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2013 Nissan Altima heater fan issue

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.

" [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, . . . "

" I’ve had this in the garage at the dealership, [but that day was in the 50s outside ] and the problem didn’t occur. "

Of course you realize why they couldn’t find a problem.
Is this car still under warranty ?
Obviously, you’ll need to get to the warranty folks when the ambient temperature stays below 40*F. It would be best to leave it parked outside to cool down before a technician does his/her test drive prior to taking it inside.

Be sure that all complaints and observations (by you and service people) are noted on a Repair Order and be sure to get copies of everything.

Your description isn’t all that bewildering. This sounds like an issue with the blend doors or blend doors actuator, but we and you shouldn’t have to trifle over this if it’s covered by warranty. That’s what a warranty is for. You’ll just have to figure out a way to get it there when it’s malfunctioning or leave it with the dealer.

While you’re waiting:
Most HVAC systems have a diagnostic mode (at least my American cars - Chrysler and GM have it). Perhaps a search could give you information on how to make this Nissan enter this mode and self-diagnose its problem(s).

Is this vehicle under warranty ?

CSA

I have never had a problem with warranty repairs, and this should be one. You have to be able to replicate a problem before anyone can fix it. Figure that out and you should be good to go.

Next time it happens see if the recirculate is on or off. I bet what is happening is that it is recirculating air when cold, but switching to fresh air when warm. Most cars will do this because they feel it is safer to pull and fresh air all the time. You can override this by pushing the recirculate button.