Dual Zone A/C issues
 

Anyone out there had the following problem with their 991:

I have a 2014 C2S (May build) with 2300mi on the odo. Very few options, manual seats, and no memory seats or entry and drive. Just yesterday the A/C decided that it was going to blow warm air out of the passenger vents and passenger side top dash vent, but blew moderately cool air out of the driver side vents.

I tried cycling the A/C system, turning the car on/off several cycles, and running the dual zone sync/auto on and off for different intervals. Also tried Max A/C to no avail. The system seems locked into running the passenger temps at about 79F, and the driver side at roughly 72F. I even tried running the temps up and down from HI to LO and it is still stuck in some weird dual zone mode. Although interestingly enough, running the system to Hi, made the drivers side very warm, but the passenger side remained ~79F or so.

I've got a warranty service appointment for next Tuesday, but if you folks had seen this before and knew of a few other tricks to try to reset the system somehow I'd be interested in hearing them. It really seems like an electronic glitch where they probably need to reset or overwrite the HVAC software or something.

That's a bummer.

There are so many sensors in these systems I hope it logged in a error code in the computer so the techs can isolate the problems and repair.

Keep us posted on the repair route your dealer takes.

Are both temps set the same and synced?

Yes,

Both temps were synced when the problem occurred. I tried going full auto, synced, Max A/C, Passenger side set to LO, Driver side set to LO, upper Center console set to on/then to off, then I set the vents to Feet, Face, and then window. It was still getting the coldish air on the driver side and warm air on passenger side no matter what vent setting I ran.

I haven't tried to run defog/defrost, or change from F to C. I was tempted to reset the whole PCM system to factory defaults or pull the negative from the battery to see if that helped. However, I seem to recall the battery must be synced to the car or some other dealer required task, so I didn't try.

Since it is under warranty and so new I figured I'd let the dealer handle it.

I'd be interested to hear from the forum if they have any relatively benign tips to try in the meantime. Preferably something that doesn't require tearing the dash apart or tapping into the CAN Buss.

Probably a failed mixing flap on the HVAC.

I just had an A/C failure on my car, detailed in another thread. My fan quit blowing period no matter how I tried setting it. They first thought the blower motor was bad, then decided it was the "control unit" for the climate control, most likely part of the can bus system.
One thing you might try just for grins is the pull the fuses and reinsert them. There are two in the driver's side footwell access pertaining to the A/C. Probably won't help but it's something you can check yourself before the dealer visit.

You may also want to look into the likelihood that one or more of the "changeover" valves has stopped functioning. There are something like 8-9 or more of those little valve solenoids throughout the 991, and many members have at one time or another had the earlier rev. of the part fail. Dealers know this, but only replace the parts when they fail -- not before. I personally had 2 fail at different times - first for heat into the cabin with less than 2k miles, and the other at ~3-4k miles when the exhaust valve stopped closing.

Just sayin....... ;-)

2 of my change over valves failed as well - as above one for cabin heating and one for PSE. My concern is that these 2 are the 2 that we can easily observe. The other 6 are not so easy for us to know if they are functioning and I don't think waiting for fault codes is very reliable. There were certainly no fault codes when the above 2 valves failed.

And yes, they will not replace the other 6 even when 2 out of 8 has failed.

All good suggestions. Since the car is so new I'll probably just wait for the dealer to diagnose. I drove it in to work today and played around with the HVAC settings and it is definitely stuck in some weird mode. There is just some marginal amount of cooling coming out the driver vents and warmish air out of the passenger side. When I close off the driver side vents (with the plastic rotary knob on the vents), and open up the passenger side vents, I can direct some of the cooling air to the passenger side, but it is still not very cold.

I also noticed some whirring or hissing coming out of the dash area, like the internal vent flaps were trying to be moved around by a motor and may be stuck in some awkward position.

Hopefully they won't have to pull the dash apart and get into the bowels of the system. That would suck, usually once you pull a dash apart it never goes back into position correctly again and always has some squeaks and rattles afterwards.

Regarding the change over valves. It amazing in this day and age we are still having trouble with a basic component such as a solenoid controlled valve. This is probably 100 year old technology, and we still can't get it right.

At any rate, I still love the car and I'm in for the long haul, so I'm trying to live the "Sports Car Mantra"

Drive it...Enjoy it...and fix it when it breaks...

I had the exact same issue of warm air blowing from the passenger side vents. The dealer topped off the refrigerant twice and each time, the issue was resolved but came back after a couple of months. They finally changed an O ring somewhere and that fixed it for good.

I was baffled by the solution, but the air paths are apparently different for the driver and passenger side vents, making the passenger side more susceptible to low refrigerant issues.

Just got an update from the SA. He said the A/C receiver dryer had a leak and they ordered a replacement part and O-ring. They installed today and are going to check tomorrow to make sure there aren't anymore leaks. Sounds like the exact same problem MSIMHAMB had. I'll post replaced part numbers and details when I get the repair order.

I dropped the car off on Tuesday AM and it has taken them until Thursday to diagnose and order the part and install. Car is supposed to be ready on Friday. That seems like a long lead time for a repair, 4 days? I'm coming from BMW dealer experiences where it was 1-2 days max before the car was repaired for warranty or recall work.

Is this a typcial repair time? Not to mention it took 4 days to schedule an appointment when a loaner vehicle was available.

I was expecting faster turnaround time for repairs.

I am quite pleased (in a way) reading this; my car abandoned all interior heating this week, just blows cold. I was concerned it may be something major but I'm probably a victim of this selfsame issue.

Dealer fixing it on Monday.

That's pretty good in my book to diagnose and repair. Be glad that part was in the states. On the loaner front they could have just put you in a enterprise eco box but I bet they gave you a nice ride while your car was in the shop. Just be happy. :burnout:

So the car is all fixed now. The system was out of "FREON" as they found a leak in the receiver/dryer which was leaking "oil" onto the right front fender liner. They replaced reciever/dryer and two o-rings.

Part numbers:

944-573-143-01. Reciever dryer
999-707-556-41 o-ring
999-707-660-40 o-ring

Labor was charged at 1.42 hours

All covered under warranty but bill would've been $607.

Loaner was a 2014 base V-6 cayenne. Not bad, but my kids kept asking why they didn't give me a 911 turbo as a loaner. Kids...