I'm not having any problems right now. I have lived in the house for about 7 years and never done anything but change the filter. I decided I should get the furnace checked out to be safe. I called a local HVAC outfit and asked them to come out and give it a once over. I was incredibly discouraged by what they did. The guy took a vacuum cleaner and removed a few cobwebs and dust bunnies. Then he held a remote CO sensor near the burner (no CO) and then he left. I asked him "aren't you going to check the various safety functions on the unit?" He told me if they weren't working then the furnace wouldn't work.
I had hoped for a more thorough check out. So I am hoping to get a service manual in case anything does go wrong I can have a guide to help me out.