I installed one of those heaters in my 54, and I am a little disappointed. The problem is that very little air is actually funneled into the defroster vent hoses when the doors on the heater are shut. While I don't drive my truck much when the temps are low enough for the defrost to be needed, if I did, I would be in trouble as I don't think I would have enough air flow through the defrost vents to keep the windshield clear, nor would it keep my feet from freezing if I elected to leave the vent windows open.
The other issue I have is the fan speed. The unit has two speeds, but both seem quite high, resulting in an awful lot of noise, without producing the necessary airflow.....
