A fan delay timer is a control feature that keeps the blower fan running for a short period after the heating or cooling cycle has finished. This ensures that all the residual conditioned air trapped in the Ducted system is pushed into the living space, maximizing energy efficiency. In the winter, it prevents the furnace from blowing cold air initially by waiting for the Heat Exchanger to warm up first. This functionality is standard on all ACIq and Mobile Home Furnaces to improve occupant comfort. If the timer fails, you might feel a sudden blast of cold air at the end of a cycle or lose out on the "free" heating/cooling left in the coils. You can find replacement timers and Control Boards in our parts department. This simple logic-based delay is a key contributor to the overall SEER2 and AFUE ratings of your equipment. It is an intelligent way to squeeze every bit of comfort out of every watt of electricity used.