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Air Conditioning Recharge
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Pelican Technical Article:

Air Conditioning Recharge


1 hour1 hr


$25 to $750




Air conditioning pressure gauge, specialized AC equipment

Applicable Models:

Porsche 986 Boxster (1997-04)
Porsche 986 Boxster S (2000-04)

Parts Required:

R134a recharge kit

Hot Tip:

Don't use non-134a replacement refrigerant

Performance Gain:

Better cooling during the summer months

Complementary Modification:

Replace main accessory belt
101 Performance Projects for Your Porsche Boxster

This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.

On any car, the AC system is a complicated beast. This project is not intended to be a repair manual for your AC system, but to serve more as a guide on how the system works, and the maintenance involved with its upkeep.

Almost all air conditioning systems work on the theories of thermodynamics, whereby heat flows from a warmer surface to a colder one. Heat from inside the car is transferred to the cold metal fins of the evaporator. The refrigerant in the system picks up the heat from the evaporator and takes it to the compressor. The gas is then pressurized which concentrates the heat by raising the temperature of the refrigerant gas. The gas is then sent to the condenser. The condenser cools the refrigerant and turns it back into a liquid from a gas. The liquid is then sent to the receiver-dryer, where any water vapor that may have formed in the system is removed. The receiver-dryer also acts as a storage container for unused fluid. From the receiver-dryer, the liquid flows into the expansion valve, which meters it into the evaporator located inside the car. Here the liquid absorbs heat, and becomes a low-pressure gas. This evaporation, or boiling of the refrigerant, absorbs heat just like a boiling pot of water absorbs heat from the stove. As heat is absorbed, the evaporator is cooled. A fan blows air through the evaporator and into the cockpit of the car, providing the cooling effect.

The compressor pumps the refrigerant through the entire system. An electromagnetic clutch on the compressor turns the AC system on and off. In addition to cooling the car, the system also removes water vapor from the ambient air via the cooling process. It is not uncommon to find a small puddle of water underneath your car from the condensation of the air conditioning system. A thermostat control on the evaporator keeps the condensation in the evaporator from freezing and damaging the unit.

So what can be done to maintain and protect the system from deterioration? First and foremost, the air conditioning system should be operated at least once a week, if the outside temperature is above 50 degrees Fahrenheit. This will circulate the refrigerant in the system, and helps to keep all the seals in the system from drying out. Most failures are caused by refrigerant leaking out of the system and can be prevented by making sure that the system is run frequently.

The belt that runs off of the main crankshaft operates the AC compressor. If you think that you might be having problems with your compressor, check the condition of the belt first. Turn on the system, and check to make sure that the electromagnetic clutch is engaging. If not, then you may need to replace it. Check the power connection to make sure it is live before replacing. The system also has a pressure switch located right next to the high pressure port in the front cowl area which will shut it off if the pressure inside the system is too high or too low. Check the pressures in the system, and/or the operation of this switch if you're having A/C problems.

On the 1997-00 Boxsters, there is also a set of diagnostic codes that the AC control unit can output, to aid you in diagnosing problems. Check the website for more details on this.

Refilling AC Systems

The biggest problem with AC systems is a loss of refrigerant. Luckily, the replacement and top-off of refrigerant is a relatively easy task. All Boxsters use R134 refrigerant which can be can be purchased inexpensively at your local auto parts stores. The Boxster air conditioning system capacity is 850 grams (30 oz) of R134. In addition, the compressor needs a synthetic lubricant for proper operation. If you're filling a completely empty system, add 195 ml (6.6 oz) of ND 8 refrigerant oil.

The kit I used to refill the car in this project is manufactured by Interdynamics (see Figure 1). Start the car outside of your garage, turn on the AC system and fan to full blast, and let the car run with the system on for about three minutes. Following the instructions included with the kit, connect a new can of refrigerant to the hose/gauge assembly. Connect the gauge assembly to the low-side port on your AC system (see Figure 2). Be sure to wear eye protection and heavy leather gloves when handling the coolant and gauge assembly: if coolant leaks out at any time, it can freeze a small patch of skin on your hands quite easily and give you frostbite.

With the car running and the AC system turned on full blast, take a reading on the pressure gauge. If your system is properly charged, it should read between 25 and 45 psi. If the pressure is low, then turn the valve on the can to release more refrigerant into the system. Be sure that you shake the can for about 30 seconds and turn it upside down when you connect it to the gauge assembly. Also be aware that the pressure gauge reading will automatically elevate as you are adding more coolant - periodically close the valve on the can to check if the pressure is rising in the system. If the pressure doesn't increase after adding one complete can, then you most likely have a major leak in your system, and you should seek the help of an AC system professional mechanic.

With the system properly filled and measured with your gauge, you should head to the passenger compartment and check the temperature of the air exiting the vents. On a system that is operating really well, the temperature will be in the mid-thirties Fahrenheit. For systems that are older and weaker, then the temperature readings will mostly like be higher. Also keep in mind that if your system is cooling air in the 30 degree Fahrenheit range, the compressor on the car will tend to turn itself on and off, and the temperature will rise up and down slightly. This is not a defect of the system: the compressor turns itself off as the temperature in the evaporator nears the freezing temperature of water. This prevents the evaporator from becoming frozen and clogged with icy buildup.

Shown here is a great starter AC kit from Interdynamics.
Figure 1

Shown here is a great starter AC kit from Interdynamics. This kit contains three cans of R134a refrigerant and oil, and is specifically designed to replenish older cars that may have a few small leaks in the o-rings of the air conditioning system. Included with the kit are a can adapter valve, an in-line pressure gauge, and several adapters that are not required for use with the Boxster. The kit is available for about $35 at most general automotive stores, and contains everything that you need to recharge your R134a air conditioning system.

This photo shows the location and orientation of the AC ports on the Boxster.
Figure 2

This photo shows the location and orientation of the AC ports on the Boxster. The AC ports are normally covered with plastic covers that simply screw off (inset). The low-side (the side that you attach the gauge and refrigerant to) has the smaller port adapter, and is attached to the larger pipe (yellow arrow). The high-side (used primarily for checking the compressor during diagnostic testing) has the larger adapter (green arrow), and has a smaller diameter pipe.

With the engine running and the system engaged, connect the gauge to the low-pressure port on the AC system.
Figure 3

With the engine running and the system engaged, connect the gauge to the low-pressure port on the AC system. The high-side has a larger adapter, so that you can't accidentally attach the gauge to the wrong port. With the gauge attached, you can now turn the valve to add more refrigerant to the system. In the photo inset, you can see that the pressure for this AC system is exactly where it should be: in the middle of the white range. Remember to use heavy-duty leather gloves and eye protection when working around AC components: it's possible that a fitting or a valve may break or leak refrigerant on your hands.

Your hand is a pretty poor indicator of relative temperature.
Figure 4

Your hand is a pretty poor indicator of relative temperature. In order to get an accurate reading, I recommend that you use a digital thermometer, like the one shown in this photo. Final temperature performance of your AC system will vary based upon a number of factors: age, quantity of refrigerant in the system, the condition of the compressor and associated components. This car is a 1999 Boxster with 80,000 miles on the odometer. The vent reading is 46° F (8° C) with the AC at full blast. Outside temperature when this reading was taken was probably around 70 degrees Fahrenheit. You should expect at least about a 20 degree drop from the outside ambient air.

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Comments and Suggestions:
winair1 Comments: I am having an AC issue and hvac unit not turning on all the time. i have no cold air blowing and checked all the fuses and replaced the HVAC controller. nothing changed and fuses are good. the hvac controller doesnt come on once in a while but when i turn off car and turn back on it comes on. the AC compressor doesnt sound like its coming on but fuses looked good. the air itself seems to kick up and down but no cold air and i dont hear AC compressor running i dont think. i see people say it could be a relay and i hope its that inexpensive of a problem. i saw a diagram here from nick but not sure what part number i need to order to try that fix before i have to take in for a lot more money. please help. email and let me know what i should buy so i can get here before the weekend
October 18, 2016
  Followup from the Pelican Staff: Are you having two issues, one being no cold air and the other being blower speed not correct? If so, check a/c system pressure to confirm it has a good charge. Then check if the blower resistor is faulty.- Nick at Pelican Parts  
TJ Comments: I have a 1999 Boxster. I noticed a post that mentioned black foam was coming out of the air vents This is happening on my car. Does anyone know where it might be coming from or what is falling apart?
August 24, 2016
  Followup from the Pelican Staff: Most likely the insulators for the evaporator or the seals for the heater housing doors. - Nick at Pelican Parts  
Vic the skier Comments: My 05 boxster 2.7 air con compressor is not running, the gas pressure, relay and fuses are ok what is the next most likely culprit?
April 12, 2016
  Followup from the Pelican Staff: The compressor, if all else checks ok. - Nick at Pelican Parts  
Rodolfo Comments: Do you have a diagram for the front relay support?
Porsche Boxster 1997
December 8, 2015
  Followup from the Pelican Staff: I don’t have that info.

I would grab a repair manual. It will have the procedure, special tools and torque specs.
- Nick at Pelican Parts
Chas Comments: Occasionally I get a drip on my foot on humid days. How do I find the drainer pipe ? Can I get to it from inside ? Remember our drivers side is on the right side. As it should be !!
September 22, 2015
  Followup from the Pelican Staff: It is at the center of the vehicle, near the battery. - Nick at Pelican Parts  
Bernard Comments: porsche 996 2000 . ac working but not cold enough. 15 degree difference with outside and not good in Florida. I cleaned the evaporator which was molded , changed blower, changed both fans they are working very hard in Florida checked pressures low 45 high 200 @ ac on low and @ 2000 RPM . I clamped the how water to the heater no difference and I can hear the flaps inside working some time ago the vents have been blowing pieces of foam though.
what else can I do? Flush? renew dryer and expansion valve? or new evaporator? If I renew, vacuum....where do I put the oil in and flushing with what and from which line? reverse or along the flow of the system?
August 24, 2015
  Followup from the Pelican Staff: With a low side of 45 I would expect to see the high side about 25 pounds higher. I would check if the charge is low. - Nick at Pelican Parts  
drummer Comments: according to interdynamics most vehicles from 1994 to 2015
don't need a specific adaptor to recharge the a/c. their
kits are now just a can with a universal attachment. part #acp-100
July 30, 2015
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
drummer Comments: I talked to bob at pelican parts and was informed that pelican parts does not sell the interdynamics a/c recharge kit shown in project 97 of 101 projects for your boxster. does any one know the interdynamics part #. I have not been
able to find this kit at my local parts suppliers. thank you
July 30, 2015
  Followup from the Pelican Staff: You may not need an adapter.

I opened a post in our forums. A Pelican community member may be able to answer your question. - Nick at Pelican Parts
drummer Comments: do you sell the complete interdynamics kit? hose and gauge
as well as adapters and 134a refill canisters for a 99 boxster?. I notice a few parts on your site like an adapter.
I don't want to get a kit with the wrong a/c adapters for my car
July 28, 2015
  Followup from the Pelican Staff: I don't think we have that kit. - Nick at Pelican Parts  
MikeRun5 Comments: Thanks again for the info. When you say check control unit faults do you mean use piwis? If yes, as I am completely unexperienced on this matter, please let me know what I need to look for, there are a lot of tasks available for this model of car, Thank you
July 12, 2015
  Followup from the Pelican Staff: Yes, or a comparable Porsche scan tool. - Nick at Pelican Parts  
MikeRun5 Comments: Hello again, about my previous question I checked fuses and turn on possition as you told me, all seems ok. As ac control panel continues to not function at all I removed the panel an here is a point that can mean something: panel is wired with a black plug and red plug, if I unplug black one fan starts to blow, with black plugged it not. In any case ac panel continues to not turn on or work. Hope you can help with this particular issue, Thank you
June 18, 2015
  Followup from the Pelican Staff: When the control panel goes down, the default safety protocol is to run the fan with the heat on and defrost vent open. That is why this happens. I would check the faults in the control unit now that you have all the basics covered. If there are multiple faults clear them and see what returns. Then we can figure out a logical plan of attack. - Casey at Pelican Parts  
MikeRun5 Comments: Hello, my Boxster S ac control panel do not work, nothing went wrong with ac never, I removed battery for a long stay without using car and with battery connected again control panel do not work I push the buttons and nothing happens, no air flows trough vents at all, any idea what happens? Thank you
June 10, 2015
  Followup from the Pelican Staff: First check all fuses. If fuses are good, turn the key in the ignition switch slightly to the right or the left of the "ON" position and listen to see if the fan starts to blow. This is a common indicator of a failing ignition steering lock assembly. - Casey at Pelican Parts  
Jeff Comments: I have a 99 Boxster blowing warm air. I've recharged the system. Neither of the supply and return lines are cold, both stay warm when the AC is running. The compressor does engage, in as much as it drags the engine down when I turn on the Auto setting on the control panel. I've heard this may simply be a relay or a bad compressor. I cannot find which relay controls the AC system, I thought I'd change that out first before I got any deeper into the system. Do you have any idea which relay I would change?
April 20, 2015
  Followup from the Pelican Staff: If the compressor actually does engage, the relay can be assumed to be functioning properly. To answer your question though, the A/C compressor relay is in the rear luggage compartment on the left side. If I remember correctly it is the Green relay. I've attached the diagram. Just curious though how did you recharge the system? What were the high and low side pressures after charging?
- Casey at Pelican Parts
Lucky Comments: Would you consider replacing the A/C compressor on a Boxster a DIY job ?
July 22, 2014
  Followup from the Pelican Staff: If you have a way to evacuate and recover the refrigerant, yes. It can be done easily after that. - Nick at Pelican Parts  
Chad Comments: The air blows fine in my 01' Boxster, but when I turn the air on, I get no change in temperature. Will this likely fix that problem?
July 8, 2014
  Followup from the Pelican Staff: You may need to have the system leak tested and recharged. - Nick at Pelican Parts  
Rick Comments: I have a 1999 Boxter, with the AC turned to low and the fan to high it will not take any refrigerant what could be the problem?
July 4, 2014
  Followup from the Pelican Staff: The system could be full or have a restriction. - Nick at Pelican Parts  
polly Comments: how do I remove the AC underbody pipes from my 986 Boxster S as they are damaged & how much for a replacement set?
May 26, 2014
  Followup from the Pelican Staff: You will have to remove the fender and under body panels that the lines run through. Discharge the A/C, then swap out the lines. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
gale2238 Comments: where is the electric plug located to plug in the compressor?
April 18, 2014
  Followup from the Pelican Staff: There s a pigtail that comes off the compressor. It should be attached to the top of the A/C compressor. - Nick at Pelican Parts  
Ray Comments: My 08 cayman is blowing only room temp air, I recharged using a similar kit, the R134 charges but there is a leak right near the low port, between the high port right at the back of the sensor that plugs in right there, not at the evaporator valve, just at the back of the sensor where the wires enter the connector, is there an O ring right at the sensor?
January 25, 2014
  Followup from the Pelican Staff: The sensor will have a seal. But to be safe, I would replace the sensor and the schrader valve under it (if equipped). Be sure to discharge the system before working on it. - Nick at Pelican Parts  
Troi Comments: My Boxster S '02 aircon is not blowing air when the engine is running, but does when the ignition is on the "ON" position. Any ideas what the problem might be due to? Thanks.
January 1, 2014
  Followup from the Pelican Staff: I would check if the blower is getting power and ground when the turned ON and the engine is running. If not, check the resistor and the switch. - Nick at Pelican Parts  
mikesz Comments: ok my reading is 100 any ideas why?
June 20, 2013
  Followup from the Pelican Staff: What reading are you referring to? - Nick at Pelican Parts  
Tania Comments: Can anybody tell me how much of the R134a do I have to refill my VW Caddy2,0 SDI Carrier NEOS 100, ASR 2006?
June 9, 2013
  Followup from the Pelican Staff: Sorry no, we do not have that information. - Nick at Pelican Parts  
Jana Comments: My citroen c2 aircon is working fine when it is cold but when it gets hot during the day the aircon doesn't want to work.
But when it gets cooler late in the afternoons the works again. We took it for gas to 2 different places but there is no problem with the gas. Can someone please help me?
November 13, 2012
  Followup from the Pelican Staff: We don't have your vehicle here in the US. But check that the electric condensor fan is working and the condensor is free from debris and not blocked. - Nick at Pelican Parts  
Jeff P Comments: MY 02 BOXSTERs hvac control blinks LO at me. I just had the a\c charged because of it. Is there a code that has to be cleared to erase the message?
August 2, 2012
  Followup from the Pelican Staff: Having an A/C service should set a fault code. I would scan the vehicle using a Porsche scan tool. Once you know the fault code you can adress the issue. - Nick at Pelican Parts  
Covekev Comments: Water condensation is Leaking into the passenger floor panel 2002 996c2. I assumed it is the ac drain but would like to know how to repair.
July 2, 2012
  Followup from the Pelican Staff: You can access the HVAC housing drain from inside the vehicle. I would bet just clearing it of debris should fix your problem. Remove the glove box or lower instrument panel trim. You'll see the drain attached by plastic tie strap. You can remove it an clear it. Be sure to route it properly when re-installing. - Nick at Pelican Parts  
JeffR Comments: I've just changed a leaking AC consenserand will also install a new desiccator. Do I need to evacuate the system before re gasing?

If so, what kit and procedure do I need as a DIYer?
April 5, 2012
  Followup from the Pelican Staff: It is best to evacuate the system with an A/C machine. This helps to remove moisture from the system. Putting in a vacuum also helps to see if there are any other leaks. This is best done with a professional A/C service machine. - Nick at Pelican Parts  
Bill Ryan Comments: If you just bleed off the R134, the old oil is still in the system. The only way to get the oil out is to flush the system. If your customers double the oil content, they run the risk of turning the compressor into a hydraulic pump........... and ruining it. They pump gases well, but not liquids! Most of your customers will think "completely empty" means no pressure.
February 28, 2012
  Followup from the Pelican Staff:
Thanks for the input on this one. We appreciate the help. I agree, it is best to evacuate the system to avoid over-filling the oil. It also removes moisture from the system while helping you confirm the system is sealed. - Nick at Pelican Parts
BrianW Comments: The low pressure a/c port on a 1999 996 are located up front under the hood. You'll need to remove the battery cover first. Then, using a Torx remove the cover on the passenger side. You'll see two 2 ports with black caps, it's the port with the green tape wrapped around the pipe.
September 24, 2011
  Followup from the Pelican Staff:
Thanks for the input on this one. We appreciate the help. - Nick at Pelican Parts
RichardS Comments: My 99 Carrera c4 has an evaporator leak, holds a charge for just about 2 weeks. Would it be feasible to go the air con sealant route? I live in hong kong and the shop has quoted me an astronomical figure to change the unit....
June 20, 2011
  Followup from the Pelican Staff: Sure, I do not see how that could hurt the system. - Wayne at Pelican Parts  
wm Comments: I'm interested in a manual but need one for an 07 Cayman. Do you have oe specially for the cayman or one that will work?
March 21, 2011
  Followup from the Pelican Staff: Unfortunately, with the modern cars, Porsche has discontinued manuals, and has instead put the information into their PIWIS system, which is only accessible by shops if you pay Porsche a ton of money. The good news is that people have hacked these systems and exported the "manuals" in PDF format. You can find them on eBay or the web. But, the quality of the manuals are not as good as the paper manuals of the past. - Wayne at Pelican Parts  
ChristianR Comments: Are the lines on my 1999 996 Carrera C2 just as accessible as the Boxster?
June 21, 2010
  Followup from the Pelican Staff: Yes, they should be in exactly the same spot if memory serves me properly. - Wayne at Pelican Parts  

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