Sounds like my 292, but in Southern Cal I seldom have to deal with ice. When I first bought the truck it had a 160 thermostat and on a cold rainy night I froze my butt and that's when I discovered it. I changed it to a 180 and it has trouble keeping any fog off, but does provide some warmth.
I have the stock four blade fan and no shroud and the gauge always sits at the top of the cold mark.
Just the nature of the beast. 180 is 180 so I think the heater design just isn't very efficient.
