Jaguar XJ-S. Service manual - part 57

 
 

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Alex Dorne fit an electric fan from a Saab 900 Turbo and says it “replaced, and even looked better, than the original 
when in place.  The diameter was perfect, giving about 1/4 of an inch air around the propeller.  And after removing a 
metal protective ring around the prop I could use what was left of the mount and bolt the fan to the shroud using the 
upper rh and lower holes.  I also think this fan flows more than the original since it’s designed to cool a Turbo engine 
all by itself.” 

“The Turbo fan motor is flatter than on the non-Turbo because the lack of space between the radiator and the engine... 
the flatter design leaves even more space between the fan and the engine in the Jag than the original fan did.” 

The author used a fan from a Mercedes sedan of some sort.  This was a “puller” style fan, but in the Mercedes it had 
been installed in a “pusher” location, in front of the radiator.  It was the only fan cooling the Mercedes; small but 
extremely powerful, far more powerful than the OEM Jaguar fan.  It was also very ruggedly constructed.  It did require 
some bracket fabrication to hold it in place. 

Duncan Smith says, “UK list subscribers may be interested to know that the fan from an MGB will fit with only a 
couple of minor mods (the shaft needs shortening and a hole drilling through it).  The substitute fan was £40. 

“One (big?) drawback is that the rear of the motor housing is open, unlike that on the Jag motor (not that its being 
sealed protected mine from corroding and finally seizing!).  My mechanic sealed it up with tape which he swore would 
be good for the life of the car (maybe he's dropping a hint ;-).  I am not entirely convinced, but given the price of the Jag 
part and the age of my car I am not too bothered...” 

John Goodman reports that the XJR-S has a different 11” fan than the basic XJ-S:  “Seven blades high CFM part no. 
EBC 4553.  No part no. listed for the fan shroud so would imagine it could be retrofitted.”  You can draw your own 
conclusions about why Jaguar would go to the effort of providing a different fan. 

 

ELECTRIC RADIATOR FAN SWITCH:  There are apparently at least three different switches that have been used in 
the XJ-S.  Up through VIN 101854 (mid-’79), switch EAC1322 pressed into a rubber grommet in the water pump inlet. 
 I think this type of switch is called an “otter switch”.  From VIN 101855 to VIN 151087, switch EAC2510 threaded 
into roughly the same location on the pump inlet, so clearly the pump inlet was changed to provide a threaded hole.  
After VIN 151087, switch DBC2145 was used.  It is unknown what the difference between the last two switches is, 
since they both fit into a threaded hole; perhaps they turn the fan on at different temperatures.  Peter Cohen says, “The 
thermal fan switch from my ’89 XJ-S says 85º C.  It also says 909-6 and EAC2510.” 

The difference between EAC2510 and DBC2145 might also be in the connector styles.  Cohen reports:  “Beck-Arnley 
lists the same part number for the 85-91 XJ-S V12 as for the 88-90 XJ40.  This part is actually an XJ40 part.  It has two 
wires that are potted into the switch itself, leading to a cylindrical plastic connector (2 inches long by 1 inch diameter). 
This part can be used in the XJ-S V12 by cutting off the connector, and attaching blade connectors to the switch wiring. 
 This part may also be correct for the 92-96 4.0L XJS 6 cyl. 

“The Jaguar dealer quoted $122.50 for the XJ-S switch.  The Beck-Arnley part is just under $30.  Here are the catalog 
listings for some other sources for XJ40 fan switches that should be in the same price range: 

Beck-Arnley 
XJ40 and 85-91 V12 

201-1151 

 

Four Seasons (Division of Standard Motor Parts) 
XJ40 36538 
 

NAPA 
88-90 XJ40 

FS-222 

Note that the original switch has connectors right on it -- which is a real pain to get the spade connectors on and off of.  
Since this XJ40 switch has wires that you put spade connectors on the end of, it should be easier to connect the harness 
to. 

 
 

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Would the XJ40 switch replace both the DBC2145 and the EAC2510?  Unknown.  However, Cohen claims the elbow 
itself, EAC3195, apparently didn’t change, so it should thread in. 

If you have an early car, do you really want to put in a new otter switch?  Well, if it were my car, I wouldn’t.  Instead, 
I’d consider buying a new pump inlet EAC3195 (or threading the hole in the original inlet where the rubber grommet 
went) and fitting the later switch.  Failing that, it may be possible to wrap a piece of bailing wire around the inlet elbow 
to securely hold the otter switch in place, but make sure that the bailing wire doesn’t short out the connectors on the 
switch. 

 

ELECTRIC RADIATOR FAN RELAY:  As mentioned on page 561, the electric radiator fan relay is an SPDT relay 
(red to indicate it’s different), meaning it has a central fifth terminal labelled 87a - a NC contact.  In this particular 
application the 87 contact is 12V power and the 87a contact is connected directly to ground.  As a result, if a relay with 
two 87 terminals or one 87 and one 87b terminal is plugged in, a direct short will result and fuse #1 in the headlamp 
fusebox will blow immediately. 

The NC contact shorts the fan motor to ground when not operating.  It’s not known why Jaguar did this.  If a 4-terminal 
relay that has no center spade terminal is installed, the system seems to work fine; the fan operates normally when on, 
and the fact that the fan is not grounded when off doesn’t seem to make any noticeable difference.  However, it seems 
unlikely that Jaguar would have gone to the effort of supplying the grounding circuit without a good reason.  

 

ELECTRIC FAN DIODE PACK:  The blue item mounted on the top left side of the engine compartment just rearward 
of the diagonal strut looks like a relay, and has the same spade terminal layout as a relay, but it’s not a relay at all; it’s 
the diode pack for the electric fan.  The terminals are numbered simply 1, 2, 3, 4, and 5.  You can easily pry the box 
open with a small screwdriver and inspect the layout inside. 

Diodes merely allow current in one direction only.  When testing this pack, you should be able to get current to flow 
from terminal 3 to terminal 1 but not the other way around.  You should also be able to get current to flow from 
terminal 5 to terminal 4 and from terminal 2 to terminal 4, but not the other way on either.  This description uses the 
accepted definition of current as flowing “from” a + terminal to a - terminal.  Note that some meters may not incite a 
diode to flow in either direction when set to a standard ohmmeter setting; if the meter does not have a setting for testing 
diodes, it might be better to use a battery and a light bulb to test. 

In case you haven’t developed a healthy disrespect for Lucas engineering yet, here’s another example of their 
handiwork: the wires that connect to terminals 1 and 3 are both GN, but they are different and you’d better not mix 
them up!  Likewise, the wires that connect to terminals 2 and 4 are both LG, but don’t mix those up either! 

If you’ve already disconnected them and gotten confused: on the author’s ’83, the GN wire that connects to terminal 1 
is actually two wires attached to the same spade connector, while the GN that connects to terminal 3 is a single wire.  
Likewise, the LG wire that connects to terminal 2 is actually a pair of wires, while the LG that connects to terminal 4 is 
a single wire.  Here’s hoping other cars are the same! 

I will describe more elaborate tests, in case the above proves inadequate.  If you apply 12V to a GN wire and the 
electric radiator fan starts running, that wire connects to terminal 1.  If the clutch on the A/C compressor engages, it 
connects to terminal 3.  If the engine is cold and you turn the ignition on and read 12V at a LG wire, it connects to 
terminal 2; if not, either a fuse is blown or it connects to terminal 4. 

Just when you thought you had these things figured out, Jaguar goes and does something totally unexplainable.  Michel 
Carpentier reports on the diode pack in his Daimler Double Six:  “The blue box is clearly the same as described in your 
book: one diode with anode in 3 and cathode in 1; two diodes with anodes in 2 and 5, common cathode in 4.  But it 
provides the logic for the headlamp wash/wipe system.  2 is connected to a blue/red wire (high beam), 5 to a blue/white 
wire (low beam), 4 goes to terminal 85 of the wash/wipe relay via a blue/red wire.  1 has a green/blue wire going to one 
of the washer pump terminals.  3 has two green wires, live when ignition is on.  Terminal 86 of the headlamp 
wash/wipe relay is connected to the other terminal of the washer pump (common to windshield and headlights) and to 
the windshield washer switch.  When you push the windshield washer switch, terminal 86 of the headlamp wash/wipe 

 
 

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relay is grounded and the pump operates via diode 1/3.  If the headlights are off you get normal windshield washer 
operation.  If they are on (either low beam or high beam) 4 is live so the relay is energized: the headlamp wiper motors 
kick in and valves open, squirting fluid on the outer headlights.  Much ado for a perfectly useless gadget! 

“Back to the cooling fan.  Against the radiator is a small harness which comprises the following: A green/brown wire 
running from a connector on the RHS of the radiator (said connector linked to A/C compressor clutch) to terminal 86 of 
the red fan relay.  Somewhere in between, this wire is cut and a small PCB (about 30x8mm) holding a diode soldered 
in, with the cathode towards the relay.  Terminal 86 of the red fan relay is also connected to the thermostatic switch by a 
green/white wire.  A black wire connects terminals 85 and 87A to ground.  A brown/green wire comes from the main 
harness on the LHS (live at all times) and goes to terminal 87.  Another small PCB (exactly 32x10mm) is also buried 
inside the harness. It holds two diodes with a common cathode connected to the thermostatic switch by a green/orange 
wire.  One anode has a red wire going to terminal 30/51 and thence to the fan motor.  The other anode is connected to 
the main harness by a green wire (live when ignition is on).  This harness is held together by the usual weaving: 
outwardly there is no way you can tell that it is so electronically sophisticated as to contain 3 diodes!” 

Craig Sawyers says, “Curiously, it seems that some detail went into the choice of diodes in the fan control and 
headlamp wiper circuits (the blue box with four terminals).  The diodes are all soft recovery devices, which are 
specifically designed to eliminate fast voltage spikes when they switch off (caused by junction capacitance in the diode 
itself).  I took the lid off just out of curiosity some time ago, and they are all quite distinctive (BUV something or other). 
 When I looked them up they are quite specifically soft recovery diodes each with different ratings, designed to reduce 
the transient interference when they switch off.  I was quite surprised at the obvious care that had been taken in the 
choice of components.” 

Peter Cohen talks about the later cars:  “The facelift model cars have a different setup to the 1991 and earlier cars.  The 
later cars have a completely different diode pack.  It will be in approximately the same location.  Most relays are 
manufactured by Hella or Bosch.  If you see a component made by someone other than Hella or Bosch in that general 
vicinity, it is worth a look.  It will have one BG and two LG wires.” 

 

LATE MODEL ELECTRIC FAN OPERATION:  Bruce Segal reports:  “I believe Jaguar changed the design in 89 so 
that the fans no longer come on with the A/C compressor.”  Wise?  Many owners don’t think so, and rewire the fan the 
way the earlier cars were wired so the small electric fan comes on with the compressor.  You can read all about the 
benefits of optimum airflow through the A/C condenser on page 514. 

 

FAN SHROUDS:  The fan shrouds ensure that air drawn by the fans comes through the radiator rather than other 
places.  If the fan shroud is not installed properly and held securely against the back of the radiator, then air from the 
engine compartment can be drawn in by the fans.  This short-circuits the airflow and reduces the amount of air coming 
through the radiator. 

Anytime there are two fans and one may be on while the other is off, it is also important that the fan shrouds provide a 
separation between the two so that air draw by the running one doesn’t simply come backwards through the non-
running one. 

 

FAN SHROUD FLAPS:  At the lower left corner of the XJ-S fan shroud are a couple of rubber flaps.  These are 
designed to allow air to flow rearward through the openings in the shroud but not forward.  At speed, the air coming in 
the front of the car and through the radiator merely blows these flaps open.  At a standstill, when the fans are trying to 
draw air through the radiator, these flaps shut to prevent the fans from drawing air from the engine compartment 
instead. 

They’re as simple as they look.  If they are damaged or missing, it is easy enough to make replacement flaps from an 
old inner tube, or even old shoe leather. 

 

 
 

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FOAM IN AIR PATHS:  In order to ensure that air coming in the front of the car goes through the radiator, any 
passages around the radiator must be plugged; air would much rather take an easy route, so even a small gap will allow 
a large portion of the airflow to bypass the actual heat transfer area.  Also note that the space between the radiator and 
the A/C condenser/oil cooler must be sealed all around, so that the fans draw air through the A/C coil and oil cooler 
rather than in through a leak path.  And, of course, air coming in the front of the car should be compelled to go through 
the A/C condenser/oil cooler rather than sneaking past it as well. 

There is a second reason to apply the foam in the nooks and crannies around the A/C condenser and oil cooler.  As 
mentioned on page 202, the space in between the condenser/oil cooler and the radiator itself is often found to be 
plugged up with debris.  While the difference in coarseness between the condenser/oil cooler and the radiator may 
permit a particular range of grit sizes to get in there, the fact is that this space is usually found to be full of leaves -- far 
too large to have passed through the condenser coils.  They can only be getting in there by sneaking through openings 
that should have been plugged with foam. 

Jaguar used foam to plug some of these openings -- a British nonmetallic material.  If your radiator seems to have no 
such foam anymore, Thomas Alberts says, “Most of the mail order places do not carry these "gaskets" (as they are 
called in the parts book), however they can be purchased from Jaguar dealers for a few bucks.  The part numbers (for 
my 1987 XJ-S) were CAC2321 for the side and CAC3821 top & bottom.” 

Alternatively, go to the building supply store and purchase one package of 2-1/4” x 2-1/4” x 42” foam intended for 
sealing window air conditioners and at least one package (maybe two) of 1/2” thick 3/4” wide weatherstripping foam 
tape.  For the tape, you may have a choice between “open-cell poly” and “closed-cell vinyl”; either will probably work 
fine.  You may also buy a couple other thicknesses of foam weatherstripping while you’re there, just in case. 

Doing a proper sealing job is easier if you have a lot of stuff apart in this area.  For example, having the fan shrouds 
removed helps, and having the radiator upper support rail off is also a big help.  Ideally, do this job while you have the 
radiator itself out.  But if you’re not doing that kind of work today, don’t postpone sealing the openings until you do; do 
your best with what you can, and if necessary buy some more foam later when you have things apart. 

If you have the radiator out, start by applying the foam tape to seal the bottom of the radiator between the rubber 
support grommets and outboard of the grommets to prevent air from sneaking by under the radiator. 

Cutting the 2-1/4” foam with a razor knife, install a piece on either side of the radiator to fill the huge gaps there.  Install 
the foam in front of the radiator itself, beside the A/C condenser/oil cooler.  If positioned properly, it will seal against 
both by fitting snugly against the ends of the A/C condenser and against the front of the header on each end of the 
radiator.  Make sure the pieces stand high enough that the upper radiator support rail sits down on them when installed. 
 The foam can be fit behind the supports for the front bumper crash absorbers all right, but you’ll have to end it where 
the pipes connect to the oil cooler.  Then cut a couple more chunks from the remainder of the 2-1/4” foam to fill in the 
openings under the pipes to the oil cooler. 

From the remainder of the 2-1/4” foam, cut a piece about 6” long and then cut it lengthwise at a slight angle to create 
two wedge-shaped pieces of foam.  Use these to fill in the space on each side near the top where the 2-1/4” foam wasn’t 
fat enough to completely fill in the space.  If you have wiring or hoses passing through here, you can arrange them to 
go between the pieces of foam so they are nicely supported.  You can cut suitable recesses in the pieces of foam to 
make way for the freon line coming around the top right end of the radiator. 

Looking through the lower grille in front of the car, you will notice that there are two more gaps created by the fact that 
the oil cooler is not as long as the A/C condenser.  Cut two blocks of foam and insert them by reaching right through 
the grille. 

There is also a gap between the bottom of the A/C condenser and the top of the oil cooler.  This gap should be plugged, 
even though it never was originally.  This seems counterintuitive, since it’s directly in front of the radiator and it would 
seem that plugging this gap would reduce airflow through the radiator.  That’s not the problem, though; the problem, 
besides allowing air to bypass the A/C condenser and the oil cooler, is that this gap allows leaves and other debris to 
pass through and get lodged in the space between the radiator and the oil cooler.  This has proven to be a far more 
serious concern for XJ-S owners than any reduction in airflow that might result from sealing this gap.  Fortunately, 
sealing the gap is really easy; just cut a piece of weatherstripping to a suitable length and cram it in there.  If you use