Jaguar XJ-S. Manual - part 156

 
 

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You can accomplish very close to the same effect by merely installing a shorter blade on that arm.  A blade one inch 
shorter will pull the tip away from the A pillar the same amount as shortening the arm by 1/2”.  Unfortunately, it also 
reduces the area of the windshield that gets wiped.  This may or may not be a problem for you. 

Another improvement can be made by bending the arm slightly.  The arm that parks over the other is cranked a little bit, 
but the one that parks pointing toward the A pillar is straight.  Take that straight one, mount it in a vice, and crank it 
kinda like the other one.  It’s as difficult to bend as it looks; you’re bending a flat bar the hard way, but the metal is soft 
and bends easily.  This bend allows you to set this arm to park lower without the bottom end hitting the trim at the 
bottom edge of the windshield -- but it does nothing for the contact with the A pillar.  So, it’s a good plan to make both 
changes -- shorten the arm a bit and crank it a bit. 

Another possible solution is to alter the wipers so they park on the passenger’s side.  In the case of the later Electrolux 
motor Stefan Schulz says this can be done by merely opening the motor gearbox and moving the park cam 180 degrees, 
but it doesn’t look that easy on the Lucas motors.  You will need to purchase Jaguar wiper arms that have the bend the 
opposite direction.  Of course, after all this the wipers will still be just as obtrusive, but they will be aggravating the 
passenger instead of the driver. 

 

Windshield Wipers -- Lucas Solenoid-Park 

 

SOLENOID-PARK OPERATION:  Mike Morrin reports on the early XJ-S wipers:  “The wiper in question has a 
highly (over) engineered parking facility where on the parking stroke, the blades go an extra 5 degrees or so, which 
pushes them off the screen onto the chrome strip.  In the parked position, the blades are on the glass for about half their 
length, and on the chrome strip for the other half.  Definitely further out of the driver’s field of view than where you 
would put them on a normal wiping stroke.  The early cars had this feature; the pictures in the pre-HE parts book and 
the service manual both show the solenoid (although it is not labelled in the parts book and the service manual calls it a 
switch).” 

The “Extract 3” wiring diagram in the back of Section 86 in the ROM and Fig. 10.128 and 13.96 in the Haynes manual 
include schematics for this system.  The solenoid is not labelled, but it’s the coil-lookin’ thing alongside the motor. 

Richard Dowling describes how it works:  “In “OFF” position (park position) no power is applied to the motor or 
solenoid.  In “LOW” or “HIGH” speed position +12V is applied to the motor windings through yellow (high speed) or 
red (low speed) wires.”  Note: the low speed wire from the stalk switch to the bulkhead connector is ULG and from the 
bulkhead connector to the microswitch it’s blue.  Inside the microswitch it does nothing but come out another terminal, 
and from there the low speed wire to the motor itself is red on Dowling’s car, but in Fig. 13.96 of the Haynes it’s BLG. 
 Doncha just love Lucas wiring? 

“As soon as the motor moves away from the park position the microswitch is closed and this maintains +12V on the 
“2” contact of the stalk switch.”  Note that Fig. 13.96 in the Haynes numbers the terminals on the stalk switch 
differently for some reason, with the terminal that gets 12V from the microswitch being number 1 instead of number 2. 

“The motor shaft has a small worm which drives a large gearwheel.  On the gearwheel a cam is mounted, and this cam 
has a pin which connects to a crank arm.  The cam is concentric with the gearwheel in normal wiper arm motion.  As 
the cam and gearwheel rotate the crank arm moves the wiper arms in an arc over the windscreen. 

“When the stalk switch is returned to “OFF” position, +12V from “2” contact will both maintain the low speed motor 
winding energised and also energise the solenoid.  The solenoid operation activates a catch to engage a spring loaded 
lever on the cam.  This in turn forces the cam into eccentric operation on the gearwheel, which moves the crank arm 
over a longer stroke and thus activates the microswitch to open the “ON” contact and hence remove power from “2” 
contact on the stalk switch.  The motor winding and solenoid are then de-energised and the wiper arms are in the park 
position. 

“As soon as the motor starts up again the eccentric cam rotates to its normal concentric position on the gearwheel. 

 
 

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“The microswitch position is adjustable in a slot with a small screw to determine where it stops the crank arm.  Opening 
the “ON” contact stops the motor which stops the crank arm. 

“The microswitch body has 8 “faston” terminals, but only 2 terminals are effective.  Those 2 are the common pole 
of the switch and the “on” contact.  The other terminals are only for interconnecting wires.” 

Morrin:  “It is nearly a good design, suffering only from the poor thermal design of the solenoid, and perhaps the 
parking switch should have been operated by a cam on the driven gear rather than by a switch on the sliding link 
thingy.” 

Note: the cars with the solenoid-park wiper motors did not have an intermittent mode.  This may help explain the 
changeover to the reverse-park motor used later, since the solenoid-park scheme would probably not work well being 
parked every ten seconds or so. 

 

WON’T PARK:  Dowling:  “Ever since I bought this car there have been times when the wipers would stop dead on 
the windscreen when switched off instead of parking.  I know it is a problem with the switch fitted to the wiper 
gearbox.  The switch is supposed to keep power on the motor until it reaches the park position.”  Unfortunately, since 
Jaguar took to replacing these wipers in entirety with the later reverse-park wipers; buying a new microswitch is likely 
to get more and more difficult as time passes. 

“The overall wiper motor/gearbox is a fairly solid design and mine looks almost brand new after a clean up, oil and 
grease.  Even the quirky solenoid that pulls in a ramp, that pushes up a latch, that forces the drive wheel into an 
eccentric orbit that then parks the wiper arms usually works.  Strange but true - at least on my car. 

“However, the switch gadget, which is a homegrown Lucas thing, is a pathetic cheap addition to what is a fairly good 
and expensive piece of machinery.  I have pulled out the wiper assembly at least half a dozen times over the years to see 
if I could do anything to make it work reliably.  It is not so easy to fit a microswitch in place of the Lucas POS, since 
you need a bracket to mount it and there is really no easy place to fit a bracket on the body of the wiper gearbox. 

“I lopped off the top of the Lucas switch and exposed the little plunger in there which is operated by the cam on the 
slider in the gearbox.  Luckily this leaves a hole in the Lucas item where you can put a miniature style microswitch.  
These are smaller than the regular size used on the throttle kickdown but not too hard to get hold of at US$3 a time.  I 
made a simple bracket from aluminium angle and glued it to the Lucas POS. 

“Drilled a couple of holes and mounted the microswitch.  The microswitch has a short lever with roller and is pushed 
up by the plunger.  Reasonably easy in the end.” 

 

AVOIDING THE WON’T PARK PROBLEM:  Regardless of whether you’re trying to preserve the original Lucas 
switch inside the solenoid-park motor or you’ve already replaced it with a generic microswitch as described above, 
you’ll see the value of reducing the stress on the contacts inside to help that switch last as long as possible.  Its job is to 
break contact to not one but two inductive loads: the solenoid and the motor.  As discussed beginning on page 557, 
inductive loads tend to cause charring on contacts when disconnected -- but it’s really easy to prevent this by adding a 
diode.  You should add a diode here.  Now. 

When looking at the wiper motor assembly, there are two wires that go from the microswitch to the solenoid: one blue 
and one brown.  This is a convenient place to add the diode: between the blue and brown wires, with the point or stripe 
on the diode towards the brown wire. 

This isn’t the only place it could go.  It could also go inside the car in the wiring to the stalk switch.  It needs to be 
wired in between the RLG wire and ground, with the point or stripe towards the RLG wire. 

Remember that even though you might be installing this diode in the wires to the solenoid, it’s not just spikes from the 
solenoid it’ll be absorbing; it’ll also be absorbing spikes from the motor, which is connected in parallel to the solenoid 
when the microswitch turns them both off.  So, you need to make sure this diode is big enough to handle that job.  As 
described in the section on installing such diodes, none of them ever need to be very big, but don’t put a really tiny one 
here. 

 
 

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Note:  The relay installation described below will also help the microswitch last longer -- but it’s no substitute for 
installing this diode.  The diode is probably more important to this switch’s life.  Of course, doing both would be a good 
plan. 

 

WON’T STOP -- CAUSE #1:  Dowling:  “If the microswitch is too far down its slot, or the switch contact does not 
open, the motor and solenoid stay energised and the wiper arm will not park.  In fact the wiper will operate whenever 
the ignition is on.  This is a very obvious fault and may burn out the solenoid if it is not fixed promptly.”  By promptly, 
he means within a minute or so.  As Morrin mentions below, if it won’t stop you need to move the stalk switch back to 
low speed position to avoid frying that solenoid. 

 

WON’T STOP -- CAUSE #2:  Morrin:  “Unfortunately, a little bit of dirt or grease in the wrong place is enough to stop 
the solenoid pulling in all the way, which prevents the eccentric gear mechanism from pushing the wipers off the edge 
of the screen, which means that the parking switch doesn't get activated, which means that the wipers keep going and 
going and.....  fried solenoid.”   

The parking solenoid gets fried “because it is designed to be energised only while the wipers are switched off and are 
not parked.  The designer thought that this period would be only a couple of seconds, and designed the solenoid with 
thermal capacity for about 30 seconds. 

“If you do have an early car (pre H.E.) with this facility, if the wipers ever keep running after you have turned them off, 
then put the switch back into the ON position, or the solenoid will burn out within a minute or so.  Remove the wiper 
blades if it stops raining.”  Uhhh, it might help to shut the car off to do this.  Once the wipers are in the trunk, you can 
start it back up and drive off with the wiper motor whirring merrily away.  Alternatively, you might simply opt to shut 
off the ignition when the wipers are in the right place, and then remove the correct fuse before starting it back up.  Fuse 
9 should do it. 

“If the solenoid has not melted, the parking function can probably be restored by carefully dismantling, cleaning and 
reassembling the solenoid.” 

If the solenoid has melted:  “I stripped off the old wire and built up the melted plastic core with epoxy filler, then filed 
it back to shape.  The solenoid is wound with 0.16mm (0.0063") copper transformer wire.  I didn't count the turns, but it 
does need to be neatly layer wound or you cannot fit enough turns to get the required magnetic pull.” 

 

QUICKIE FIX FOR FRIED SOLENOID:  Morrin: “I found that the parking switch is adjustable, and by trial and error 
found a position where the wipers would stop more or less at the bottom of the screen when switched off, even with the 
parking solenoid removed.  This solution was almost perfect except that with the blades fitted so that they parked at the 
bottom of the screen, they did not wipe all the way to the passenger side of the windscreen.” 

 This quickie fix might even be considered an improvement.  Per Morrin, the correctly-operating solenoid system “takes 
about half the period of a normal stroke to move the the wipers through the first 5 degrees, and you need to hold the 
switch for that period of time.” 

 

UPGRADING TO LUCAS REVERSE-PARK:  If you’re interested in upgrading an earlier car with the later wiper 
motor, Scott Horner describes “the little Lucas blue box modification - this plugs into the original wiring loom and fits 
into any tight spot under the dashboard.  This was offered by Jaguar to make the windshield wipers park on pre-H.E. 
cars, when used in conjunction with an H.E. wiper motor.” 

 

RELAYS:  The pre-90’s XJ-S is notorious for powering high-current loads such as electric windows and windshield 
wipers through tiny contacts and long, skinny wires.  The result is a 14V load that is trying to operate on 8V or some 
such, the rest of the voltage being lost in the controls and circuitry.  If your wipers are dragging, the solution is to 

 
 

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provide a relay scheme to provide solid power directly from the main power bus and use the original control wiring 
only to control the relays. 

Dowling suggests there may be another good reason to install relays: to help the stalk switch last longer.  It’ll also help 
the microswitch in the motor last longer.  If either of those switches ever gives out on you, you’re gonna wish you had 
ponied up the ten bucks for relays when you first read this. 

It’s very simple to install relays on the solenoid-park motor, only requiring two relays -- one for low speed, one for 
high.  There are three wires from the microswitch to the motor itself.  One of these is a ground wire; Dowling says that 
one is blue.  For each of the other two, pull the spade connector off the microswitch and connect it to a normally-open 
contact on a relay.  Connect the terminal on the microswitch to one coil terminal on the relay.  Connect the other coil 
terminal on the relay to ground; that third wire on the motor is a ground, so you can splice into that or piggyback onto 
the terminal it connects to.  Connect a stout 12V power lead to the other side of the normally-open contact. 

Obtain that stout 12V power from the main bus on the firewall.  You’ll need to provide a fuse within the engine 
compartment where it’s easy to get to, and then run the lead into the wiper compartment and install the relays in there 
somewhere they won’t get immersed when it rains. 

The third wire from the motor needs to be a good solid ground.  It might help a little to provide an additional 
reinforcement ground right there in the wiper compartment.  Simply tie in another wire and screw the other end down 
to the body somewhere. 

If you’d rather work behind the dash, these relays can just as well be installed in the wiring from the stalk switch.  
Merely cut the ULG and YLG wires and splice in the relays, using the lead from the stalk switch to power the relay coil 
and the contact in the relay to send solid 12V power on to the wiper motor.  You can get the stout 12V power from the 
main terminal post on the firewall near the climate control system. 

 

Windshield Wipers -- Lucas Reverse-Park 

 

SCHEMATICS:  The reverse-park wiper system is shown schematically on page 86-15 of the ©1982 Supplement to 
the ROM.  Apparently the only place it’s shown correctly in the Haynes is in Fig. 13.91 -- which is a wiring diagram 
for the saloon.  Whatever, you can simply refer to Figure 35 below and ignore the relay additions to see how the car 
was originally wired. 

 

WINDSHIELD WIPER CONNECTOR AND HARNESS:  Once you have the grille out, you will find that the wiper 
motor plugs into a socket on a panel inside the grille compartment.  Jaguar uses a really nice 8-conductor plug to 
connect five wires.  You might find it helpful to know which wire on the schematics connects to which conductor on 
that plug.  Figure 34 is an illustration of the connector on the panel in the author’s ‘83, viewed as though you were 
standing on the engine looking at it.  The circles represent brass posts. 

 

Figure 34 - Windshield Wiper Connector