Windshield condensation. UPDATE.

Okay.... The 996 has had this problem since 99. Porsche has been made very well aware of the problem and its potential hazards. I have a letter hanging nearby wherein they simply refused to even think about a corrective measure. THe good news is that you can probably take your Cayenne over to VW and maybe talk them into doing their Touareg firmware fix for this exact same problem. The problem occurs in my 01 C4 only after the cabin has been cooled to very near the setpoint, 72F in my case. Once that happens a significant portion of the COLD airflow is automatically routed out the defrost/defog/demist ducts (only GOD know why??) and soon after the windshield surface temperature will begin to decline toward the outside atmosphere's dewpoint. The higher the humidity the quicker your windshield will begin to fog over. I first reported that to Porsche in late May as I returned my 01 to the factory to be shipped to the US. On our subsequent drive from the east coast to Seattle we encountered an early evening rainstorm after a HOT day in August near Birmingham AL. Shortly after driving out of the storm I discovered that I needed to use the wipers to keep the condensation cleared from the windshield. If you check the 996 thread I think I posted this info there years ago now. I avoid the problem by manually selecting dash outlets only or dash and footwell if I don't have recirc on, which I mostly do during the summer months but NEVER during winter. I recently checked with the service manager at Barrier here in Bellevue and we verified that the 04 996 series has the same flaw.

I have the same problem on my 04 c4s

My 2002 C2 cab has same problem.

I have the same problem on hot high humidity days like yesterday in NY. It.s manageable though, I've had other cars that do the same thing but only when it VERY humid outside.

Went to Hilton Head last summer. Stopped for gas early evening after the long drive. The whole dang windshield misted up as I got back on the highway!! Had to quickly figure out what those little symbols on the AC controls meant in order to redirect air flow. Even then, some air still managed to get to the defroster.

Same problem. I never realized it was a factory issue, I just always assumed that it was my fault for keeping the interior at 66 degree in 100 degree weather.

The funny thing is that if you actually select defrost/defog/demist mode, you get HOT airflow to the interior surface of the windshield on the hottest day of summer. Just as it should be IMMHO.

It hapens in every car I've had (other brands). Turn the AC on, increase the fan speed and it's gone.

I have the same problem. Is it fixable?

No the AC is what causes the problem. It cools the windshield to such a temperature that the condensation takes place on the outside of the car. Increased fan speed only causes the area effected to get bigger. I wondered what the hell I was doing wrong because I have have this problem also (funny thing is I don't remember having this problem with a former Boxster). Since the climate I live in is very humid and hot in the summer it happens every time I use the AUTO climate control in the summer. The condensation will start to appear within 5 minutes or so. I have given up using the auto feature with the AC and select the dash vents and adjust the fan manually. Has anyone attempted to get the firmware update from VW? I had a 2004 A4 rental that had this very same problem.

Happens here too. I just use the middle vents button for a few minutes and it goes away. Worse, if I have the top down, and it's really hot out, I'll run the A/C only to get water all over the center console (vent surround on dash). Really stinks how that happens. Did not happen on my '99 that way, but does on the '04.

I tried ReJex on the window to see if this would help, it did not

I have a solution....when the condensation gets too bad...GIVE IT A SWIPE WITH THE WIPER! Sheesh

I have the same problem with my '04 C4S Cab. And no, it did not happen in my SL500 or 745Li, so I don'y believe this is an insurmountable fact of automotive life in humid climates. The other manufacturers probably increase the flow of non-cooled air to the windshield when necessary.

Mmmm, I have another problem. I have this rumbling sound that seems to be coming out from these 2 obround tubes that come out from underneath either side of the rear of the car. It only makes the sound when I start the car. Does anyone else have that problem? Guys give me an effing break. It happens to everycar out there! Can't see how Porsche can be responsible. That is what the defrost is for. And yes I had the same problem, when you do turn on the defrost it blows hot air, BUT leave it running!. I found, on my car at least that it only blows the hot air for the first few seconds, if you let it run, the hot air turns to cool air. You need the hot air to get rid of the condensation.

I disagree that EVERY CAR out there has this problem. Under the exact same climate conditions my wife's BMW 328i does not have any of these problems. Hit the auto button on the climate control and forget (well accept for the stupid design by BMW that you have to hit the snow flake button if you want the AC to work). NEVER any condensation. Co-workers CLK500..No problems. My parents Honda Accord and Toyota Camry...No problems. There is a design flaw somewhere in the climate control system of our cars. Is it a big deal? No it annoying. Is there a work around? Yes (choose the vents and forget the Auto feature). Does it bother me that much? No. If there was a fix, would I get it done? Yes.

Maybe this will help clear up some of the apparent confusion.... Windshield Condensation 2001 Porsche 911/996 C4 In May of 2001 I took factory delivery of a new 2001 Porsche C4, a stunningly beautiful car and an engineering masterpiece if ever there was one. During our subsequent 10 day tour of the castles of Europe, most days being quite warm and sunny, I did note that the A/C has some sort of unique peculiarity. It seemed that I had to continually change the temperature setpoint in order to maintain a satisfactory comfort level within the cabin. I reported this to Porsche when we returned the car to the factory for subsequent shipment to the US. Admittedly I could not be very definitive at that time about the detains of our A/C problem. In late June of that year we picked the car up at POE on the east coast to drive it home to Seattle. We departed Charleston just after noon on a very hot day and as evening approached we were in Alabama nearing Birmingham when we encountered a series of heavy rain showers. It had been as exceedingly hot day so the highway dried quickly making the rain showers basically a non-event. NOT! It was not quite fully dark but in the late evening when I started to notice the oncoming headlights had taken on a weird appearance. It wasn't long after that that I realized that the exterior surface of the windshield was entirely covered over with a thin layer of condensation. I immediately turned on the wipers and cleared my forward vision. Because I had encountered problems of this nature on a brand new 1992 Lexus LS400, condensation on the INSIDE of the windshield, during the winter of 92-93, I was immediately suspicious of just what could have caused such an occurrence. So one of the things I did immediately was check for warming airflow from the defrost/defog/demist windshield outlet ducts. What I discovered was VERY COLD airflow, LOTS of it!! WHAT??!! Must be something wrong with my climate control system... NOT! The next day I contacted my salesman and asked about this occurrence and he said that it was new to him. As it happened we had not yet sold our 99 911/996 so when I got home the first thing I checked was if the A/C would intentionally CHILL the windshield. It did. I recently checked a new 2005 911/996 model at the local dealer and it does the same. What was happening during our tour in Europe was that once the cabin temperature reached or neared the temperature setpoint the system would automatically route a substantial level of the cooled airflow to the windshield which, instead of contributing toward the cooling of the cabin and its occupants, was being used instead to chill the windshield surface and thereby the huge heat sink otherwise called the earth's atmosphere. So to compensate I would lower the setpoint, the defrost/defog/demist ducts would close accordingly and shortly thereafter we would find ourselves uncomfortably COOL. So, RAISE the setpoint.... And so on and so on...... Shortly after we returned to Seattle, eastside, Redmond and Woodinville to be exact, Barrier motors used their diagnostic analyzer to verify that the system was operating as designed. What I distinctly remember was that I took it in for service about this problem and as it was being written up and we got to the details of the service requirement the manager said that the windshield cooling operation was normal and discarded the service write-up. I don't now remember if it was on that occasion that the diagnostic device was used or if it was a later occasion. Apparently in March of 2002 the district representative contacted me to inform me that this, cold airflow to the windshield, was normal operation. What I have done to combat the problem is that I always select max cool and then manually adjust the blower speed to achieve and maintain myself and my wife at a comfortable "cool" level. The system then NEVER approaches or reaches the setpoint so it does not automatically switch to routing airflow from the defrost/defog/demist airflow ducts. If I am not mistaken the above procedure will also yield returns in better fuel economy due to less frequent operation of the A/C compressor. So why is this issue so all fired important? Because it is a quite serious SAFETY issue and it is quite possible not just a few people have already been injured or maybe even died from accidents directly attributable to this design flaw. The Lexus design flaw was and is the responsibility of NipponDenso, Denso USA, the primary supplier of automatic climate control designs and control components to most Asian automotive manufacturers. Assuming Bosch is the supplier of the Porsche system, most automobiles of European design are likely subject to this same design flaw we find in Porsche 996's. An example of why this design flaw should be considered a serious safety defect is indicated by the following incident. Some years ago I drove a relatively new Chrysler Town & Country minivan from Seattle to Cannon Beach OR. It was a relatively hot and sunny summer day and I have no doubt that as we approached the area of the Oregon coast in the late afternoon the relative humidity outside rose substantially. The final leg of the journey followed the coast line fairly closely with lots of curves and some fairly steep inclines and slopes. As we were descending into one of these "valleys" the windshield became opaque fairly quickly. We were traveling fairly slowly at this point so it was not terribly threatening, I remember simply turning on the wipers and not thinking much more about it at the time. While in this case the windshield had not been directly cooled as it is in the Porsche, I had been running the A/C "full-on" due to the high occupancy (4 adults and 3 grandkids) and bright sunlight streaming through the windows so the windshield, by default, was obviously chilled to the fairly high dewpoint of the atmosphere "lying" in that valley so near the ocean. Just this past weekend I discovered that the VW Touareg (VW's version of the Cayenne) is subject to this same design flaw. But unlike Porsche, VW has stepped up to the plate and is already supplying a firmware fix, reprogramming, the climate control ECU.

I have never had the problem that you guys are speaking about. You WILL, however get condensation on the inside of the windshield is you turn off the air compressor after running it for a while and the dew point is high outside. This occurs in all my car and trucks. I run air all day long in summer and winter and have never had condensation when the air is running. Inside or out.

Yeah, well, YOU are in CHICAGO! The sun rarely shines there, we all know that. Just kidding. But here in the south, with heat and high humidity, we face this all too often.

Wwest, Seriously, are you a lawyer by any chance?

No.... Retired self taught electronics engineer. home page is: strobedata.com

I agree this is a concern, turning on the windshield wipers solves the problem, but only for a few seconds and then the condensation on the OUTSIDE of the windshield recurs, the wipers also can scratch the glass if they are on and the rest of the glass is dry. for those of us with rain sensing wipers, it means turning on the wipers in the non intermittent mode or repetatively pulling the wiper stalk (to wash the window) or turning the wipers on and off, not the type of activity that is a bunch of fun when you are trying to enjoy the car. This is a safety issue and can be solved by Porsche reprogramming the a/c so less cold air is sent to the windshield

I have the rain sensing wipers - it's not a problem. Here's what you do... Move the level to position zero (wipers not on). Now, when you want a swipe, move the lever up just a little - not enough to move it to position 1. The wipers wipe and the lever returns to position zero. Easy, fast, effective. Really though, I think either you people are being a little too **** or I am a little too easy going. Next you will be complaining that the suspension gives a rough ride. It's a fantastic car - one that many, many people the world over would give their right arm to own. So stop trying to find faults with it and just enjoy it. Barry

I have also noticed this problem -- We also have a Lexus that does this. It becomes a greater problem as the glass gets pitted by stones and sand -- the windshield wipers are less able to take care of the problem. On the Lexus I make sure that I have very good wipers - I have tried coating the windshield with little results. All cars will do this in certain conditions -- but the Porsche and Lexus systems send too much cold air to the windshield as the car reaches the inside set temp. It is a real pain at night when light hits the windshield. My Jaguar had the control box changed when it was new -- In that system "OFF" was very low fan and defrost. In the winter starting the car would instantly fog the window inside. The new off was very low fan and floor. With the curve of the glass in the 911 the cold air out of the defrost vents is able to cool the whole glass area.

Lexus........Hmmmmm. The only design flaw I know of with the Lexus climate control system gives it a propensity to fog over the interior of the windshield. You may be having the same problem I described in the T&C. The Lexus provides ABSOLUTELY NO (**) airflow toward the windshield in cooling mode (air outflow primarily from the dash outlets). After a long period of cooling the cabin the windshield will be cooled somewhat inadvertantly. ** If there is airflow to the Lexus windshield in cooling mode then Lexus service should repair your system. There is a warning in the owners manual CAUTIONING owners to NEVER use the defrost/defog/demist mode during humid weather as that will definitely CHILL the windshield to the outside atmospheric dewpoint. Once the Lexus cabin has acclimated to or near the temperature setpoint it will NOT provide heated nor even warmed airflow to the windshield in defrost/defog/demist mode. Once your comfort setting is reached the Lexus system (designed/manufactured by NipponDenso, Denso USA) will automatically switch to cooling mode (on the COLDEST day in the dead of winter). Thereafter it uses the dehumidification capability of the A/C, EXCLUSIVELY, for clearing and/or preventing interior windshield condensation. I have found the defrost/defog/demist mode airflow to the windshield to be as much as 20F cooler than the airflow used in normal cooling mode just previously. And remember that the dehumidifcation capability of the A/C declines precipetously with OAT below ~50F until it is practically non-existent below 40F and absolutely non-existent below 33F where the factory designs disabled the A/C compressor.

A litlle fog-x on the outside of the windshield should fix the problem. Scroll down till the third item. http://rainx.com/frame_auto_new.htm

If you increase you vehicle speed to grater than 130 MPH, you should not have any problem. Just tell the cop that you needed to go that fast to assure you had good visability.

Jumpin' Jiminy! A Data General Nova emulator with a data channel I/O interface to boot! There's a market for such a dinosaur?? ... think I have an async data channel card up in my attic somewhere if you want it wwest.

We have already developed a "virtual" driver for a USB 32 port multiplexor with RS232, RS422 and 20MA capability. But RDOS & AOS ( RSX, RSTS, and RTE) still "thinks" its talking to the native I/O device, your board in DG's case.

Correction... Inadvertantly discovered that a max cool setting does not allow defrost/defog/demist to operate properly, gets only COLD airflow. But a setting of 1 degree above max cool, 64F in my case(01 C4), seems to work fine, HOT airflow to the windshield in defrost/defog/demist mode. And 64F is probably still low enough that it's never reached and so there would likely be little danger of the system automatically switching to partial windshield cooling and the resultant potential for windshield condensation.