I have a Armstrong gas forced air furnace and a Armstrong AC unit, not sure of the model numbers. Anyway, the fan short cycles when the AC is on. I tried it with the heat and it runs fine. It will bring the temperature down in the house it just takes longer to do so. I am hoping this is just a thermostat problem, I just replaced the filter also. the short cycling differs, sometimes it runs for 30 seconds and then shuts down for 15 seconds and repeats,other times it will run for maybe 3 - 4 minutes and then shuts down for 15 seconds and repeats. Any help would be GREATLY appreciated!
Need to post the model #s of both the furnace and the outside ac unit, and the tonnage of the outdoor unit if you have it. How many square feet is your house, and at what temp are you trying to set the thermostat at.