WHile visiting my parents in COlorado, I noticed that when the thermostat clicks for the second stage, that stage comes on, but only for about 5 minutes, but the thermostat was not satisfied, and still calling for the second stage of heat. I investigated further and noted that when the second stage goes off, the burner completely shuts off for about 30 seconds, then re-fires for the first stage only, then after a while the second stage will kick in again for about five minutes, and so on. The second stage is never on long enough to warm the house, and it takes forever to warm-up the house. In the viewport in the fan compartment, the L.E.D. blinks three short blinks, which the blower door panel says is a pressure switch problem. Both pressure switches seem to be working fine by checking with the cheapo voltmeter my dad has when the burner fan switches to the higher speed for the second stage, and the tubing to the pressure switches are in good condition, and not cracked or yellowed. I will be calling a Technician on Monday, but am curious as to the problem. 2 questions, is this dangerous, and what might be the problem? They are on a fixed income, but I have convinced them it should be repaired.