I have a Whirlpool (Heil / Quaker) "high efficiency" gas furnace rated at 100K BTU/HR. The model is NUGK100AH01. It's the kind that exhausts out the side of the house through a 1-1/2" or 2" PVC-40 pipe. It keeps the house warm just fine, even on very cold days. This time of year I always see steam coming out of the exhaust. It also constantly discharges water into a floor drain. Lately I've noticed that the thing inside the front of the furnace that looks like a turbo-charger is cycling on and off - even when the blower runs continually. Does this neccesarily indicate a need for service? Burners are good and blue and there's never any ignition problem.