I drive a 2020 Granite for plow trk for the state and the trk feels like i turned the heat back about 1/3 of the way but only after I drive the trk for a few minutes. When idling, it will cook as supposed to and if empty and on flatland ot stays hotter as well but as soon as I load up and start climbing hills, the defrosters get cooler. If split between feet and defroster, you can actually feel the feet is still hotter than the defroster. Its been to Mack and spent over $5k and still mot fixed after 1 year and of course our mechs just say nothing is wrong with it. I'm about to tell mngmt I want a different trk but I've taken care of this trk for 5 yrs and would like to keep running it. Any ideas cux Mack has done most everything i can think of. Thermostats, heater core, water pump, control module, and found a broken wire at 1 time but still not hot.
