I have a Ruud furnace - model UGDG-12EARJR. Full heating cycle is too short. The furnace goes on, but it shuts off before it reaches temperature set by thermostat. After about one minute it comes back on and stays on until it reaches the temperature set by the thermostat.

Does the fan continue to run?


Are you observing the burners turning on, the fan starting and continuing to run, the burners shutting off for a period, lighting again while the fan remains on, and continuing to cycle like that?