The temperature this morning was -5F (after a -20F night), and my HVAC heating decided that it would take a vacation today.
It was blowing cold air at all temp settings (I tried 62F to 90F), and fan speeds were all over the place at AUTO. The various fan speeds worked if selected manually, but still blowing cold. The selector between the dash fans is set to the 3 red dots. Coolant heat was right at 12 o'clock 2 mi into my 12 mi commute.
FSR and heater valve ? The thermostat is 2 years old and has about 40k on it.