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911 Nippondenso A/C Compressor Rebuild

Pelican Technical Article:

911 Nippondenso A/C Compressor Rebuild

Rod Walter


3-4 hours






Strap wrench, large pair of channel lock pliers, snap-ring pliers, deep metric socket set that certainly includes 10mm - 13mm sockets, 7/8-inch open-end wrench, 6mm hex key or socket, Phillips head screwdriver, flathead screwdriver, lots of shop rags or paper towels, 22mm wrench, workbench

Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 930 Turbo (1976-89)

Parts Required:

R-12 or R134a refrigerant oil, A/C compressor shaft seal kit, A/C compressor O-ring gasket kit

Performance Gain:

Your 911's A/C system will work better and cool your 911's cockpit more efficiently and effectively

Complementary Modification:

Have remaining Freon removed from the system by a professional A/C shop before beginning this project
Figure 1
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Figure 6
Figure 7
Figure 8
     OK, 911 air conditioning won’t ever remind you of being above the Arctic Circle. And because of its design, the system has a lot of places in which leaks can develop. One of the more common points for a refrigerant leak is at the shaft seal of the compressor. You may notice some oil on the compressor mount or on the underside of the decklid in a line from left to right above the compressor. Many folks decide to buy a new compressor to solve this problem. But if you’ve priced new or rebuilt A/C compressors you know that they can be quite expensive. However, with about $25 in parts, a three out of 10 skill level and 3 beers worth of time you can reseal your own compressor.

Tools you will need:

1.    A strap wrench or a large pair of channel lock pliers,
2.    A pair of snap-ring pliers,
3.    A set of deep metric sockets, especially 10mm, 11mm, 12mm, and 13mm,
4.    A 7/8” open-ended wrench,
5.    A 6mm hex key or socket,
6.    A phillips head screw driver, and
7.    A flat blade screw driver (for gentle prying).

Supplies and parts you will need:

1.    Lots of rags or paper towels,
2.    R-12 (Freon) or R134a compatible refrigerant oil (if you are using R134a make sure that the new oil is the same as what is already in the system),
3.    An compressor shaft seal kit, and
4.    A compressor o-ring gasket kit.

     The compressor that I rebuilt is a Nippondenso model 10P15C and the system is still using Freon (R-12) but make sure that you have the same compressor by looking at the model number on the small plate on the back of the compressor.

     I ordered both a shaft seal kit and a gasket set so that I would end up with a totally rebuilt compressor. You can, though, choose to replace only the shaft seal. The shaft seal kit has: 1) a new spring-loaded, carbon shaft seal, 2) a metal seal retaining ring/seat, 3) the o-ring for the seal seat/retainer, 4) a new circlip to hold the assembly in, and 5) new washers for the head bolts (these are the long bolts that hold the compressor sections together).

     The compressor gasket set contains mostly o-rings: 1) three large o-rings for resealing the case sections, 2) four small o-rings for resealing the suction and discharge fittings - where the shraeder (sp?) valves are located (you know, like the valves on a bicycle tire/inner tube), 3) one small o-ring for the shaft seal seat (a duplicate for the one in the shaft seal kit), and 4) five washers to use with the head bolts (again, duplicates for the ones in the shaft seal kit).

     Before beginning you should have any Freon that’s left removed from the system by an A/C shop - it shouldn’t cost much and with Freon at $50+ per lb. they should give you some sort of credit for when you have it refilled. Discharging Freon (R-12) into the atmosphere contributes to the destruction of the earth’s ozone layer and is prohibited by U.S. EPA regulations.

     Now you are ready for the rebuild. Begin by removing the compressor from the car and the clutch assembly from the compressor.

1.    Undo the two hoses from the compressor - the smaller fitting uses a 7/8” or 22mm wrench and the larger fitting uses a 1 and 1/16” or 27mm wrench but I carefully used a big pair of channel lock pliers since I didn’t have an open-ended wrench that large. Secure plastic wrap with rubber bands around the hose fitting ends to prevent system contamination. Don’t loose the o-rings on the hose fittings.  See Figure 1.

2.     Remove the three bolts that hold the compressor to its mounting plate, using a 13mm socket. Now you can tilt the compressor forward and take off the belt. Also disconnect the clutch wire.  See Figure 2.

3.     At the bench, kitchen table, or wherever (but probably not at the local tavern), remove the 12mm nut that is exposed at the nose of the compressor/clutch assembly. You need to hold the clutch drive plate in place to get the nut off or the assembly will just spin. This is the outermost piece of the clutch that has the rivets showing. It’s only about 3/8” or 1/2 “ thick and is separate from the pulley. Again, I carefully used a large pair of channel locks but the proper tool is a strap wrench. Once the nut and lock washer are off, the plate just pulls off. You can help it by carefully prying between the plate and the pulley assembly behind it. Watch for the spacers between the drive plate and the pulley and set them aside for reuse.  See Figure 3.

4.    The pulley is held in place with a 37 mm circlip. It doesn’t come with the kit so try to remove it carefully enough that you can reuse it unless you have a good local source for such things. I don’t. The pulley may be somewhat difficult to take off but you should not need anything like a gear puller. If you look inside the pulley’s shaft tube you can see the bearing that carries the pulley held in by a retaining spring. This may need to be replaced at some point. Mine did not require replacement.  See Figure 4.

5.     The ground for the clutch and a clip for the clutch wire are attached to the compressor by a phillips head screw. Remove it now. I had to slot the screw head with a Dremel tool and use a large flat-bladed screw driver because the screw was too tight.

6.     The magnetic coil is held on with a 46mm or so circlip. Remove it and, again, set it aside for reuse if possible. Pull the coil off. Notice that there is a locating pin on the compressor that mates with a hole in the coil for reinstallation. My coil had three holes but only one is in the right place.

7.    Take the woodruff key from the compressor shaft and set it aside so that you don’t lose it.

     Now for the actual compressor stuff. The compressor consists of four sections: two end caps and two thicker middle sections with the pistons, cylinders and wobble plate (on the compressor shaft).

1.     Remove the five compressor head bolts using a 6mm hex socket or key. Each has a washer and you can discard them since you have new ones from either kit.

2.     If you are going to reseal the compressor take off the suction and discharge fittings, noting their placement. They will go on the wrong way (ask me how I know) and if you do happen to get them on wrong during reassembly just remove and switch them. Don’t remove these if you are not going to reseal the case.

3.    Once the head bolts and the suction and discharge fittings are removed the case sections will just split apart under hand pressure. To replace the shaft seal only, pull off just the front section of the compressor. You will be able to see the tops of the compressor pistons and one of the large o-rings for the case.  See Figure 5.

4.    The front piece of the compressor with the “nose” is where the shaft seal is located. Look inside the nose, find the felt seal and its brass retainer and remove them. They are to be reused.

5.    Remove the circlip from inside the nose. You do have a replacement for this so don’t worry about ruining it.  See Figure 6.

6.    From the inside (compressor side) of the nose drive out the seal and its retaining ring with a 10mm or 11mm deep socket and a hammer. Go carefully so that the seal and ring don’t “cock” in the housing. You will destroy the old seal - when you see pieces of carbon don’t worry about it. The retaining ring is held in place with a friction fit using an o-ring. It may help you to remove the seal if you lubricate the nose with some of your refrigerant oil. The seal itself sits loosely inside the shaft housing (nose); it’s not pressed against the sides.

7.    Once the seal is out, clean the shaft housing so that you don’t have bits of carbon in there.  See Figure 7.

8.    Install the new seal. The spring-loaded carbon assembly drops in first, the carbon facing out and the spring toward the rest of the compressor. You should avoid touching the carbon itself. Now, you may notice that the retaining ring is different than the one you removed. One side of the new ring has a flat surface - put the retainer in with this flat surface facing the carbon seal after lubricating the new o-ring with refrigerant oil. Now here I made a judgement call. The new retainer will not take up the whole space between the seal and the circlip that you removed . I drove the retainer (with a 13mm deep socket) to a point just below the groove for the circlip. If you study the assembly, the actual seal is formed by the carbon piece pressed against the retainer’s flat surface and the circlip just prevents the pieces from working their way out along the shaft. When you place the compressor nose back on the compressor the seal will be spring loaded against the retainer creating the seal. I suppose that you could drive the retainer all the way to the seal but I chose not to.

9.    Install the new circlip in its groove.

10.    Allow as much of the old refrigerant oil to drip out of the compressor as you can and put 2 oz. of new oil in the compressor. Where you add it doesn’t matter - it just circulates throughout and is carried by the refrigerant around the system.

11.    If you are not resealing the case you are finished and can begin reassembly. When replacing the compressor nose piece be careful to avoid nicking the carbon - just put the shaft through the seal as straight as you can.

12.    If you do reseal the case simply separate the sections, replace the large o-rings and put it back together. All of the components are constructed in such a way that proper reassembly is made obvious with pin locations and non-symmetrical parts. Also replace the four o-rings at the hose fittings. Hint: separate the two large case sections, replace that o-ring (lubricate with refrigerant oil), replace the four hose fitting o-rings, put the fittings back on and only then remove the rearmost case section to replace its o-ring. This will make sure that the pistons and wobble plate don’t wander out of the compressor while you are working. They are a royal PITA to put back together.  See Figure 8.

13.    Using the new washers, reinstall the five compressor head bolts. If not yet reinstalled, replace the hose fittings.

14.    Replace the clutch assembly. Make certain that you reinstall the spacers between the pulley and the clutch drive plate.

15.    Remount the compressor, hook up the clutch wire and reattach the hoses, lubricating (and replacing, if necessary) the hose o-rings.

16.    Take the car to an A/C shop and have it refilled. To be secure and happy you may want the technician to put a leak detector near the compressor shaft to check your work.

17.    You’re done!

If you use this article to rebuild your compressor and find that I’ve forgotten something or have been unclear, please e-mail me with feedback. Good luck!

Rod Walter
PCA Lincoln Trail Region

Comments and Suggestions:
Karozza Comments: I would like to do this procedure on my 1989 944 S2 compressor which is also a nippondenso; how successful are these re-builds & how long do they last? Being overseas,do you have an e-mail contact so I may order the seal/o ring kit?
June 16, 2017
  Followup from the Pelican Staff: If the mechanical parts are OK, and the rebuild goes well, should last as long as a new one. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
bunk Comments: I have 1991 renault 2.2 engine that needs a/c compressor rebuilt.Can you do?
December 19, 2013
  Followup from the Pelican Staff: We don't rebuild compressors. But we might be able to locate one or send it out for you. Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts  
robert Comments: re-Jack posting June 30/13 on his 88 same as mine there is this company in Texas,I since lost its name ,they sell new replacement kit for the Porsche & Jag about $2000 w/wo compressor.the photo showed it resembled to my rear tail AC unit kit.
November 14, 2013
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
diva_3181377 Comments: My AC compressor is weak. The high side does not go above 250-260 with 55 on low side with proper amount of refrigerant at 95F. Can this be rebuild or needs replacement. It cools ok as long as it is 100F outside. New expansion valve and no leak in the system.
August 30, 2013
  Followup from the Pelican Staff: Personally, I would replace it. This way you know it is right from the get go. Give our parts specialists a call at 1-888-280-7799. They can help you find the right compressor. - Nick at Pelican Parts  
abutalib Comments:
July 28, 2013
Jack Comments: Ok I'm ready to try rebuilding the compressor on my 88 but I'm not seeing a rebuild kit for sale.
Little help!

June 30, 2013
  Followup from the Pelican Staff: If there's no rebuild kit, you will have to replace it. Give our parts specialists a call at 1-888-280-7799. They can help you find the right parts.
- Nick at Pelican Parts
Kuehl Comments: Justin,
Once you have the compressor re-installed, with new o-rings for the hose and component connections, a new drier,...
you will need to add refrigerant oil. For a compressor and drier R&R 5 fluid ounces is safe. If the system was running R12 we suggest using Ester refrigerant oil as it is compatible with residual mineral oil and works with R12 and R134a refrigerants. If the vehicle was converted previously to R134a and PAG was used, continue with PAG.
You can either add the 5 ounces directly into the compressor prior to bolting it on or have your ac technician inject the oil.

Then the system is evacuated, charged and tested.

April 16, 2013
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
carlosmiami1 Comments: Hello guys! Does anyone know where I can get the suction and discharge fittings, for the Nippon Denso compressor, exactly as illustrated here on your figure 2. overview, for a 1988 911 Porsche? I purchased a new Denso Compressor 471-0124, but they do not come with the suction or discharge fittings. If any one could help me that would be super! New or used would be fine! please contact me at
Thanks Guys,
February 12, 2013
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
Mori Comments: What type of oil should I use in a Nippondenso auto a/c compressor Model 10P15C That I rebuilt used on a toyota supra GTS 1982.
October 1, 2012
  Followup from the Pelican Staff: This will depend on the refrigerant you currently have in your vehicle. I would imagine at this point it is R134, which would be a PAG oil. - Nick at Pelican Parts  
Abdullah Comments: At the beginning, I thank you so much for your post.
It is very clear, understandable and very well-arranged, I did rebuild one before but from your post, I got extra valuable information that I accidental missed.
I have a question here, what is the torque force value for the five compressor head bolts? Thanks again.

Best regards
July 15, 2012
  Followup from the Pelican Staff: 18 Nm (14 ft-lb) - Nick at Pelican Parts  
max Comments: i have a 1992 nissan sentre 1.6 lt I cant get suction tube to seal at the compressor. i have used several o rings an pressure tested it several times. I cant get the simple fitting to seal. Is there a special way to it together
May 12, 2012
  Followup from the Pelican Staff: I would replace the line. Other than checking with re-builders for the parts I am not sure of any other option. - Nick at Pelican Parts  
brucen Comments: Is this compressor the same as on a 91 944 S2? The pulley is different but is otherwise the same?
August 15, 2011
  Followup from the Pelican Staff: I am not sure. What is the part number of your compressor and the one you want to replace it with? I might be able to cross reference them. - Nick at Pelican Parts  
oneshinyman Comments: where can one find compressor parts and gaskets to do a rebuild.
July 16, 2011
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right parts.
- Nick at Pelican Parts
Steve Comments: Is Fig 3 and Fig 4 the same or am I missing something?
July 1, 2011
  Followup from the Pelican Staff: They do look the same to me. I will look into it. Thanks for catching that. - Nick at Pelican Parts  
Michael Comments: Hello, I have a lamborghini gallardo, My car recently stop running cold. I remove the condenser to see if it had any freon but it was empty. I pumped freon back in my car. but it only allow a little freon in the system. I kept the AC on high for the compressor to pump. but I the car only took a little freonnot even half a bottle. I checked to see if freon was in the ac with a nail pushing into the pressure line. Freon came out. but my car is still not running cool. Do you think its my AC compressor?
April 22, 2011
  Followup from the Pelican Staff: Sounds like you overcharged it. I would have the system evacuated and checked for leaks. Then recharged and check system pressure. - Nick at Pelican Parts  
Max Comments: Hi,

If I have flushed my system No oil in any parts, is it ok to add the full 8oz to the compressor itself, or can that lock it up somehow? Or is it no problem.
November 17, 2010
  Followup from the Pelican Staff: Adding the oil to the system shouldn't be an issue if there is no oil in there right now. - Wayne at Pelican Parts  
Chris Comments: I have the problem that the shaft seal is leaking and I tried to find where i can buy the seal kit, but i found it nowhere. Can anybody tell me where i can buy it.
September 10, 2010
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
JNico'85 Targa Comments: Was the oil PAC 100 used when rebuilding the compressor?
July 26, 2010
  Followup from the Pelican Staff: If using R134, you'll want to use a PAG oil. - Nick at Pelican Parts  
timj Comments: I have a small leak in my compressor and I tried to go the cheap and easy route and attempted to fix with a product called quest superseal and of course it didn't work so I know the nice ice cold air is going to be short lived if I take my compressor off to rebuild it is all that sealant going to clog up the other hardware in my ac system of course ending up in completly replacing my entire ac system or should I be ok and go ahead and take compressor off repair it and reinstall
July 16, 2010
  Followup from the Pelican Staff: I'm not sure - if the product is certified to use on A/C systems, then when you evacuate the system, it should come out with the old refridgerant. - Wayne at Pelican Parts  
six points Comments: how can I find out why the compressor does not energize when I turn on the AC switch
June 20, 2010
  Followup from the Pelican Staff: It could be a problem with the A/C controller / computer, or it could be that there is not enough fluid in the system to trigger the pressure switch. The switch turns off the compressor if the pressure in the system is too low (i.e. no fluid in the system). The switch might be defective / stuck too. - Wayne at Pelican Parts  
June 2, 2010
  Followup from the Pelican Staff: My sources seem to indicate 2 ounces in the compressor. - Wayne at Pelican Parts  
May 26, 2010
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799 and they can help figure out your ac compressor oil needs. - Nick at Pelican Parts  
mb mechanic. Comments: i need rebilt kit for nippondenso compress for mencedes bens s
140 1996 can you raccomend or know a place were to by it thank you f. from nj.
May 8, 2010
  Followup from the Pelican Staff: I don't think they sell these separately. They typically want you to purchase a factory rebuilt compressor only. - Wayne at Pelican Parts  
Wins Comments: the parts are available to rebuild the Nippondenso unit. The shaft seal kit and gasket set with O rings are sold separately, for $14 and $18. Together they cost less money than the shaft seal kit sold by the another Porsche parts site the "Z" parts guys. Make sure you identify the model of your specific compressor.
September 10, 2009
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
Garth Comments: I purchased a compressor shaft seal and am going to attempt to replace it. They may also have the compressor body seals
July 9, 2009
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
57chevy Comments: Wayne
I have searched the web but I cant find a place that sells the rebuild parts for automotive compressors. Where can I find the parts to rebuild them??
June 18, 2009
  Followup from the Pelican Staff: I don't think they are available separately - the compressor companies want you to purchase one of their fully rebuilt units for more $$$. - Wayne at Pelican Parts  
john Comments: i want to rebuild my 1988/944 ac compressor....can you give me a parts list with price, thanks
June 15, 2009
  Followup from the Pelican Staff: 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  
justin Comments: once you have put the compresser back on and tighten everthing do you have to have the air vacumed out
April 29, 2009
  Followup from the Pelican Staff: There is a specific procedure for evacuating empty A/C systems. Yes, you need to pull a vacuum on it, and you should also replace the receiver/drier if it's been exposed to air (moisture). Unfortunately, most people don't have the equipment to do this task in their own garages, so I recommend taking it to an expert at that point for evacuating and refilling. - Wayne at Pelican Parts  

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Page last updated: Tue 2/20/2018 02:17:45 AM