| OK, 911 air conditioning wont 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 youve 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
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 thats left
removed from the system by an A/C shop - it shouldnt 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
earths 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 didnt have an
open-ended wrench that large. Secure plastic wrap with rubber bands around the hose
fitting ends to prevent system contamination. Dont 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. Its only about 3/8 or ½ 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 doesnt
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 dont. The pulley may be somewhat
difficult to take off but you should not need anything like a gear puller. If you look
inside the pulleys 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 dont 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
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. Dont 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 dont 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 dont cock in the housing. You will destroy the old
seal - when you see pieces of carbon dont 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); its not pressed against the sides.
7. Once the seal is out, clean the shaft housing so that you
dont 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
retainers 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
doesnt 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 dont
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. Youre done!
If you use this article to rebuild your compressor and find that Ive forgotten
something or have been unclear, please e-mail me with feedback. Good luck!
PCA Lincoln Trail Region