I have not seen any codes - just a blinking light (seems to blink slowly 3 times then rapidly 3 times - then repeat) Furnace will not start without me flipping the switch on the side- the one next to the round fuse. It will work okay for an hour or so and then do it again. Any ideas? It has done that thing where it will start and stop repeatidly for a long time - I had it serviced in October - told the guys about it and they said something about the front panel needing to be seated correctly - it continued to do this after they left.

There is a safety switch on the front panel to keep carbon monoxide from being sucked into the unit. If they left the panel loose they did not do their job and you should be raising hell about it to the owner of the company because it can kill you. Further, if they did not clean the AC coils and left them dirty they did not do their job there either. If the airflow is down due to blocked coils another safety will open. If your unit is more than two years old and you do not have a HEPA filter (6-8 inches thick) then the coil should have been pressure washed. In order to do that they have to remove the coils and clean them.