producing enough heat to meet satisfy the thermostat on some of the colder nights out here. The heater would be on, but only produce cool air at the registers inside the house. The owner had a HVAC service company check it out and was told her thermostat did not match the type of unit the home was using, a gaspack unit is what I believe is the common term for the type of gas furnace/air condition unit she has.
They wanted to charge her $300 to replace it. I don't know if she misunderstood what they wanted to do, of if it's common to charge that much to install a simple t-stat. I got her a nice programmable thermostat and installed it the other night. The only one was wired in a way that didn't make any sense to me at all. I followed the instructions for the new t-stat, very straight forward, Green to G, White to W, Red to RH/RC, Yellow to Y (install guide said not to hook up the "C" wire to this t-stat.
The previous unit had them wired as follows; Red to R, Blue to C, Green to G, White to W2 (that was jumped to E as well) and Yellow to Y. Their was an orange wire hooked to the O/B terminal, but it was not actually hooked up to anything inside the unit.
When the old t-stat was hooked up, I don't believe the gas ever actually started to flow. With the new t-stat, I got ignition and the fan blew, but the air still didn't seem to get warm at the registers inside the house. The heater shut itself off after about 3 to 5 minutes and I got a blinking fault light inside the unit. The manual's trouble shooting guide give a few suggestions based on just the fault light, but I hope someone here has a little more light to shine on it based on everything else going on.