Jaguar XJ-S. Manual - part 126

 
 

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the rubber isolator and at the other end to the clutch face plate itself.  These three straps can flex to allow the face plate 
to move forward and aft fairly freely, but they’re springy and tend to pull it forward away from the pulley.  The 
magnetism pulls this face plate against the front surface of the pulley, engaging the drive.  This is a steel-against-steel 
friction drive. 

The clutch is serviceable separately from the compressor.  A replacement clutch can be purchased from local auto parts 
stores, and the old clutch removed and the replacement installed.  This does not involve disturbing the freon circuit. 

A replacement clutch may include the drive plate, the pulley, and the coil, or it may include just the first two items; if 
you need a coil, you should ask.  Note that the A-6 compressor has been used on lots of different automobiles (not to 
mention road graders, agricultural machines, you name it) but there were several different pulley arrangements 
involved.  Since the replacement clutch includes the pulley, you’ll need to find the correct type.  It’s still very common, 
since it was used on several GM cars; the computer terminals in the auto parts store should bring up the correct item. 

You can buy a new clutch, or you can buy a “rebuilt” clutch.  A clutch having been rebuilt should mean at least four 
things:  First, the steel-against-steel friction surfaces on the drive plate and the pulley have been machined to render 
them flat and new-looking again.  Second, the rubber in the drive plate has been replaced; the rubber is bonded to the 
hub of the drive plate on one side and to a flat steel disk on the other, much the way a motor mount is made.  Third, the 
pulley should have a new bearing in it.  Finally, if it comes with a new coil, presumably that has new windings inside. 

Why am I telling you all this?  Because apparently you need to know.  A properly rebuilt clutch costs as much as some 
of the rebuilt compressors discussed above.  When buying a rebuilt compressor, you apparently can get any of at least 
four different treatments of the clutch on that compressor.  One option is that you can buy a rebuilt compressor without 
a clutch, apparently so you can install your own.  This is probably for mechanics who want to make sure the clutch is 
good and installed properly; it’s not likely anyone would opt to reuse their old clutch with a compressor replacement.  
Second, you can get a rebuilt compressor with a rebuilt clutch.  Third, you can get a rebuilt compressor with a new 
clutch.  And, finally, believe it or not, you can get a rebuilt compressor with a non-rebuilt clutch! 

Yes, that last option is totally unacceptable.  You can easily tell what’s up with the rebuilt compressor someone is trying 
to foist upon you.  First off, you can look carefully into the gap between the plate and the pulley and see if the surfaces 
appear to be freshly machined.  Second, you can look at the layer of rubber built into the drive plate.  It’ll be coated 
with new black paint, but don’t let that fool you.  If it’s new, the rubber will be a neat shape with clean edges.  If it’s an 
old part with fresh paint, the rubber may be distorted, bulging on the sides, maybe even cracked.  Send that compressor 
back, and don’t consider any other compressors from that rebuilder. 

The incidence of rebuilt compressors with non-rebuilt clutches may explain a couple of the other options available.  
Getting a compressor without a clutch enables the mechanic to install one himself, so he knows what parts were going 
in.  Getting a rebuilt compressor with a new clutch is perhaps a response to mechanics getting rebuilt compressors and 
having the clutches fail shortly thereafter; it’s possible that a rebuilt clutch would have been just as good, but they 
didn’t realize the clutch on the compressor they were installing had not been rebuilt, so they conclude that a rebuilt 
clutch is unacceptable. 

Of course, it’s also possible that rebuilt clutches are unacceptable -- or, more likely, some rebuilt clutches are 
unacceptable; perhaps some rebuilders don’t bond rubber to metal well or use weak rubber or some such. 

 

BELT WIDTH:  Automotive V-belts are commonly available in two different widths.  The narrower belts, often used 
on alternators and the like, are about 10mm wide and the edges of the matching grooves will be 10mm apart.  The 
wider belt, typically used to drive A/C compressors and other heavy loads, is 13mm wide.  In modern parlance, the part 
number of a 10mm belt will usually have a 15 in it somewhere, while a 13mm belt will have a 17.  I hope that makes 
perfect sense to you. 

The other three digits are the length in tenths of an inch.  So, a 58-1/2” belt 10mm wide is a 58515 from some makers, a 
15585 from others.  A 58517 or 17585 is the same length but a 13mm belt. 

 
 

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If you’re fiddling around with accessory drives, the crank pulley on the XJ-S has grooves designed to work with either 
width belt.  A 10mm belt will sit deeper in the groove, so the crank pulley effectively becomes a smaller diameter 
pulley -- moving the 10mm belt slower than a 13mm belt would move in the same groove. 

 

COMPRESSOR CLUTCH REMOVAL AND REFIT:  The SIII XJ6 ROM includes instructions on replacing the 
clutch and so does the 4-volume XJ-S Service Manual.  However, the author’s XJ-S ROM does not and neither does 
the Haynes.  Since these are the manuals most owners are likely to be relying upon, instructions are provided here.  Of 
course, these are presented differently than those in the Service Manual. 

A warning, though: this is commonly regarded as a difficult task with considerable risk of failure.  There are many 
people with experience at this job thanks to this being a GM product, and you might be wise to seek out such an 
experienced person rather than try this yourself. 

First off, the Service Manual says you need to discharge the freon and remove the compressor to the bench.  False -- 
although you may need to unbolt the compressor from the engine to move it around a little. 

To R&R the clutch you will need two special tools: a puller to get the drive plate off, and an installer to put it back on.  
Four Seasons and Factory Air both offer such tools with numbers 59509 (puller) and 59502 (installer), while Discount 
Auto Parts offers Cool-Aid! tools 34460 (puller) and 34461 (installer).  The tools are around twenty bucks each; the 
installer is a bit more expensive since it includes a ball bearing.  Both tools are also commonly included in collections 
of automotive air conditioning tools, some of which use a couple of generic tools with lots of different attachments to 
adapt to various types of compressor. 

Some auto parts stores will rent or loan these tools to you for free.  Or, maybe not.  AutoZone includes the puller in its 
collection of rental tools, but not the installer.  They refer to the puller as their rental tool number 27002. 

If you don’t have the puller, it might help to know that the internal threads the puller screws into are 7/8” x 14 TPI, 
which is the same as a 1/2” NPT except for the taper.  Hence, you can screw a piece of pipe into this hole.  If the pipe 
hits bottom before the tapered threads tighten up, cut a bit off the end of the threads.  At this point, you may be tempted 
to attach a slide hammer or other apparatus for yanking, but note that the Service Manual includes warnings that 
applying loads to the shaft can cause damage inside the compressor.  The thing to do would be to screw a fitting of 
some sort into the hole and thread a bolt through the center of that fitting to make a tool that works just like the official 
tool, pushing the shaft out the center of the drive plate. 

If you don’t have the installation tool, you can use an internally-threaded sleeve and a threaded rod or stud to extend the 
threaded end of the shaft and use a nut and some washers to pull the drive plate on.  The challenge is finding a sleeve 
with an internal thread of 3/8” x 24 TPI and an OD less than 1/2”.  Good luck!  You might find a long nut or coupling 
nut, but you’ll probably need to grind the points off the external hex to get it to fit.  Another idea might be to get a small 
piece of tiny pipe or sleeve and use a tap to thread the inside. 

Incredibly, there’s actually a plausible solution here.  Discount Auto Parts sells a package of two “Shock Stud 
Extenders”, Superior no. 13-6501, for about four bucks.  These things are intended to screw onto the top stud on a 
shock absorber for rednecks doing heinous things with the ground clearance on their pickup trucks, but the threads are 
correct for our purposes.  They have an external hex that will have to be ground down, but that wouldn’t be too 
difficult.  You get two tries, too. 

You will also need snap ring pliers -- big ones. 

First you need to remove the nut that’s down in the hole in the center front of the drive plate.  It may be a 9/16” hex, but 
on the author’s car it was a 14mm hex.  The socket used doesn’t need to be a special thinwall model, but it can’t be a 
big bulky thing or it won’t fit in the hole.  The nut is regular right-hand thread, 3/8” x 24 TPI (NF). 

Next you need to use the puller.  If you’re lucky, the puller you have will fit between the compressor and the radiator 
upper rail.  If not, you’ll need to unbolt the compressor to tilt the nose up to work on it.  That’s not too difficult to do, 
and it gives you better access to what you’re doing anyway. 

 
 

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Once the drive plate is off, a large and obvious external snap ring must be removed to allow the pulley and bearing to 
come off.  The bearing is not a very tight fit on the compressor, so once the snap ring is off it shouldn’t be too difficult 
to remove.  Perhaps a few taps with a plastic mallet or a hammer and wooden drift will help. 

The replacement clutch should come with a new bearing already in place in the replacement pulley, but if you need to 
get at it for some reason: the bearing is pressed into the pulley from the front and is held in the pulley with a barely-
noticeable wire snap ring.  Walter Acker IV says “The bearing number should be an A/C delco 15-2802.” 

Once the pulley is off, another large external snap ring must be removed to get the coil off. 

It appears that the replacement coil could be installed with the terminals facing several different directions, so make 
sure they point where you need them to. 

Before installing one of these large snap rings, look closely at it.  The flat side of the snap ring needs to go against the 
part being held in place.  The other side has a bevel around the ID, and this bevel not only makes the snap ring easier to 
install but also helps it hold the part snugly.  After installing, tapping around the circumference of the snap ring to make 
sure it’s fully in couldn’t hurt. 

If installing the replacement pulley requires tapping, do not tap on the flat friction face; the wire snap ring holding the 
bearing in the pulley may not appreciate it, and neither will the bearing itself.  You need to tap directly on the inner race 
of the bearing, which means you need to have a sleeve with a 1-5/8” ID to use as a drift.  A PVC pipe fitting worked 
well for me. 

The key that goes on the compressor shaft is square, 4mm on a side.  It’s also bent.  No, it isn’t damaged; the Service 
Manual says that it is deliberately bent to hold it in its groove during assembly. 

Before reinstalling the drive plate, you need to put the key in place.  The Service Manual says to fit the key into the 
drive plate, and then line it up with the keyway in the shaft during assembly.  Unfortunately, if the key is installed in the 
drive plate it will interfere with the installer tool.  The key must be positioned in the keyway on the compressor shaft.  
And if you do that, the key will probably fall out while you’re trying to install the drive plate.  It appears that the most 
reliable method is to position the key in the drive plate but as close to the back end as possible.  Put the drive plate onto 
the shaft, lining up the key, and use the installer tool (threaded onto the shaft as far as possible before it hits the key) to 
pull the drive plate on just a little.  Then remove the installer tool and use a hammer and a nail to drive the key back into 
the groove on the shaft until the end is flush or below the shoulder on the shaft.  Then screw the installer back on, being 
able to thread it all the way down this time, and continue pulling the drive plate into place.  The instructions in the 
Service Manual say you’re supposed to install the tool, push the drive plate on a little, take the tool off, check the key to 
make sure it’s in place, then reinstall the tool and push the drive plate the rest of the way on; perhaps they were 
inferring that you should be driving that key into its proper position. 

The thrust bearing that comes on the Cool-Aid installer tool is a real cheap POS and may not survive the first drive 
plate installation.  Here’s my suggestion: the first time you put the tool on, omit the bearing and use a 5/8” flat washer 
instead.  After you remove the tool to drive home the key, put the tool back on with the bearing and the flat washer -- 
perhaps even two flat washers if you’ve got room, one on each side of the bearing.  This will prevent the housing of the 
cheap thrust bearing getting crunched and allowing the drive plate to get cocked during installation.  Hold the washers 
centered until the tool snugs up to hold them in place; if allowed to lay against the threads, they will scrape the threads 
as the tool is used. 

Of course, you could simply provide a good thrust bearing. 

As mentioned above, applying axial force to the shaft is verboten.  Standing the entire compressor in your press to push 
the drive plate on is not recommended. 

The instructions in the Service Manual indicate you’re supposed to use the installation tool to push the drive plate on 
just until the gap between the friction faces is 3/32” or so, then remove the installation tool.  The drive plate is pushed 
the rest of the way into position with the nut.  Forget that; use the installation tool to position the drive plate exactly 
where you want it to end up.  Don’t rely on the nut moving the drive plate on the shaft at all.  Even if it would (which it 
won’t -- see below), turning the nut against the front surface of the hub galls it up and may prevent it going on as far as 
it needs to.  There’s a reason the installation tool includes a ball bearing. 

 
 

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According to the Service Manual, the desired gap between the friction surfaces is 0.56-1.45mm (.022”-.057”) -- but 
really, the objective is as small a gap as you can muster without the surfaces contacting when the clutch is disengaged.  
If you close down the gap too much and the pulley starts dragging, use the puller tool to back it off a bit.  In fact, that’s 
really not a bad installation procedure:  Install it too far until the pulley drags, and then install the puller and pull just 
until it spins freely. 

The Service Manual says to install the nut narrow boss end first and tighten it down to 15 ft-lb.  If you do this, the nut 
won’t get within 1/8” of an inch of touching the drive plate.  The diameter of the narrow boss end of the nut is small 
enough for the center hub of the drive plate to pass right over it, and only the tiniest portions of the points on the nut 
hex could actually contact it.  Since the narrow end of the nut will contact the shoulder on the shaft and won’t go any 
farther, the nut will be stopped long before the points get near the drive plate.  The only plausible objectives would be 
to “catch” the drive plate if it decides to slide off -- which it won’t -- or to prevent the key from sliding out. 

If you’d like the nut to actually help hold the drive plate in place, look carefully at the shoulder of the shaft after the 
drive plate has been positioned properly with the installation tool.  If the shoulder on the shaft is within the hub itself, 
put a flat washer on the shaft.  This washer needs to have a 3/8” ID and a 3/4” OD.  Then screw the nut on flat side first. 
 Tighten it down until it gets snug, indicating it has pushed the washer against the hub, and quit.  Don’t even think 
about tightening it enough that it might move the drive plate and close up the gap. 

If the shoulder of the shaft is protruding from the center of the hub, you’d need to provide a sleeve that sits inside the 
opening on the front of the drive plate and has an ID of at least 1/2” to fit around the shaft.  You might cut a ring from a 
piece of 5/8” copper pipe.  You’ll probably need to cut a notch in this sleeve to fit around the key unless you shortened 
the key before you started -- which isn’t a bad idea; the key being a little shorter won’t hurt anything.  Install this 
sleeve, then the flat washer described above, then the nut flat side first and tighten gently as described above. 

You could reasonably opt to forget all that and just thread the nut on as the Service Manual says -- or even just leave it 
off.  The retention that matters here is the press fit.  The pulley on the water pump is held only by a press fit, the 
impeller in the water pump is held only by a press fit, the hub holding the fan clutch is held only by a press fit, clearly if 
a press fit isn’t reliable we’re in big trouble. 

 

FRONT SEAL REPLACEMENT:  The Service Manual provides instructions for replacing the front seal on the A-6 
without disassembling the compressor.  The first step is to remove the drive plate of the clutch as described above.  The 
rest of the procedure involves several special tools.  It’s doubtful that this would ever be a worthwhile undertaking, 
since fiddling with that seal requires discharging the freon circuit -- at which point you might as well just slap in a 
rebuilt compressor. 

 

COMPRESSOR PROTECTION CIRCUIT:  Just below the inlet and outlet connections on the A-6 compressor is a 
sensor held in place with a C-clip, with a wire connected to it.  On the 1983 XJ-S, this is a thermally-operated switch 
that shorts to ground in the event that there is trouble with the freon system.  The shorting causes a resistor within a 
three-connector fuse assembly to heat up, which in turn causes a fuse to melt, breaking power to the clutch and 
disengaging the compressor.  This is a common arrangement on GM vehicles, and the fuse assembly is readily 
available; Victor part number V-909, “GM Thermal Limiter”, is one common replacement.  The fuse is usually attached 
to a mounting hole on the compressor itself. 

Do not connect the fuse backwards.  There is a little tang on the center connector that is intended to indicate which way 
the plug goes, but it’s not very foolproof.  If you install it backwards, the clutch will not engage and the fuse will blow 
immediately. 

A replacement compressor is likely to have an aluminum blank-off plug in place of the fault sensor.  It is probable that 
you cannot install the thermal type sensor in place of the plug because there has to be a suitable opening underneath the 
plug for the tip of the sensor, and there often isn’t.  However, the sensor wire can just be left disconnected and the 
system will work fine -- there just won’t be any protection for the compressor if the system loses freon.  In fact, it is just 
as well to remove the fuse assembly as well and run the power wire directly to the compressor clutch.  Since the 
standard procedure is to replace the compressor in the event of freon loss anyway, this may be acceptable.