I did an experiment with the central heater when I noticed it was blowing slightly cool air. I first let the temperature drop to 67 degrees. Then, I set the thermostat to 68, which triggered the heater to turn on. The air coming from the vents blew mostly cool with a hint of warmth. After letting the temperature level off at 68, I switched off the heater and let the temperature drop back down to 67. When I raised it to 70 degrees, the heater turned back on and the air blew much warmer and eventually leveled off at 70 degrees.
Is there something wrong with my heater? Why does the set point affect how warm the air that comes out of the heater is? Shouldn't the heater always blow with the same warmth regardless of the set point and just shut off when the set point is reached?