Jaguar XJ-S. Manual - part 153

 
 

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windows.  This went away (all switches wired in parallel) with the SIII.  I’m not sure exactly when the S changed over, 
but it was certainly by the time the H.E. was introduced.” 

If you have an early car and are having trouble with this system or these switches, the ideal solution might be to simply 
install the window control relay scheme described above and delete that daisy-chain nonsense.  If your original 
switches can be made to work at all, they can be wired to operate the relays, and you will no longer be limited to one 
window at a time.  Since you would be providing new and substantial power wiring to the window motors, there’s no 
risk of overloading any existing wiring. 

 

PRE-88 GEARS:  Replacement gears are available separately.  The motor/regulator assembly consists of a motor with a 
worm gear built into the output shaft, a housing that holds a gear/coupling assembly, and an arm with a gear rack.  If 
your problems happen to involve that gear/coupling assembly, you’re in luck!  Chuck Sparks found out that the part is 
available in auto parts stores.  It’s called a “window lift gear kit”, and it’s made by Pronto, part number 42-90.  It is 
described as applying to “any GM window regulator using a 46-spline, 12-tooth gear”.  It is described as fitting GM 
electric windows in cars and trucks from 1956-80. 

There are no splines involved; there are two gears, a metal 12-tooth gear that engages the arm and a plastic 46-tooth 
gear that the worm gear drives.  In between the two gears is a coupling assembly with a rather massive spring in it.  All 
mounted on a short shaft.  It’s this entire assembly, both gears and the coupling mounted on the shaft, that comes in this 
kit.  Cost is about $20. 

A real cinch to install, too -- once you get the regulator out of the car.  It’s obvious, just take a cover off the housing, 
remove the old gear, install the new, reassemble. 

 

PRE-88 WINDOW MOTOR REPLACEMENT:  They are Delco, so you can get them from a Chevy in any junkyard 
in America, right?  Apparently not.  The window motors in the XJ-S are made by “Delco of England” and seem to be a 
little different than generic GM stuff. 

Still possible, though.  Don Lawton:  “My Jag had the cylindrical Delco motors.  I found that I was able to replace the 
motor/gearbox assembly with a Delco module off GM/Oldsmobile cars from around the mid-1980's.  The unit is not the 
same as the Jag one, but the pinion has the same gear size; i.e. it fits the jag regulator sprocket.  The unit also has a 
slightly different bolt mounting pattern, but a few minutes of work with a round file on the regulator plate enabled it to 
fit just fine. 

“Another good point is that the passenger side GM regulator motor fits the driver's side on the Jag; i.e. you can get one 
that is less used and in good shape.  The GM unit is slightly longer than the Jag so it sticks up a bit higher in the door, 
but tucks in nicely behind the mirror switches. 

“I picked up several good GM regulator units from a local 'dig-it-out-yourself' auto wrecker for CDN $10 each, so I 
anticipate unstuck windows for the remaining life of my car!!” 

Since the indications are that GM changed their window motor design in 1981 and Jaguar followed suit in 1988, it’s 
entirely possible that a junkyard window motor from a pre-81 GM car would fit the pre-88 Jaguar even better -- maybe 
with no modifications at all.  On the other hand, perhaps it’s a good idea to upgrade to the later style motor. 

 

1988-89 ELECTRIC WINDOW MOTOR FAILURES:  On the ‘88-89 Delco units, the housing on the motor itself gets 
loose and jams the rotor, or lets water in.  Victor Naumann says, “I have replaced a lot of motors that the back has fallen 
off of and water has ruined.” 

Steven Draper reports, “After taking the door apart, I noticed that the case on top of the window motor that holds the 
magnets is held on by only two bolts.  The rear bolt had slipped some, and could not be tightened completely because 
of the soft metal.  The bit of play between that casing with the magnets and the internals of the motor that spin about 
was enough to cause the motor to only work when you beat the side of the door.  I inserted a slightly larger bolt with a 
nut on the bottom.  I was able to put the new bolt in without taking the motor out.  Believe it or not, the window now 

 
 

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rockets up and down.  If you've got a window that doesn't want to go up and down and tapping on the door helps, this 
could be your problem.”  If you can’t find a suitable long bolt, consider threaded rod with a nut at both ends. 

“It was interesting because the case had four bolt holes but the motor part with all the gears in it only had two holes for 
the case to attach to.”  It might not be a bad idea to put some aluminum tape or silicone sealant over the unused holes to 
keep water out. 

“BTW, on the Delco motor, if you put the stator on reversed from how you took it off, the motor does the opposite of 
what the switch intends.”  Actually, this is probably true on any window motor.  Might be a good idea to mark which 
way the case goes before disassembly, although you could conceivably just turn the switch around in the console. 

 

1988-89 ELECTRIC WINDOW MOTOR REPLACEMENT:  Peter Cohen reports, “'88's & '89's are known to have 
problems with the window motors.  I have an '89 XJ-S and have replaced both window motors with the new style 
Bosch motors.  I highly recommend them.  The windows just zip up and down like they never did with the Delco 
motors.  If you have an extended warranty, this should be a no brainer -- make them buy you the new motors.  If the 
warranty company won't come through, sue their no good ass in small claims court. 

“Some other insights into the window motor upgrade: 

“1. When this upgrade first came out, it was only sold as a complete motor/regulator assembly.  It is now available as 
two separate parts. 

“2. When I bought my left side assembly a few years ago (about $325 then), two of the holes on the motor seemed not 
to line up with the holes in the black sheet metal panel in the door, & I had to drill new ones.  This was not a problem 
with the right side, separate motor & regulator assembly which I bought in April, but I did have another problem: Both 
the regulator and motor shipped to me as right side were actually left side.  The regulator assembly was in a sealed 
Jaguar package with the correct Jaguar part number for the right side.  I took this to the local Jaguar dealer who 
cheerfully swapped it for a left side regulator, without my asking, and without asking where I got it.  Being so 
successful with the regulator, I took the motor to another Jag dealer.  Now, here's where it gets interesting.  The motor 
came in a Bosch box, so I was a little nervous about trying to swap it at a dealer.  I brought in the motor without the 
box, and again, the dealer swapped it without my asking.  However, the number on the motor was different enough 
from the one I brought in that it wasn't just the difference between left and right.  Also, the motor from Jaguar comes 
with 3 torx screws, and while the Bosch unit had no external wiring at all (just tabs to connect the wires), the Jaguar 
issue not only has the wires, but they are potted onto the motor.  This leads me to believe that there is a standard issue 
Bosch motor that we can buy and adapt, even if Bosch won't sell the Jaguar number. 

“3. There is a different type of plug on the Bosch motor (although still only 2 wire).  You can cut & splice your old 
wires, or Jaguar sells a clean little adapter assembly to do it right.  I have done it both ways, and both work.  The 
adapter is $40, so you really have to want it.” 

“A few weeks ago, I found myself in a Mercedes repair shop, and noticed a window motor lying on the table.  Dang if 
it didn't look exactly like the one I put in my XJ-S.  Which leads me to speculate: How many other cars use the same 
motor?  Audi?  BMW?  Volvo?  Saab?  Opel?  A wrecking yard Bosch motor in conjunction with a new Jaguar 
window regulator may be just the ticket for replacing those crappy Delco motors without bleeding from the ears at 
Jaguar's price.” 

“The Bosch motor's drive gear has a different number of teeth, so the regulator gear of the Delco won't mate with it, 
thus the need to replace the regulator.” 

 

BOSCH ELECTRIC WINDOW GEAR FAILURES:  On the 1990-on Bosch units, the gears strip.  Matthias Fouquet-
Lapar says, “I almost fell flat on my face when the workshop told me that the window motor for a ’91 XJ-S was more 
than $800!  They found a way to adapt the older motor type.  They told me that there is some nylon drive gear which 
easily breaks and there is no good fix available, so they retrofitted the older type motor.  It seems to require some major 
rework to the window mechanism though.”  Considering all the trouble Peter Cohen went to in upgrading his Delco 
motors to the later Bosch (see above), he probably doesn’t want to hear that shops are doing the reverse. 

 
 

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Hugo Guerra reports that the window motors from a ’76 fit just fine in his ’90. 

 

ELECTRIC REAR WINDOWS -- CONVERTIBLE:  Trish Duffy says, “On the convertible, the two back windows 
automatically retract when the hood/top is lowered, and close when the hood/top is raised.  These back window motors 
can burn out if the top raise/lower switch is held "on" for too long.” 

Larry Barnes says, “My 1992 convertible has a "Delco of England" window motor for the Rear\Side windows.  I tried 
to order just the motor, but Jaguar wanted to sell me the whole shooting match (with regulator) for $360.  I found a 
local motor shop the would rebuild the motor.” 

There apparently are other problems with these windows, though.  Andrew Corkan says, “I have a ’91 XJ-S convertible 
and the rear window, lowered automatically when the hood (convertible top) is lowered, stopped working.  The 
window remained up, but otherwise the operation of the hood was not affected.  I tested the usual, relay and fuse, etc... 

“Following the Jaguar service manual, 1974-88, vol 4 page 76-11, I removed the rear quarter trim panel.  I then 
removed the plastic motor cover.  It is held in place by both adhesive and three plastic button fasteners.  I missed one 
fastener and broke the thin plastic cover.  I also unplugged the two motor wires. 

“The failure was in the gearbox on the motor.  The gearbox has a thin metal plate that covers a worm gear on the motor 
coupled to a plastic gear that couples to the window movement linkage.  I removed the four bolts that hold the window 
linkage to the body.  I lowered the window half way by hand and rotated the linkage to remove it from the recess in the 
body. ( I did not remove the rear storage compartment or the hood lift linkage as stated in the service manual. ) 

“I don’t know why the gearbox failed.  The gear box contains a rubber coupling consisting of 6 pie-wedge shaped 
sections that couple a three-pronged part on the plastic gear with a three pronged part on the metal shaft that runs out 
the back of the gear box.  These wedges had popped out and knocked off the gearbox cover.  It appears that the window 
motor is just run for a fixed amount of time and there is no switch to stop it, so maybe the rubber parts were just 
squeezed out when the motor stalled at the end of the travel.  I saw no limit switches. 

“I jammed the rubber back in place and replaced the metal cover and peened that back into place.  When reinstalling the 
motor it is important to run the hood up or down so that the other window is in the halfway position (as per the service 
manual).  This puts the window linkage in a position that allows access to all three mounting bolts for the gearbox.  I 
repacked the gear box with general purpose grease, and added lithium grease to the linkages. 

“It worked fine 6 times (up or down) last weekend.  So far so good. 

“The critical and possibly breakable part appears to be the plastic gear in the gearbox.  All other parts are robust metal 
or easily cut rubber.  If you find these gear boxes, keep the parts. 

“The motor looked generic.  If it fails it should not be too tough to find a substitute, just be sure you save the worm gear 
that is on the shaft. 

“My time was 3.5 hours, mostly trying to figure out which screws to remove and how to remove the linkage.  Next time 
it will take about 1 hour.” 

Larry Barnes says, “I just got to repair the left rear window motor on "her" '92 Convertible.  I also had this same 
problem with the right rear window motor.  Dare I say it, "a design flaw"???  No, couldn’t be... 

 “Seems in the gear box (the flat lid pops off for easy access) there is a ring gear and a worm gear and a output linkage 
linked to the ring gear with a 1/4" flat/round rubber pad/shock absorber.  Well, there are three little "ears" on the rubber 
shock absorber that will break off and, get caught in, and jam up the works (always with the window in the down 
position when you are 40 miles from home and it's pouring down rain).  They seem to have no other practical  use! 

“The fix is:  Remove the FOD, spin around 3 times anti-clock wise, and reassemble.  Everything works great again...” 

 

ELECTRIC REAR WINDOWS (CONVERTIBLE) -- ACCESS:  Julian Mullaney says, “I was buggering about with 
my XJS Convertible rear windows which wouldn't work properly (just like everyone else's) and noticed that the panel 

 
 

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that covers the motors is held in by several screws, one of which is behind the window glass.  If the window ever gets 
stuck in the up position, or any position except all the way down, this screw would be utterly inaccessible, i.e. behind 
the glass.  This means that the interior leather panel could not be removed and the motors could not be accessed at all.  
One would be truly screwed if this were to happen.  I think I will leave these screws out next time.  There are enough 
other screws holding the panel in place.” 

Andrew Corkan responds, “It happened to me.  I went to my basement and found a philips screwdriver tip, the kind you 
buy in packs of 6 for driving drywall screws with your electric drill.  I then went to my local Service Star store and 
bought a strip of steel, 1/2 inch wide and 1/8 inch thick.  I cut the philips part off the driver and drilled a hole in the strip 
of metal and brazed in the stub of the philips screwdriver into the hole.  This gave me a right angle screwdriver, with a 
bend able handle, that was flat enough to get into the space.  I could rotate the screw 90 degrees at a time and it took 15 
minutes to get it out!  If you do this be sure to file all the sharp edges off the metal; I then wrapped the metal in plastic 
tape to prevent damage to the leather.  Before I replaced the screw I cut it off so it will only take two rotations to get out 
of the hole.  Now that I think about it, maybe I will replace it with a hex head screw, easier to turn.” 

 

 

Electric Mirrors

 

 

ELECTRIC MIRROR DISASSEMBLY:  Sorry to say, the electric mirrors were never intended to come apart.  Here’s 
how they went together:  The plastic rim was put into place, then the motor assembly was put in over it, and then three 
screws were put in through holes in the mirror platform to hold all that to the housing.  Lastly, the glass itself was 
mounted on the platform with foam tape -- completely covering the access holes to the three screws.  Your chances of 
getting the glass to peel off of the plastic platform without breaking it are slim.  Of course, if the entire reason you’re 
reading this paragraph is because your glass is broken and you wanna know how to replace it, that’s the trick -- just 
bust the glass into lots of little pieces until you can poke holes in the foam tape to get to the mounting screws. 

If you don’t wanna break the glass, you have a bit of a task ahead.  Fortunately, you can easily see just how difficult it 
is before you even start.  Run the electric mirror to the full up position, and pry it upwards a little more with a 
screwdriver and look under it.  You will see two Phillips head screws.  These two are not that difficult to get to.  Run 
the mirror to full down and look between the top and the edge of the housing, and you should see the third Phillips 
screw dead center.  This one’s a real pain, since it’s farther away from the edge than the lower two.  Trust me, getting 
these three screws out and back in is the only difficulty with removing the motor assembly; if you can figure out how to 
do that, the rest is cake.  The mounting lugs on the motor assembly are open slots, so removing the two bottom screws 
and just loosening the upper one may work. 

As long as you have the thing out, a couple of suggestions:  First, the plastic rim may have flashing tabs around the 
edge of the inner rectangular opening, notably at the 3 o’clock and 9 o’clock positions.  These tabs may interfere with 
operation of the mirror, and should be cut off.  In fact, it isn’t a bad idea to use a sharp blade to cut about 1/8” off the 
right side of this opening, enlarging the entire rectangle. 

Second, the motor assembly mounts with three lugs, but there is a fourth unused lug that gets in the way during 
assembly.  You may want to just cut this fourth lug off to ease reassembly.  It does nothing for operation, though, so 
you also might just leave it alone. 

Third, the bottom center portion of the plastic rim distorts, so the screws tend to pinch the mounting slots right on the 
edge rather than getting a secure grip.  My solution for this was to attach a 1½” length of popsicle stick to the bottom 
center of the housing with a piece of aluminum tape.  This holds the plastic rim up into the proper position while the 
bottom two screws are tightened. 

Note that the motor assembly itself is also permanently assembled, by melting tabs.  You’ll have to grind them off to 
get it open, and then contrive some other method to hold it shut again. 

The motor assemblies for the left and right sides are exactly the same, not mirror images or anything.