Intake side of this evaporator is clogged with debris. The result is a decrease in air flow efficiency through the evaporator. Cooling suffers from this. Bottom photo shows same evaporator after having been properly cleaned.
Something not right inside your Porsche's cabin? Whether AC, seating, headliner, dashboard, electrical or cosmetics, you've got 30+ years of Porsche expertise right here to answer your Porsche's interior needs. In Miami, the #1 cabin interest is... AC.
Porsche interiors speak eloquently of moments in time. Below, a look at Porsche interiors, a 1954 356 compared to a 1974 911, 2014 918 Spyder, and 2020 911.
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Below are notes for each component shown in the Porsche AC diagram shown above.
1. Compressor - Basically a pump. There are both electrical and mechanically driven units with mechanical (belt driven off the engine's crank pulley) being most common. Compressor's purpose is to circulate refrigerant ---creating a low pressure on its GAS/VAPOR side of the system, and high pressure on the LIQUID side. If pressure differences are not correct, your Porsche's AC will not perform to capacity.
2. Rear Lid Condenser - Transfers cabin heat absorbed by the refrigerant to the outside environment. This thermal exchange is done on the high pressure / liquid side of the AC system. Condensers must be both clean and have sufficient air flow through them to work efficiently. Porsches typically have two stock condensers. One mounted in the rear engine lid. The second mounted at the front of the car between the bumper and fuel tank.
3. Fender Condenser w/Fan - It's not unusual for Porsche owners to add a condenser unit to increase the thermal efficiency of their AC system's condensing process. The most productive added condenser is a left rear fender unit that must include a fan blowing through the condenser towards the engine. Front fender units can also be installed provided there's space.
4. High Pressure Side - Liquid Hose - Transports compressed, hot refrigerant liquid from the compressor at the rear of a Porsche, through the condensers, to the front of the car through the Receiver/Drier (RD) and to the Thermal Expansion Valve (TXV). Old system hose is typically non barrier-hose meaning it's permeable to a degree. This type of hose is prone to leak-through thereby progressively degrading the cooling capacity of a Porsche's AC system. For optimal continuing performance, it's advisable to replace old hose with contemporary "barrier hose." All replacement hose must be installed correctly, most importantly to protect it from exposure to road damage. Your Porsche itself must be mechanically handled in a manner respecting your AC hose---among other parts---that may be damaged from inappropriate handling. This happens when inexperienced mechanics attend cars they're not familiar with. Good reason to entrust your Porsche to a Porsche specialist that has published credentials.
5. Front Condenser - This is the second condenser in the stock Porsche AC condenser arrangement... the third in line where a fender condenser has been added.
6. Receiver Drier - Collection area for liquid refrigerant prior to the refrigerant going to the Thermal Expansion Valve (TXV). In addition to serving as a refrigerant reservoir, R/Ds include desiccant within them. Desiccant serves a critical role in trapping what minimal moisture may exist within a system and doing so just prior to the refrigerant going through the TXV. This moisture trapping is important to prevent the TXV from freezing---as it can do when too much moisture (water) is in with the refrigerant. There should be NO moisture in the system but this is not always the case. Moisture is removed from AC systems by drawing a vacuum on the system just prior to charging it with refrigerant. This vacuum & charging process is very specific so as to prevent moisture from returning into the system and so the correct amount of refrigerant is introduced into the system. Receiver driers also serve as filters, debris being trapped in the desiccant area.
7. Thermal Expansion Valve (TXV) - Valve that meters the flow of refrigerant released into the evaporator. On one side of a Porsche's TXV there is high pressure. That is the liquid side. To work, a TXV monitors your Porsche's AC system's low side temperature & pressure. TXV manufactures set the parameters for a TXV's operation so there is no need for adjusting a TXV prior to or after install. When a TXV releases refrigerant into the evaporator, which is the low pressure side of the AC system, the refrigerant instantly evaporates inside the evaporator due to the LOW PRESSURE within the evaporator. The genius of AC is basically a loop where there is a low and high pressure side where pressures & temperatures are are harnessed to create cold via the process of evaporation.
8. Evaporator - Directly after and connected to the TXV, this unit is designed to accept the evaporating refrigerant from the TXV and, as Porsche cabin air passes through the evaporator, the cold of the refrigerant within the evaporator is absorbing the heat that exists in the air passing through the evaporator. So warm air enters the evaporator and cold air exits it (then going through your Porsche's AC ducts and back into the cabin via the AC vents.) For an evaporator to work efficiently, a few things must be in order. First, the system must be charged with the correct amount of refrigerant in order to optimize high & low side pressures. The compressor must be working correctly in order to create correct high and low side system pressures to drive and suck refrigerant through the evaporator. The TXV must operate correctly, releasing the correct amount of refrigerant into the evaporator. Evaporator and condensers must be clean in order for the thermal exchange process of both inter-related components to do their job. There cannot be too much compressor oil in the system or the oil will insulate the evaporator's insides. The evaporator's plenum (the box the evaporator sits in) must be in good order---not leaking air from cracks that come from age and/or mishandling. And there must be adequate air flow through the evaporator. In simple terms, where condensers rid your Porsche's AC system of heat, the evaporator does the opposite---it absorbs heat that goes into the refrigerant that eventually is expelled to the ambient (outside of cabin) air.
9. Low Pressure Side - Gas (Vapor) Hose - Transports refrigerant gas (vapor) from the low pressure side of the Thermal Expansion Valve (TXV), through the evaporator and back to the rear of the car to the compressor. At the compressor, the refrigerant's cycle begins again. There can be a pressure switch in the low side hose that serves to cut power to the compressor in the event AC system pressure gets either too low or too high. A Porsche AC pressure switch, if installed, is typically located in the low side hose near the compressor.
Refrigerant & Oil
Refrigerant - Within a Porsche AC system go both refrigerant and oil. R12 was used for many years but phased out for the purpose of environmental protection. Still, some Porsche AC systems continue to use R12 but those instances are increasingly rare. R12 can still be found albeit it relatively expensive. R134a was/is the replacement refrigerant for R12 and works well given a proper AC set up. The next refrigerant supposedly replacing R134a in all new cars by 2021 is R1234yf. The premise for this transition is R1234yf breaking up faster in the upper atmosphere as compared to R134a, and so contributing less to global warming. The promotion for R1234yf indicates it being easy to upgrade a car's AC system from R134a to R1234yf. As this is written, I continue to use R134a.
The key to refrigerant installation is eliminating moisture within the AC system prior to charging the system with refrigerant. Introducing the optimal charge/weight of refrigerant into a given Porsche AC system is also important. Too much refrigerant in a Porsche's AC---any AC---and the system is basically drowning. Not enough and the opposite occurs---the system starves. With the correct charge of refrigerant, there's always an optimal supply of liquid refrigerant within the Receiver Drier and so always an adequate refrigerant supply for the TXV. Correct pressures on both the high and low sides of an AC system provide the balance necessary for harmony within the system. All these factors are important to an AC delivering cold air out the vent.
Oil - For a compressor to endure, it must have proper lubrication. This lubrication is specific AC compressor oil that's put into the AC system according to compressor manufacturer's instructions for oil type and amount. Too much oil and the oil acts as an insulator within the condensers and evaporator preventing the proper thermal performance of a Porsche's AC system. Too little oil and the compressor will be oil-starved. When oil-starved, a compressor will progressively wear from internal friction. The end result is "black death." This naming comes from the fact that when looking at the fluid that exists within an oil-starved Porsche AC system, it's black in color. To maintain a healthy, durable compressor, the correct type and amount of oil is essential.
Leaking - For everything in an AC system to serve its purpose, an AC system MUST be a 100% closed system. This requires FULL integrity of EVERY component. Generally speaking, age is what wears most AC components out. Because of this fact, it can be said that no AC system will cool a Porsche cabin indefinitely. Eventually something will give---something will leak. If not from age, then for some other reason. The good news is leaks can be found and fixed.
Porsche AC performance - What can you expect?
Some say older Porsche AC systems are incapable of delivering cold air due to those AC systems being engineered as "afterthoughts" for the car. This may be true in part however, the basic AC parts of a 911 Porsche PERFORM WELL when ALL parts are in good form and the system is set up correctly. If your Porsche's AC system is not performing to your satisfaction, schedule with me to bring your car in. I'll have a look at your car's AC and advise you what's required to return it to good cooling form.
Porsche AC Optimization: Sample
Below is test info gathered from a customer's '80 911 (with an '85 engine.) This Porsche's AC system is an example of every component being in proper order and the system set up correctly. Component-wise, it has barrier hose throughout and an added fender condenser with fan. Air flow through the rear lid condenser has been optimized by: ensuring the stock engine seal is fully intact and correctly positioned; adding a foam seal to that condenser's perimeter between it and the rear lid; putting a foam seal in the gap between the rear suspension cross-member and tub; putting a foam seal around the engine bay lid. Optimal thermal exchange is guaranteed given all condensers and the evaporator being clean. The thermostat sensor is at the perimeter of the evaporator, not at the core. The system is charged correctly with oil and R134a. All fans and blowers are working. A view of the evaporator's intake side is provided by an endoscope camera positioned in evaporator's plenum . This camera allows a real time view of the evaporator to inspect the extent of the frost accumulating on it when the AC system is running. Some frost is acceptable. Running an AC system with the evaporator below freezing for too long in humid climates---as we have in Miami---results in a block of evaporator-ice. This cuts off air flow through the evaporator and so to the cabin. The info-images shown below were taken a few minutes after the system was turned ON. As this AC ran, cabin temp continued downwards to the 70 degree F target. What's important to see here is the "dash vent" temp being just above 30 degrees F with the outside ambient air at 88 with 64% humidity. Note the cabin humidity having dropped to 45%. This is the evaporator both cooling and drying cabin air.
To get heat out and cool into your Porsche's cabin, the AC system needs to have all components working correctly. One area not in proper order drags the whole system down. The result is a slow---or abrupt---decline in cold air coming from your AC vents. To better understand your Porsche's AC system, below is comprehensive reference to a 911 AC system's main components. Regardless of what Porsche you have, basic parts and principles of auto AC are the same. If AC is a mystery to you, it won't be after going through the information provided below. If AC is of no interest to you, click here to jump to the next section on this page, Porsche Seating.
Bottom line, a Porsche air conditioning system that's not performing well can be brought back into good cabin cooling form. What effort/expense is necessary to do so depends on where a given AC system stands. Most often, lack of performance is due to a leak. The result is a lack of refrigerant and either the compressor is working and there's minimal or no cooling, better still the pressure switch has cut power to the compressor due to low system pressure. In this case, it's a matter of locating and repairing the leak, inspecting the entire AC system if a customer decides to have this done, then if all's in order, proceeding with the process of recharging the system. If an air conditioning system has been neglected for an extended period of time---let's say years---any number of areas probably need to be dealt with to return the system to good cooling order.
Air Conditioning System Preservation
AC systems need attention on occasion in order to continue cooling as intended. The more often servicing is accomplished, the less that needs to be done at each servicing. The benefit in consistent AC attention is the system being preserved to function as it should. Neglect typically results in a progressive decline in cooling. Then, a good deal of work to bring the system back to order. The "best way" to go is the way an owner chooses.
AIR CONDITIONING BACKGROUND:
While the principles of evaporative refrigeration have been known for centuries, the fundamentals of mechanical (artificial) refrigeration were first discovered and presented by William Cullen at the university of Glasgow in England in 1748.
In simple terms, refrigerant is used to move heat from one place to another. In the case of a car, this means from the cabin to the outside environment. The diagram at right shows a Porsche's AC refrigerant system. A third condenser in the driver's side rear wheel well is added for improved heat evacuation efficiency.
HOW AC WORKS:
Starting with the compressor as a pump, refrigerant is pushed and compressed in the high pressure side of the system (red line in diagram at right) and on through the condensers. Heat captured in the gaseous refrigerant is transfered to the atmosphere via the condensers. As this occurs, the refrigerant progressively condenses into a liquid. Once in the receiver / drier, the refrigerant is fully condensed into a liquid and any moisture in the system is trapped by a drying agent contained within the receiver / drier unit. Entering the evaporator the liquid refrigerant is turned into a vapor by the thermal expansion valve. This conversion of the refrigerant from a liquid on the high pressure side to a gas on the low pressure side causes a drop in temperature throughout the evaporator. As warm cabin air is circulated through the evaporator by the AC's blower, the refrigerant gas inside the evaporator captures and stores heat from the cabin. What we feel in the cabin as a result of this activity is the cold given off by the evaporator. Heat laden refrigerant gas is sucked back to the compressor (blue line) to begin the cycle again.
The challenge with AC systems is to correctly charge a given system with just the right weight of refrigerant. Too little and the system will not cool to it's full potential. Too much refrigerant results in high internal system pressure---stressing components. Just the right amount of refrigerant and... maximum cooling is achieved with acceptable operating pressures.
Adding a rear fender condenser with fan is typical modification to Porsche's stock 2-condenser 911 AC system. This increases condenser surface area. Doing so allows more heat to dissipate from the system to the ambient atmosphere. This is a Kuehl unit.
AC pressure switch protects system from too high or too low pressures by opening the electrical circuit that engages the compressor's clutch. If an AC is turned ON and the cabin blower is working but there's no cold air exiting the vents, AND the compressor is NOT engaged, the pressure switch may well be doing what it is designed to do. If this switch is jumped and the compressor engages, AC system pressures may be incorrect or the switch may be bad.
Top photo shows new Sanden AC compressor with the head cap removed. Below that is a similar Sandan unit also with the head cap removed showing what happens to an oil starved compressor. This is a "black death" compressor. The black is metal that the pistons used to be comprised of. Once pistons wear to the point of wobbling in their cylinder, their o-rings escape and progress through an AC's plumbing.
PHOTO CREDIT: GRIFFITHS
AC hose cut in half shows how system oil sticks to the interior walls of the hose. With a 911 having approximately 40' of hose, a good deal of system oil is given to this coating.
AC system being flushed. These are metal particles that are shedding from the interior walls of an old condenser.
Where interior refinements and/or restorations for the street are concerned, I look to you to say what you want to achieve with your Porsche's seating. For instance, when refining... quite often this involves seat reformation---going from a non or slightly bolstered seat to a highly bolstered seat similar to a 930 sport seat. You can define the look you're after by providing visual reference. Choose the material you like... and provide me samples if you can. I and my "seat team" will create your seats... just the way you want them. Or, I can install seats bought off the shelf. Before buying seats, I recommend ensuring the seats you plan on purchasing do indeed fit your Porsche without question. The seats manufacturer should be able to answer this question for you. Be cautious about taking a seat retailer's confirmation on this as they may get it wrong.
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Air conditioning system oil samples. On left is new oil. On right is oil just taken from an operating Porsche AC system. These samples demonstrate a Porsche AC system in excellent operating form.
Over time, condensers loose efficiency due to their exterior surface accumulating a coating of insulating debris. On occasion, it's beneficial to inspect for this accumulation. Then, decide if the thermal performance of the AC is worth attending to condenser cleaning.
If your cabin air has a musty odor, first check the carpeting. If the carpeting is in good order, check the air coming from the AC vents. It's possible the AC system has mold & mildew in the ducts. There are sprays that can be put into AC ducts but the results are always questionable. The one way to ensure a thorough cleaning is to access the ducts and remove all the mold & mildew.
This is the shifter coupling that's just ahead of the bulkhead to the engine bay in a 911. The seal around the shifter rod must be in good order and in proper position... for the AC to work well. If this seal is failing or not in position, the AC is sucking some measure of hot air from the engine bay.
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Above: Customer Sport Seats in for a comprehensive rebuild. Owner's special request: seats covered in full grain leather... not top coated leather which is commonly used. Full grain leather's surface is the genuine hide whereas top grain leather is coated. This coating is done to minimize/hide blemishes and to create a consistent appearance across batches of material---a treatment done for commercial purposes. Lost in this top coating process is leather's natural silky feel and the patina achieved over time given adequate care. For this rebuild, we've stripped these Sport Seats to the bone. Metal will be rust reformed & painted, errors in engineering corrected, mechanisms will be blasted & refinished, and new support bottom & back will be installed along with new tilt cables. Side bottom bolsters---which can be counted on to wear before anything else due to seat entry & exiting scrubbing---are made independent from center cushion. This allows them to be easily replaced in the future. Steering wheel is recovered using same leather.
Below: Owner was creative in preventing cracks in these leather seats from propagating. Various leather patches were applied using flexible epoxy gel. At right is the same seat after being treated to entirely new leather covering. The passenger's seat was not quite as patched as the drivers but it to saw new covering. With seating contributing significantly to a Porsche's interior look & feel, new leather covering makes a dramatic impact on interior quality. These are "Standard" Porsche seats.
With age, headliners naturally become brittle and will eventually break under the lightest touch. GP replaces headliners with quality material that will last many-many years. And in the doing, special care is taken to ensure the outcome equals Porsche's factory installation. While replacing headliners, it's an efficient time to service other areas, particularly where a sunroof exists. This is because the sunroof must be removed for a headliner replacement. Sunroof's motors, cables, and the roof drains are now easily accessible. A smart time to inspect, lubricate, and clear roof drain channels. Sunroof seal replacement can be considered... and done if needed. This is a good example of how work in one area can translate into "efficient work" in other areas. This does add to immediate costs. The benefit being an area not having to be returned to less efficiently downstream.
photos to enlarge
Old headliner was cracked and falling to pieces . New material is positioned to retain all systems in working order---temperature sensor and sunroof most notably. With this headliner, sunroof cables were lubricated, motors inspected, drains reamed of debris, new plastic jams installed, tired air dam was made to rise fully, missing rubber dam bumpers were installed, trim was polished, and new roof seals front and rear were installed. Was all this necessary to do? No. Was it practical to do now? Yes.
Variety of cabin repairs are in progress here. Areas being attended: electrical, AC ducting, dashboard, sunroof, headliner, audio, seating... you name it, it's likely on this Porsche's to-do list. Mission in hand is to restore all systems so they'll not only work but also be durably reliable. Cosmetics are also attended. When all's said and done, the cabin will work like new and have a beautiful interior with a slight patina. Before & after photos shown.
VIDEO BY: PORSCHE®
Porsche® Onboard footage -
Record Run 918 Spyder
Video presentation courtesy of Porsche N.A. Permission on file.
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A quality Porsche experience relies on controls and interior systems being in working order. And materials from leather and vinyl to hard & soft rubber retaining form, color and pliability. Time is a relentless foe. More so when a Porsche is truly enjoyed. AC's leak. Leather cracks. Headliners sag. Switches, bulbs, bushings, electrical connections... all of it degrades from intended use. If your Porsche's interior can use a simple fix, or, needs significant attention for street or track, 30+ years of Porsche expertise is in your hand. A simple call... Interior problems solved.
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Porsche, the Porsche crest and Porsche model names are the property of Dr. Ing. h.c. F. Porsche Aktiengesellschaft, Porsche AG ("Porsche") and is under licensed use by Porsche Cars North America, PCNA. The PCA logo is the property of the Porsche Club of America. No affiliation with either Porsche or the Porsche Club of America is intended or implied by GP AutoWerks, an independent Porsche service, repair, rebuild & PPI shop located in Miami, FL., U.S.A. Any use of the word "safe" or "safety" in this mobile site holds a car's owner and/or driver ultimately responsible for all matters concerning the operational safety of the car being driven or otherwise used. Please see desktop website for full disclaimer and credits.
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