Ok Thanks! In fact the first winter after our home was set up, we had the heating guy come out 3 times to replace a pressure switch that kept failing. We also found the infamous blinking 4-times light that meant the upper limit was reached. He found the problem - we got an upgraded furnace with the house, but they forgot to upgrade our ducts, so they were too small and heating up the furnace too much. He thought that was why the pressure switch kept failing. That was when he said I should open up all the vents to keep the furnace from overheating. Also, he lowered the size of the fuel orifice to lower the heat in the furnace. It worked, I didn't complain, even though I did pay for the larger furnace. Oh well. Thanks.