:confused: hello, I recently bought a used bryant ceiling mount furnace model#125-341,not sure of man. Date but guessing older vintage. I went through completely and cleaned thoroughly,mounted and fired it up. Pilot stays lit fine,fan kicks on right away?before the burners ignite. Am getting nice blue flame down entire length of all six burners-however flame appears to be to small approx 5 inches tall. I do not see an adjustment on regulator.there is a pilot adj. on a separate regulator(w/primer hold down button)fan runs entire time basically blowing cold air-warmer towards bottom. This is a 100,000 BTU furnace and should be blowing hot air and shutting off fairly quickly in my shop. It eventually warmed up the shop and I turned the thermostat down, burners went out and fan even shut off-so I'm not sure about fan, but for sure flame not right.this was originally a narural gas unit, but converted to lp and used in that mode prior to my purchase.

A five inch flame above the burner is actually large for a 100,000 furnace but if they are blue and not lifting off the burner that should be fine.
Now about the blower. To me it sounds like your heater is wired without a fan switch and therefore the blower comes on as soon as you turn on the thermostat and it will cease to run as soon as the thermostat is satisfied. When wired this way it takes longer to heat up an area because it is blowing cold air for the first few minutes. I am sure you could add a fan switch if you wanted to.