JBPorscheOwner

Don,

In addition to my two questions from last night, I just thought of another important question that might make a material difference in the air flow to the driver's floor duct.

Since the Cayenne's 2-zone HVAC has separate fan speed and temperature controls for the driver and passenger, I would assume it has two separate blower motors. However, IF the Cayenne only has one blower motor, I would imagine that reducing the passenger side's fan speed would also allow more air from a single blower motor to blow through the driver's side vents.

Does the Cayenne's 2-zone HVAC have one or two blower motors?

Jack

deilenberger

Single blower motor. Velocity is controlled by flappers and basic blower speed.

JBPorscheOwner

Hello, Don! Thanks again for the information you previously provided.

This morning, while driving our 2011 Cayenne S with a 2-zone HVAC system over to another German-car-specific shop to help us determine why the air flow through the driver's side floor duct is poor when the air is specifically set to blow through the dash and floor vents, I noticed a different behavior I thought I would run by you.

The weather in Illinois has now changed so that heated vs. cold air is needed through the Cayenne's HVAC vents. Thus, this morning, I noticed that if the Cayenne's HVAC system is set to its default "Auto" position, a reasonable amount of air flows through the driver's side floor duct. However, if I manually set the HVAC system to blow through the dash and floor ducts, very little air flows through the driver's side floor vent.

Questions:
1. Any idea why more air would flow through the driver's side floor duct when the HVAC system is set to "Auto" vs. when it is set to specifically blow air only through the driver's side dash and floor duct vents?
2. When warm vs. cold air is needed through the vents to get to the desired temperature, is the Cayenne engineered to blow more air through the floor ducts when it is set to "Auto" vs. when cold air is needed? I understand most cars are engineered to blow more warm air to the floor because warm air rises and few people want hot air blown in their faces.

Jack

deilenberger

Jack,

Just thinking on it - I assume it got cooler in Illinois?

In manual mode (foot and face level vent buttons pressed), I would assume the air distribution flaps are set to equal size openings. That's just an assumption.. but - if you look at the size of the face level vents vs the openings in the panel under the dash (feel into them to get an idea of the size of these vent holes) - there is a big difference. Face level has two vents - with probably an area of around at least 6-8 square inches. The foot level vents are 4 or 5 holes about the size of my middle finger. One may be a tad bigger.. big difference in backpressure to the system, so the footwell isn't going to flow as much air as the face level vents if the controlling flap(s) are equally open.

When you're in auto mode - the system measures the duct temperatures and the cabin temperature. It determines how much heat and airflow are needed for the different areas of the vehicle. It turns the fan up and down, moves the air-mixing valves (hot/cold), controls the AC compressor, and the air velocity valves. Apparently with the ambient temps you're seeing and the temperature setting you've selected for auto mode - it has adjusted the flow ratios to the different outlets and allows more flow to the footwell.

It's also entirely possible that the heated air path is less restrictive than the cooled air path.

There is nothing I can say with any certainty. I don't have any magic insight into the engineers minds who designed the system... I just leave mine in AUTO mode about 99.9% of the time (I infrequently switch to defog to clear the windshield.) It works well for me in auto mode. Other people don't like auto mode (SWMBO for instance..) and feel better adjusting it themselves.

I'd be interested in hearing what the shop has to say after looking at the system.

JBPorscheOwner

Hello, Don! I finally have another update for you regarding the problem we are having with the 2011 Porsche Cayenne S we recently purchased, which only blows a trace amount of air to the driver's side floor vent when the HVAC controls are manually set to blow air through the dash and floor (not on the Auto position).

The local German vehicle specialty shop we took our 2011 Porsche Cayenne S to last week confirmed that, while the vehicle's computer "thought" all of the actuators were working correctly, the air flow to the driver's side floor vent was very poor when the HVAC controls were set to distribute air through the dash and floor. They then did a "deep dive" to visually inspect every HVAC actuator in the vehicle to see if the actuator flaps were physically moving to their correct positions. They also confirmed that all of the HVAC airflow ducts were properly attached and not loose, cracked, etc. Deep under the passenger-side dash, next to the blower motor, they discovered that one of the actuator's flaps were not engaging with their actuator motor. This reportedly resulted in that actuator's fins partially blocking airflow through that duct. They also found an HVAC error code - 008301.

After they re-engaged the detached actuator fins with the actuator motor and deleted the HVAC error code, they found that a little - but just a little - more airflow was being distributed to the driver's side floor vent when the driver's side air controls are set to blow air through the dash and floor vents.

Unfortunately, the airflow to the driver's side floor vent is still nowhere near where it needs to be (at least when the system is calling for cold, air-conditioned air). However, cold airflow to the passenger side floor vent is plentiful when the passenger side HVAC controls are set to distribute air through the dash and floor simultaneously.

Late this afternoon, just before the shop closed, I sat in the vehicle with their head mechanic and we tried adjusting the airflow and temperature settings on both the driver's and passenger sides of the vehicle. After about 10 minutes of misc. adjustments, the mechanic thought he heard the HVAC blower speed slow down when it should not. He's not sure, but he suspects the same HVAC error code may have tripped again. Tomorrow morning, h will see if the HVAC error code returns.

The mechanic also mentioned there are about seven vent holes in the floor ducting on the passenger side but only three on the driver's side. Thus, he said he is tempted - but not yet ready - to cut some additional vent holes in the driver's side floor ducting to increase air flow to the floor on that side. However, my wife, whose feet are much more sensitive to actual airflow - or not - than me, the mechanic, or just about anyone else - said that it feels like the Porsche's computer is simply turning off the vast majority of the airflow through the driver's side floor vents. Thus, she doesn't feel that cutting additional vent holes in the driver's side floor ducting will help. After the mechanic thought about it further, he said he too is unsure about whether or not cutting additional vent holes in the floor ducting will negatively impact the HVAC system's temperature and airflow sensors (i.e. trip one or more HVAC codes).

The mechanic also mentioned he wonders if integrating another HVAC booster fan into the driver's side floor duct to force more air through the driver's side floor vent at all times will resolve the poor airflow issue. I, on the other hand, wonder if the dash and floor actuator fins on the driver's side can simply be calibrated to intentionally blow more air through the driver's side floor duct without negatively impacting the HVAC system's sensors. However, when we tried to partially close the driver's side HVAC ducts in the dash, it did not materially boost airflow to the floor either.

Any additional ideas to mention to the mechanic?

Jack

deilenberger

Hi Jack,

Bunch of snipping of original content:
He'd not only have to cut holes in the duct, he'd have to cut matching holes in the panel below it. Not undoable - but probably not easy to do neatly so it looks factory.
I'd be curious where he'd fit in another fan.. the duct work doesn't look like there is enough space.

As far as calibrating the flaps differently - I see no easy way to do that. On at least iCarScan - there is no ability to put an offset into the control unit telling it to position the flap in a different position. If the mechanic has a tool capable (iCarScan can do it) - you can read out the percentage "open" of each flap - and that might be interesting to see - but I see no way to change that. They do what the HVAC control unit tells them to (or they're supposed to..) and I see no documentation on what readings to expect. The iCarScan does have a function where the user can tell each flap to open ##degrees - and then it reads out what it actually does. This test would be useful to see if all the flaps are doing what they're supposed to do.

One other thing to check - somewhere in the vehicle settings on the PCM (probably under the HVAC section) - you can turn off the upper dash vents so they don't automatically open when you close the center face vent. By default - closing the center face vent opens the upper vent and the effect on airflow would be none, or minimal.

Turning that off might help send more air to the footwell vent. Or not.

That's about it for me.. can't really think of much else that could be done. That's the problem with highly automated systems - they are not particularly good at being changed for your actual needs or wants. Back in the old day (old phart talking) - when heaters were heaters and the controls pushed cables that opened and closed doors.. this would have been a simple thing to do.

JBPorscheOwner

Thanks again, Don. I passed your suggestion to turn off the top-center dash ducts in the PCM and then manually close the dash vents about halfway closed to see if that boosts airflow to the driver's side floor duct when the HVAC is set to blow air through the driver's side dash and floor vents. The strange thing is that the airflow to the passenger side floor duct remains adequate in all cases.

deilenberger

I'd be interested in us getting into telephonic contact sometime when we both can be sitting in our vehicles.

I can get a LOT of airflow in the drivers side if I:

Select MONO so both sides do the same thing
Take it out of AUTO mode and put it in the footwell position
Run the temperature selection all the way down to "LOW"
Select "MAXAC"

That should bring the fan up on high speed. With these settings there is enough airflow in the footwell that I can easily feel it even with long pants on.

If you want to send me a PM - with a phone# - I'll swap numbers with you and we can try to setup a time to do this.

JBPorscheOwner

Don,

Thanks for the additional info. and, yes, I will send you a PM with my phone number. However, to reiterate, in our Cayenne, when we direct air to BOTH the dash AND floor, we only get a trace amount of cold airflow to the driver's side floor vent . If cold air is directed ONLY to the floor, we get plenty of airflow there.

I would be very interested to know if you still get a LOT of airflow to the driver's side floor vent if you set the airflow to blow out through the dash AND floor vents.

Jack

JBPorscheOwner

Don,

To update you, my local German car specialty service center confirmed my suspicion that, when the air controls on the driver's side are set to blow air through the dash and floor simultaneously the Porsche's ECU software is programmed to only allow the floor vent actuators to open the floor vents to 60% of their full-open position! Since the Cayenne has much fewer HVAC floor vents on the driver's side (see attached pictures) vs. passenger side, this combination results in very little air coming out of the driver's side floor vents when air is set to blow through the dash and floor. Since a TON of air comes out the driver's side floor vents when the driver's side blower controls are set to floor only, it is hard to imagine that Porsche would have intentionally restricted the floor vents to only open up to 60% of full open when the driver's side blower controls are set to blow air through the dash and floor vents (e.g. for fear of blowing up too much dust from the floor).

My German car specialty service center is trying to work with Porsche's Tech. Line to see if Porsche is willing to provide them with an ECU software update that fully opens up the floor vents when the HVAC is set to blow air through the dash and floor simultaneously. Porsche's initial response was that they had never heard that their ECU software is limiting the floor vent to 60% open when the blower controls are set to blow air through the dash AND floor vents simultaneously. My local German car specialty service adviser is a veteran who previously worked for a Porsche dealership and reportedly has an excellent relationship with a regional Porsche "after sale" manager. However, he is doubtful if and/or when Porsche may release a software update that fully opens up the floor vent actuators.

While waiting to see if Porsche can provide an ECU software update that fully opens the floor vents, I researched and found several other companies who appear as though they might have equipment that can reprogram the Cayenne's ECU and the HVAC actuators it controls. One of those companies told me they know Porsche released several software updates for the Cayenne's ECU. However, they doubted Porsche's ECU software updates would have significantly increased how far the Cayenne's HVAC floor vents open. Nevertheless, I asked my local German car specialty shop to confirm the software version that is currently running in the Cayenne's ECU is Porsche's current version.

In case Porsche does not provide an ECU software update to resolve this problem, do you know of specific brand, model and version that can definitively be used to reprogram that Cayenne's ECU to fully open the floor vent actuators when air is set to blow through the dash and floor simultaneously?

Jack

deilenberger

Hi Jack,

Interesting. Dunno of any specific tool that would have this capability. It sounds like Porsche is giving priority to the face level vents. The answer might be to restrict their outlets forcing air to take the path of lowest resistance (the foot vent.) You should be able to do that with the face-level vent controls on the vent.

For finding a tool - watch for one of our Russian members posting here and perhaps they could suggest something. It seems they get down into the code of many Porsche modules - which probably means they have a tool capable of doing this.

Don

JBPorscheOwner

To Anyone Who May Be Able To Assist with Resolving Porsche's HVAC ECU Programming Issue(s) That Are Causing Insufficient Airflow to the Driver's Side Floor Ducts:

Please see the attached summarized, one-page, PDF-based Porsche Cayenne Driver's Side HVAC Floor Duct Quality Testing Results document, which details the HVAC settings that cause Porsche's ECU to deliver poor air flow to the driver's and passenger side floor vents (particularly poor to the driver's side floor vents).

Major HVAC Driver’s Side Floor Vent Problem Findings:
1. When the HVAC’s MONO setting is ON, MORE airflow is incorrectly sent to the driver’s side floor vents vs. any other explicit setting that should otherwise maximize airflow to the driver’s side floor vents.
2. When the HVAC’s MONO setting is OFF, LESS airflow is incorrectly sent to the driver’s side floor vents when any of the following conditions exist:3. When the HVAC’s MONO and AUTO settings are OFF, the HVAC’s heated or cooled air should be directed to the driver’s and passenger’s explicit airflow location selections regardless if the HVAC is providing heated or cooled air!

sjg1138

deilenberger and
JBPorscheOwner:

Just want to thank you guys for a terrific thread. My car has been miserable to drive as it was impossible to turn off the heat. I removed the drivers side vent, plugged the holes with tape and the problem is gone! I decided to plug all of the holes just to make doubly sure. At some point I'll probably do the passenger side as well.

Anyway, thanks again!

JBPorscheOwner

April 2022 Update - Porsche HVAC Software/Firmware Flaw Does Not Allow More Cold Air Beyond Factory "Mono" Setting to Be Directed to 2011-2022 Cayenne Drivers Side Floor Vents!

To All Those Who Have Been Following and/or Are Interested in This Thread:
A local Porsche Dealer's Master Mechanic recently confirmed what I have been saying all along.
Porsche's HVAC software/firmware in 2011-2022 Porsche Cayennes (and possibly other Porsche vehicles) contains a flaw that does not allow more cold (air conditioned) air flow (CFMs) beyond the factory "Mono" (one HVAC zone) setting to be directed to the drivers side floor vents! ANY attempt to increase cold (air conditioned) air flow to the drivers side floor vents (by changing the output vent(s) and/or increasing the HVAC fan speed) results in LESS cold air flow to the drivers side floor vents than Porsche's factory "Mono" (one HVAC zone) setting!

However, when the vehicle is in HEAT mode, Porsche's HVAC firmware DOES allow more HEATED air beyond the factory "Mono" setting to be directed to the drivers side floor vents.
A local Porsche salesperson and I also sat in a brand-new 2022 Porsche Cayenne at a Porsche dealer ship and confirmed the above problem is also present in 2022 Porsche Cayennes (and possibly other Porsche models). Thus, at a minimum, this issue seems to affect 2011-2022 Porsche Cayennes - and likely Macans and other Porsche vehicles!

Last year (2021), at my request, my local Porsche dealership reported the above HVAC software/firmware problem to their Porsche factory contact. Despite the dealer's repeated follow up attempts, thus far, however, Porsche has reportedly not provided any response whatsoever.

If anyone can help resolve this HVAC software/firmware issue, please advise! Since this issue appears to be a HVAC software/firmware issue, correcting it should be relatively easy!

TyreReviews

Did you ever resolve this? Mine does exactly the same, except when I'm asking for cold air I get some random hot air in the passenger footwell too which is very annoying.