This is my problem: If I drive my NX for 15min or more, the air out of the dash is 5c above ambient temp in this cool fall weather. So if the outside air is 10C/50F, then the air coming with the dash is 15C/60F, this is with the HVAC controls displaying LO and using medium fan speed.

The REAL problem starts when I drive to a store and then start the car to come back home (within 20min or so) and the temp out of the dash vents is 25C/77F or greater. Outside temp is still 10C/50F when this happens. The hot air continues for 10 minutes or more, but eventually cools down to 18C/65F, or 8C above ambient.
I guess this is why my AC sucks in summer?!?

I've taken it to the dealer and they run the car for 5min and say there aren't any servo errors, so there's no problem. Frustrating.
Does anyone know how the heater system works? Is the heater core always receiving hot coolant or is it turned off with an electric valve?
Anyone have a diagram of the HVAC system?

Does anyone else experience this?
Using a hand held infrared thermometer to test the air temp out of the dash vents, how much higher is YOUR temp above ambient outside air?

 

Were your temperature measurements made in full automatic or manual mode?
Do NX models sold in BC have the optional electric heater ("quick heater")?

The cooling system diagram (attached) does not show a valve in the heater core loop.

 

Temp measurements were taken in manual mode with temp on "LO" fan speed showing 3 bars. There isn't an electric heating grid in the HVAC system for quick warm up as far as I know, you have to wait for the coolant to warm up to start heating the cabin. I looked at the option list for F-Sport 2, no mention of an aux heater.

Judging by the diagram, the heater core is always part of the cooling system loop and can never be turned off?

I'm assuming that means the HVAC system is controlled with baffles, and the heater core is supposed to be sealed off from airflow when heat is not commanded.
Mine must have a baffle door that isn't closing all the way (even thought the garage said there were no problems reported with the servo's) or there is a lot of heat transfer/heat sink when I shut the NX off, and restart it 20mins later.

The garage never took anything apart, maybe one of the servos is not attached properly and not closing the door all the way? Any idea of how to access them and have a look?

 

@n0v8orI didn't know there is such option electric heater. Can we buy that and add electric heater ourselves?

 

Endless:
All I know is what I found in the Toyota technical info (see attachment). The NX is sold in multiple markets worldwide. I would have expected Canada, in particular the northern regions, to be a target market for that option.

 

@n0v8or I would've imagine they will have it here in Canada too. I did a quick google search the part main sold in Europe sites.