are all those temp sensors inside the ducts the same? - can/do they fail often? - i might try swapping the center vent and footwell sensors to see if there's any difference - i can't see from the diagram above a combo of doors that would fail and just send heat to the left footwell - but since there are temp sensors i assume there is a way for each outlet to be controlled individually - make sense?

 

I've not seen the inside of the plenum, so I can only speculate. It "looks like" the temp servo for each side controls temp to ALL vents on that side. If the temp servo 'failed' then you'd get heat out ALL of the vents on that side, not just the footwell. I can't see how it would be able to dump heat to ONLY the footwell duct, while still sending cold air out the rest on that side.

Question, do you use the Auto mode for ventilation or make manual selections using the center console buttons? If using Auto I'd wonder if there's some sort of open/closing 'glitch' changing often enough between heat/cold while having only the lowest servo open for flow to the footwell? Given how quiet these are the only way tell would be checking airflow, perhaps by using a small anemometer (which would be tedious, no doubt).

 

not in auto mode - i just set temp to low and adjust the fan as needed - what are the temp sensors in every vent for if the temp to each one cannot be regulated separately

 

Because you might not be directing air out all of them? Only some of them? That and I don't think there's temp sensors in "every vent" but it's not a hill I'd die on trying to prove.

Look at the servos listed. There's not a separate temp servo for every vent, there's one temp servo for left and one right. And then there's one servo for every output vent. Seems reasonable to think there's not way to get heat out of one vent while getting cold out of another on the same side. I could be wrong, and would welcome someone clarifying it.

 

ok..so i have totally mis-stated what is going on in my car - it's 73 degrees here in denver...windows down weather - went for a 25 mile drive with none of the buttons on the center console activated - really didn't feel any heat at all coming out of lower vent - parked car for 5 minutes and drove back home - then i did feel heat at that panel and lower vents - opened the center vents and felt heat there also - when i got home i sat in passenger seat and did indeed feel heat on that side also - i guess i'm usually in car by myself and can't feel passenger side vents - and usually i only have those center vents open so they get mixed with outside air more and don't feel as warm as the "closed" lower vents - so it appears it's leaking warm air all/most of the time - does turning the car off open that heater mix flap (no vacuum) so when i start it again it might not close all the way? - i guess one of these days (i know i've said that before ..but been busy) i will actually have to take it apart and see what the issue is - this is almost the time of year when this becomes a real PITA - don't ned A/C or heat...but i am getting heat anyway

added : are all these flaps electrically controlled? - if so no vacuum when car is off would not be the issue

 

PIWIS has menu items (the dealer programming tool) to recalibrate the HVAC servos. I'd imagine an independent shop that had a PIWIS setup would be able to program a 2012 by now.

I'd wonder, however, if there's something that might have fallen down in there that could be blocking the flap from closing? I have no idea how clear a path there is from the various ducts back to the central core. I've had reasonable success using an inexpensive WiFi inspection camera to help get a better look into various parts of my boat and ceiling/crawl spaces at the house. The idea is you pair you phone to it and use the phone's screen to see, so you've not flapping the screen around while snaking the camera cable around.

This one works ok for me:
I'd try to get a look-see down in there first before calibrating. Because it'd do no good to have the servos readjust themselves if the duct opening it blocked from closing fully.

 

Yes, they're electric, not vacuum pressure.

This is a diagram showing a bit more of the ducts coming off the main unit:

I have no idea how much space is in there when the ducts open/close. Nor whether they're fragile. I do know the temp sensors (the blue items 1,2 & 3) are something you want to be careful about.

I gather the duct openings on the side facing us in that picture are for the center vents alongside the PCM screen. The one across the side facing away are for the defroster. I assume this because that's where the servo motor #'s match up to their function. The same ducts that handles the left/right front footwells also has a port for the duct to the rear footwells. Though if you have 4-zone AC the rear areas (and powered seat vents) are ducted from the rear unit.

From what I gather the blower motor cage is not located under the servo/flap assembly, so you're not likely to have anything get broken by it. It's way over on the right side.

I'd use the inspection camera to carefully go in from the center vents alongside the PCM. Do it while on heat mode with the blower on high, and manually with the vent selected (not auto). The idea is don't choose a temp or setting that'd have the system start moving any of the servos and duct flaps around. Likewise with it on as cold as you can set it (max ac).

 

for the record, I have played with my AUTEL MS908S diag tool. I have activated all servos many times and making sure they report 100% position and 0% position. The issue seem to be gone now. I will validate more in the next following week....

Mart

 

One thing I've noticed on mine is occasionally the computer seems to get confused. If it's night time, for example, and I have the temp set to 68, it'll start pumping heat, even when it's still hot in the car and outside.

I tried bumping the temp down a couple of degrees to get the temp sensors re-engaged or recalibrated or whatever and then it seems to work right again when I reset it to the desired temp. Air goes where it's supposed to all the time, it's just the temp sensors seem to get confused.

If you haven't tried changing temps (and leave it at the new temp for a good 20-30 mins), maybe that'll help.

 

looked at this again today - tried to take everything under there out so i could at least see the servo motors and flaps - was unsuccessful at that - i think you'd have to disassemble almost the entire dash - the servos are tucked behind what i believe is the BCM - i went as far as removing all the trim on the drivers side and the airbag underneath but i think you'd have to have the PCM out as well - i just wound up putting it back together - wasn't prepared for an all day job - wkearney99...i pulled the vent on left side of PCM and there is a grill behind there with about 1/4 inch square openings..so i don't think anything could fall down and obstruct the flaps...but?

 

Yeah, I got the impression that doing anything with that airbox assembly would be a HUGE labor time-sink. That's why I figured a cheap inspection camera might be a viable option. I'll get mine off the boat this weekend and bring it home to take a look.

 

not sure you could even fit the camera tube through those openings in the grill behind the vent - i'm thinking it's either a visit to porsche or buying a coding device to operate the flaps and see where the problem lies - i really don't want to do either one - and in a month or so it won't matter as i'll be using the heat anyway