I replaced the air filters (something I hadn't gotten around to doing since we moved in) and that seemed to do the trick. Temp went right up to 68 and stayed there for a while. Then it went back down to 65. I played around a bit with the furnace and the OK LED light is giving me the "Open Limit Switch" code. I assume this means I need to close the limit switch although I don't know how I go about doing that. I have been all over the web reading forums and I am glad to learn that I am not the only one having this sort of problem. Any advice on how I close the limit switch? I think I have identified what it is, that's step one for me, but it doesn't readily look like something that is open or closed.
Thanks for your help.
The filters were beyond dirty. Solid gray with dirt, dust, and whatever else. I bet they haven't been replaced in over a year. Considering they are 30 day filters, they were well past their prime.
The furnace worked all yesterday afternoon and all last night...maintaining 68 and 62 degrees respectively. Then when I got up this morning, 60. Shoot! Here I thought I was Mr. DIY Fix-It-Man! So I took your advice Tammyngabe and diconnected the flame sensor. Since the yellow flame LED was blinking you hit the nail right on the head with that suggestion. I cleaned it up with a little steel wool and wouldn't you know it? Solid yellow LED now, the burners stay on, and the temp is up to 64 already! Sweet!
I hope this does the trick. Thanks for your help!!!