Mine worked fine and kept the temperature constant, up hill and down dale unless I moved the "warmer" knob. Kept the cab toasty down to about 10 deg. F. Then cardboard had to be put in front of the radiator and a 195 thermostat but even that was marginal below zero. We're moving into that kind of weather now where I am. Seven degrees this morning. The later deluxe heaters had a door on the front that could be opened to recirculate the air in very cold weather. I passed one by in the junk yard years ago and have regretted that many times.

1951 3800 1-ton
"Earning its keep from the get-go"
In the DITY Gallery
1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.