Well, it's not "normal" but it is a commonly reported problem with the auto-climate system. I have experienced it many times, usually when the outside temperature is around 60-75F. You will find dozens of threads about this issue dating back to the original 2003 model, and many people speculated that it was caused by heated source air from the engine compartment. However, I remain convinced that it is the result of a control software bug in the auto-climate system. The air control doors are being commanded to open at times when they should be closed. According to the FSM, when you select the minimum system setpoint of 60F, the control doors are supposed to positively control. Quite simply, they don't always do that. Software on cars is complicated, but shame on Infiniti for not fixing this bug for 4 years!

 

i noticed that too but i use manual climate (regulate the temp myself). since it was winter here i had the temp up to 32c and when the unit was off while driving hot air would blow out the vents.

so i turned the unit on, reduced temp to lowest 18C and turned off unit. bam! no more hot air.

 

I don't use the auto and have not had that problem. Try it without and see what happens.

 

the vent pulls air from the window cowl, so it's sucking in air from the hot engine area, that's why it's hot. it's normal to be alittle warmer.

 

Well, that would seem to be a logical thought. Yes, the air intake comes from the cowl at the windshield base, through the battery compartment area and the driver's side compartment on the other side. So of course you would expect the temperature there to be slightly warmer than ambient.

BUT the "hot" air that the climate control system occasionally (inconsistently) puts outs is MUCH warmer than ambient. And the fact is that the air control doors (there are two of these in the Premium equipped cars - for driver and psngr) are being commanded to open during the time the hot air is observed. I have even had times when the passenger-side ducts were putting out ambient temp air (say 65F), and the driver's side was putting out 90F air! Since the source air for both sides is the same, the only explanation is that the air control door on one side was open - even though I had set the auto-temp at 60F (min setting). If you play around with the system (flip A/C on/off/on, etc), or wait a few minutes, the system is known to correct itself. But then, it can also go back to blowing HOT air!

All of these symptoms, especially the inconsistency, and observed difference between L & R side temps, point conclusively to a logic/control error in the auto-climate software. My speculation is that Infiniti is well aware of the issue, but for business-case reasons has decided not to implement a fix. Presumably it's all about cost. If the software cannot be easily re-flashed (and I have not heard of this capability), then the cost of hardware change-out would be very expensive. So instead, they simply advise people to turn on the A/C - which seems to override the software logic bug and return the system to proper control status. Until you turn the A/C off....

 

Next time that your A/C is off and you feel hot air coming in press the temperature down button a few times, then turn the A/C on and you will see that the temperature has decreased. Bring it down to 60 and turn it off, you should be good that way; at least that is what I do and it works for me on my 03 G.

 

https://g35driver.com/forums/faq-diy/7546-heated-fresh-air-cure.html

Have to get Msedanman to update the pics...help us Colin

 

That post asserts that the hot-air problem can be fixed by plugging some holes in the intake cowling. I have no doubt that this might help a little bit, but it's not going to solve the control logic software bug which is the real problem. Cars have been setup to intake air from the engine compartment for many years now - ever since aerodynamic design practice took away the old grille work approach.

 

Noremac----you got it 1000% right on the control/logic part, but if you look at the diagrams in the shop manual, the problem is with the air control doors as opposed to what you were calling "heater control valves." In the old days a heater control valve shut off the flow of engine coolant to the heater core when not needed, but the early G (specifically '03, which is what I have, not sure about later model years) does not shut off engine coolant, it just regulates how opened or closed the air flow doors are. The heater core always receives coolant flow.

(If by heater control valves you meant to say the air doors, then I apologize for nit-picking! )

I always thought this malady could be easily observed and diagnosed if one had a flexible "borescope" type of observation tool that could be fed into the duct work far enough to see what was happening with the air doors in the climate system plenum. Like this inexpensive model: http://www.fiberscope.net/servlet/th...cope%2C/Detail


I have been putting up with this annoyance for 4-1/2 years, but just a few weeks ago I was at the plumbing dept at Lowe's and saw a water valve that I think I will try this summer when I flush my cooling system. It's a top-lever brass shutoff valve with pipe nipples on both ends that sure look like they are the right size to fit on the hoses that lead to/from the heater core. Splicing two into the heater core loop (one upstream and one downstream---might not need the downstream) should shut off the flow of engine coolant.

I think this will be safe to do since the shop manual clearly shows the cooling system flow circuits, and the heater core loop is an independent loop, the restriction of which should not affect anything else.

 

Couldn't you just use "recycle" mode than "fresh air" mode to stop the air from coming in? This works for me. I had a same issue with '97 Maxima. Maybe it's a "Nissan" thing.

 

Yep! That's exactly the terminology I should have used. I didn't have the FSM in front of me, but you jogged my memory! I've edited my posts above to reflect this...

If you do that, then the auto control system won't be able to mix in any warm air to help regulate cabin temp in the A/C season. It will still be able to use fan speed and compressor ON/OFF, of course. Maybe that's enough control, but you could experience lots of compressor cycling. Or you could run in manual mode! Interesting idea...