My 2013 Altima has a peculiar problem. When the outdoor temperature is below 40F, the heater system works fine when the car starts out cold, but within 20 minutes the air circulation begins to fade, it’s as if the fan goes slower as the inside of the car warms up. Note that this is not an automatic heat/air system. It is manual controlled. When the car starts, there is plenty of air moving, even with the fan set at the lowest position. But when the car is warmed up, there is weak circulation even when the fan is turned up to the highest setting. If the car is shut off for as little as 10 or 15 minutes, the air circulation is fine again until the car warms up. Even more bewildering is that when the fan is turned all the way up, it can be heard quite distinctly, although the air isn’t moving very well. It’s as if something is blocking the flow of air.
I’ve had this in the garage at the dealership, but that day was in the 50s outside and the problem didn’t occur.
I’m wondering if anyone has heard of this problem, or experienced it.