I’ve been using the heat for the past couple days being cold this year for the first time in my 2011 Chevy Impala LT (w/ heated seats), and there’s a couple weird things with it. First, it doesn’t seem to get as hot as I would have thought, or as my other past vehicles have. Second, the fan doesn’t seem to run the fastest on all of the settings. There is still a progression from low-high, so it’s not like its one speed only, but it seems to be just running slower on all settings. Lastly, when you switch from, for example, face vents to defrost, the blower motor shuts off, and then it takes forever for it to switch between those vent modes, and then the motor seems to turn back on. At first I thought it might be the heater core, but that wouldn’t explain the other stuff. Same for the blower motor resistor, but it doesn’t explain the less heat output. Would it possibly be the climate control module under the radio that is going bad?
Possible. Could be a failing blowing motor too. The reduced heat output could be caused by the fan speed, but also a failing coolant thermostat or air in the cooling system. Do you hear any gurgling noises? If it’s easy to inspect the blower cage, make sure there’s no leaves in that area preventing the cage from spinning freely. Does your car dash sport a coolant temp gauge? Anything unusual about how its been reading lately?
How is the cabin filter ? Has that ever been changed ? If not it could be completely clogged though that wouldnt account for the motor actually shutting off . If it hasnt been replaced then replace it , they normally should be replaced every 25000 miles . One of your blend doors could be getting flakey or interfering with the blower as it switches modes . It is never going to be cheap trying to have the dealer diagnose this as it could mean possible pulling part of the dash apart .