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My 06 AC is getting wimpy and may need a recharge (at least that's what I hope).
Is this a DIY, or independent shop fix or is it another typical Porsche-only service that requires a dealer to do?
I know some of these modern systems are so convoluted that it requires specialized equipment by trained technicians. It wouldn't surprise me that this is one of them.
It isn't like the old days of R12 systems where you added freon until the suction hose on the compressor started frosting up.
Since your system is still functioning to some extent - you apparently haven't lost all your R134 and gone to air. That's a good thing.
At a minimum you need a set of R134 gauges (Harbor Freight has some I think) so you can read high and low side pressure. A sling-thermometer (web-bulb, compensates for humidiy) is also useful to get accurate readings of the output temperature of the system vs input. It would also be useful to have a diagnostics tool capable of reading the temperature of the evaporator, and the internal system pressures. Then you need a service manual to use to check all the values against.
So - long story short - you're probably better off taking it to a pro.
DO make sure your cabin filter is clean, restricted airflow can cause reduced cooling capacity. If you take it to an independent shop - search for one that specializes in air-conditioning. Back in the old days (like 1970's) there used to be lots of radiator shops that morphed into radiator-air-conditioning shops and they were usually pretty competent.
You don't want to overfill the system (from empty they are filled by the weight of the R134) - since this can cause damage to stuff like the compressor - trying to compress more gas than belongs there.
BTW - legally - a shop can't add refrigerant to a system unless they find and fix the reason for loosing refrigerant. How strictly that law is followed is questionable.
So - long story short - you're probably better off taking it to a pro.
Likely.
Originally Posted by deilenberger
BTW - legally - a shop can't add refrigerant to a system unless they find and fix the reason for loosing refrigerant. How strictly that law is followed is questionable.
Not likely, and not logical. At least not at the Fed level. Maybe at some particular State level if you want to read each State's regs.
Otherwise you can add refrigerant to locate a leak.
What you must do afterwards is properly contain or re-use the refrigerant when you remove it from the system.
EPA Auto Referigerants "In some cases, the technician will need to add refrigerant to the system to detect a leak."
It's the same as any other car. Hook up the gauges and manifold and add until the pressure is up to spec. The high side pressure is temperature dependent and is what you should fill to. For frame of reference at 27.5C, you're looking for 12-15.8 bar of high side pressure. I charge extra standard unit conversion. These are 4 zone numbers.
Lastly, if the system is still pressurized as your post indicates, then vacuum evac is not required.
If the Cayenne has an expansion nozzle like BMWs, those can become plugged over years of use. Replacing one requires depressurizing the system. replacing the expahsion valve, replacing the dryer (has to be replaced if any A/C hose is removed), and reinstalling the correct amount of R134. The BMW expansion valve isn't much more than a tiny hole... pressurized coolant goes in one end and the diameter of the hole is so small the liquid is atomized and expands rapidly, cooling it signifiantly. As this hole gets more and more plugged up over time, you lose cooling. In BMWs, you lose the cooling on the passenger side first and as the expansion valve gets more and more plugged up, even the driver's side stops getting cool. A pressure check may or may not show a problem. I don't know if these systems have a similar expansion valive or not.
I have a very accurate digital thermometer (Fluke 51II). I can stuff the thermocouple into one of the vents.
What temperature should I expect to get?
I would assume that would be relative to ambient air temperature.
I'm in Florida and it has been in the lower 90°s F here and it takes a good 10 to 20 minutes to get the cabin temperature down to comfort level with a sunny day. That seems a little anemic to me.
I'm in Florida and it has been in the lower 90°s F here and it takes a good 10 to 20 minutes to get the cabin temperature down to comfort level with a sunny day. That seems a little anemic to me.
Vehicular cabin temperatures on a hot sunny 90° day can easily reach 140°F; usually a temperature rise of 8-9°F per 10 minute increments, easily reaching 140°F after 45-60 minutes.
Upon start-up, the indoor sensor will sense the Delta-T between the temperature setpoint and the indoor temperature and will revert the system to maximum output; which means that it will go into 100% recirc mode. Recirculating 140°F air-on rather than 90°F outdoor air-on will result in higher suction pressures and a much longer pull-down cycle.
Rule of thumb is to open your windows and drive approximately 5-7 minutes with the A/C compressor engaged before closing them.
It's a bit complex.. and Andy - on the 958 series - when it powers up in a hot interior it doesn't go into "MAX-AC" - the recirculation flapper isn't opened, it still draws in outside air. It does however max out the fan speed, and set up so the chest level vents and the rear vent system get the majority of cooled air. My guess is people feel cooler when cooler air is blown at them..
This thread motivated me to see what I could find out about my HVAC using the iCarScan tool. Turns out - I learned a lot.
When I had my Variocam adjusters replaced last September - when I got the Cayenne back ('11 CTT with 4-zone HVAC) it seemed the AC was a bit less powerful than it had been prior to the work being done. Since the work ended up requiring R&R of the engine - which means sucking the 134A out of the AC system and then refilling it - my thought was - they refilled by weight, and didn't take into account the difference between the 2 zone capacity and the 4 zone capacity.
Looks like I was right.
The iCarScan can read out several interesting "real-time" streaming data.
- Input air temperature (ie - the ambient air temp as measured by the exterior sensor)
- The evaporator temperature
- The output temperature at the chest level dash vents.
- Engine speed
- The high pressure in the system
Using these - and the factory service manual - I was able to determine the system was a bit low on 134A, and topped it off - improving the performance.
There are charts in the service manual showing two important things:
1. The expected output temperature at the face/chest level center vents vs the ambient temperature
2. The expected high-pressure reading at different ambient temperatures
To do the readings - it requires a 5 minute warming up cycle - then switching the system to MAX output with the drivers and passenger windows down - and reading the high-pressure, comparing the expected value to the value read - all at 120 seconds after increasing idle to around 1,500RPM (diesel) to 2,000RPM (6-cylinder) and 1,900RPM for the V8.
There are two different charts given - one for 2 zone, one for 4 zone.
Given this data - it was a piece of cake to get the numbers correct, without the need for external gauges. I have no idea if the 955/957 system has the capacity to do this or not, but all the 958 systems do.
2 zone center vent temp
2 zone pressure reading
4 zone center vent temp
4 zone pressure reading
Process
Process Continued
Dunno how applicable these charts/numbers are to the 955/957 series - but I suspect fairly applicable. The pressure readings/cooling capacity are mostly a factor of the gas being used and the size of the system. At least these would get you to within a reasonable range.
Don, it's nice to see that PAG engineers bypassed this feature on the 958. Not having control on using outdoor air vs recirc doesn't make any sense at all and should always be a user-defined feature by default.
Most of the problems arising from climate control systems stem from technician inaptitude resulting in misdiagnosis. The omission of a sight glass or liquid indicator on most modern vehicles has them stumped even more so and has placed too much of a dependency factor on the automated Snap-On or BluePoint A/C charging unit. I've personally witnessed technicians pumping in copious amounts of refrigerant oil as a norm whenever re-charging a system.
I'm not sure about the 958 however, most of the multi-zone systems that I'm familiar with required activation of all the zone controls (solenoid valves or control valves) when evacuating the refrigeration circuit with a vacuum pump. Failure to open these valves during evacuation usually results in trapped air/moisture and can cause higher than usual system pressures. Most modern vehicular climate control systems now use a combination of variable fan speeds, mixing/diverting flaps and mixed warm air from the heater core to regulate each independent zone.
In short, unless you really know what it is that you're doing, leave it to the experts.
On another note, and simply to add to Deilenberger & Griffith's discussion regarding system leaks, it is against Canadian law to replenish any refrigeration or air conditioning system with refrigerant; unless the leak is found and repaired. This is governed on a Federal level and is strictly enforced by both Federal & Provincial authorities.
Simply put, physical logs showing refrigerant purchases and sales must be readily available to the Feds upon request.
FWIW - I also found a secondary problem with my 958 HVAC. It still wasn't quite up to snuff.. the high-pressure was lower than the charts told me it should be, and the air coming from the vents wouldn't give me a cold induced headache like my 955 would.
So I hooked the iCarScan up and looked for faults again. I found several that repeated themselves - one was the recirculation flap apparently didn't always respond, the other was the blower supposedly triggered the over-current protection circuit.
I went though the re-sync of the stepper motors - they all passed their tests except the recirc one. And listening to the blower noise when pressing the recirculation button - sometimes the noise changed - sometimes not (gets a bit noisier in recirculation mode.) So - I thought I would feel around the blower and see if I could feel the flap (which I assume is simply a door that opens to the housing - opening a passage inside the cabin and closing the outside passage when recirc is selected.)
As I kneeled down on the passenger side - I realized my hand was wet. Quite wet actually. Then I looked and could see water dripping out of the panel under the glovebox. So I removed that panel and found water dripping out of various spots on the HVAC box - most from around the cabin filter door. I removed the filter door (with a tray under it to catch any water) and found the bottom 2" of the filter was wet. Took out the filter, and set it aside to dry.
I then ended up removing entirely the rubber drain hose. It simply pushes through the firewall with a built-in sort of grommet, and pulls over the drain spigot from the HVAC box. Problem is - the end on the HVAC box is held on with one of those devilish squeeze to release hose clamps. It took a bit of effort to get that side loose. When I did - more water came out (caught in a tray.) Altogether I think I drained roughly a quart from the HVAC box. I cleaned out the rubber drain hose - and made sure the little flap on the end opened - reassembled everything - and checked operation.
Much better! The recirculation flap now passes all it's tests and responds reliably to the recirc-button. The high-pressure reading is now exactly in the middle of the high/low range noted in the charts above, and the air coming from the vents is almost headache inducing cold (especially at 2K RPM or above - where the system apparently puts out peak output.)
Meanwhile - I mopped up the carpets - soaked several big bath towels squeezing water out of the carpeting, and hung my carpeted mat up to drain - about another quart came out of that.
I'm heading over to the 958 section to see if anyone has pulled up their carpeting to dry out the footwell. It was fairly easy to pull up on my 955 (especially after doing it a dozen or so times due to various floods) - but it is one piece from the floor up onto the seat pedestal. I seem to recall a seam there on the 955 that made it easier to get up high enough to get under all the wet foam rubber.
Take it to Porsche. My '06 started to go bad while my wife was visiting family in Florida last year while I was deployed. It was less to fix/recharge that than it cost for the oil change at the dealer IIRC, they recharged the AC (and a year and a half later is working fine) for less than $150, at Porsche of Destin.
Pick up a small 12oz can of 134a...currently $3.97 if you have a Menards near you.
Set the controls to center vents, fan on high and temperature to LO. Go for a short drive and then head home and take a temperature reading at the center vent while at ~2000 rpm.
If it's warmer than 45° add about ¼ of the can to the low side fitting and see if the temperature drops. If it does, add a bit more until you're around 38 to 40° and call it a day for about $4 bucks.
If you don't see a drop after adding the first few ounces, you most likely have other issues behind the dash.
Do NOT buy any refrigerant that claims to have "leak sealer" in it!
06-25-2017, 10:40 AM
955 AC Recharging???
