GM pm102 blower motor upgrade, moves more air, but rarely use high. In winter I cover the cowl vent intake and adjust the inner vent door so when I pull the vent knob out it opens the inner vent more early than normal, summer setting. The heater now draws air from inside and gets and keeps it warmer. I use my cj as a Dailey driver year round. Only gets truly nippy once it gets below 10.