Heating is blowing cool air inside our home through the air vents. Checked tstat, brakers, and propane levels... all seem to work. What could be wrong?

Is the unit firing? If so, you may have a problem with low LP input pressure due to a faulty regulator. If so, the unit will not deliver heat at its rated capacity.

Thanks for the reply. I just know that the combined unit is still blowing/running even though the tstat is off.