[xj-s] Electric Fan Not Working - HELP!

XJ-S
1

On the way to work today (in our 98+ temps) I noticed my temp
gauge slowly creeping up. It never got to the actual red zone or
the light ocme on, but I knew something was likely amiss.

When I got to the office I noticed that when I shut the engine off
the cooling fan did not continue to run for a few minutes, like it
normally does, so that is apparently the problem. I have never had
problems with it before.

I will be checking the fuse for the aux. fan later today when the
engine has cooled a bit, but assuming it is not blown, where should
I look next? I’m thinking there is a thermostatic relay somewhere
that hooks into the water jacket (or possibly to a temp sensor).
Where is it at and how can I test it without my multimeter here?

I don’t think it 's a good idea to be driving around in these
temps (esp.) w/o the aux. fan working.

Thanks!–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
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2

In reply to a message from AttyDallas sent Wed 24 Aug 2011:

Hi Paul. The thermal switch is on the left top side of the
radiator. Check the fuse and the relay first. The fuse and relay
are on the engine bay left hand side

I originally had my OEM fan wired to come on from a toggle switch I
ran into the cabin so that A/C would improve by it running all the
time. Shortly after that, the fan gave up on me.

Currently, I am running two spal pusher fans in front of the
condenser using the OEM wiring (just spliced in a couple of
connectors and upgraded the fuse to 30amp) I have a 9 inch high
powered in the area where the OEM was situated and a pancake 10
inch on the other side.–
95 AJ16 4liter 6cylinder, Houston TX
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3

In reply to a message from Mark Janzic sent Wed 24 Aug 2011:

Thanks, Mark. Which of the relays on the bank is it?

I really hate how Jaguar decided to leave the relay I.D. out of
the User Guide for the XJS (they have always included it in the
XJ40 and X-300 manuals). Also, the relays do not have marked
covers on them indicating which component they are for, apparently,
unlike the saloons. &:-/–
The original message included these comments:

Hi Paul. The thermal switch is on the left top side of the
radiator. Check the fuse and the relay first. The fuse and relay

–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
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4

In reply to a message from AttyDallas sent Wed 24 Aug 2011:

Paul here is the electrical guide for our cars:

http://www.captainjaguarscathouse.com/Electrical_Reference.htm--
95 AJ16 4liter 6cylinder, Houston TX
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5

In reply to a message from AttyDallas sent Wed 24 Aug 2011:

Should be the first relay from the front of the car.

Fuse should be the 4rth ,a blue 15 amp–
95 AJ16 4liter 6cylinder, Houston TX
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6

In reply to a message from Mark Janzic sent Wed 24 Aug 2011:

Thanks.

I just got the bad news from ML that if I have to replace the
thermostatic switch it’s almost $500! (10x the price of the one
for the V-12s, which makes no sense to me). They also have not yet
been able to find any used ones.

Possibly I can use the one off my X-300 temporarily?–
The original message included these comments:

Should be the first relay from the front of the car.
Fuse should be the 4rth ,a blue 15 amp

–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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7

In reply to a message from AttyDallas sent Wed 24 Aug 2011:

Oh my!. Its part DAC6794 . I bought one for 50.00 bucks a couple
of years ago, just so I could cut the wiring on it to adapt to my
in cabin switch…

I would not pay 500.00 for it.–
95 AJ16 4liter 6cylinder, Houston TX
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8

In reply to a message from Mark Janzic sent Wed 24 Aug 2011:

And if you are oposed to having a toggle switch in the cabin to
control the fan at your pleasure, you can aleays wire it to come on
with compressor…Directions should be onthe archives–
95 AJ16 4liter 6cylinder, Houston TX
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9

In reply to a message from Mark Janzic sent Wed 24 Aug 2011:

Oops I guess they were getting the aux motor/fan itself mixed
up with the thermo switch @ ML. The motor w. fan is about $500,
but the switch closer to $50. Unfortunately, they don’t have
either in stock, new or used.

I checked the fuse and it is O.K. I found my multimeter (was in
my boot - phew!) and would like to test the relay with it. Any
idea how to do that? Or, could I swap the relay for one of the
other ones on that same bank, since they all go to lighting stuff
(except for the air injection pump) and see if it makes a
difference?

If the relay is O.K., how do I use the multimeter to check the
thermo switch? Should the resistance across it change as the
coolant heats up?–
The original message included these comments:

Oh my!. Its part DAC6794 . I bought one for 50.00 bucks a couple
of years ago, just so I could cut the wiring on it to adapt to my
in cabin switch…

–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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10

Hi Paul,

Everything is at the left front component panel, under the bonnet. The
fuse is fuse #4, 15A, in that fuse panel, and the fan relay is the
forwardmost relay in that panel (~ 5 relays, total).

If you want to read along on the circuit diagram, (it’s really not that
hard to follow with a little practice and someone leading you through
it) go to this site and download the Electrical Guide for your 95 4.0L
and to fig. 24, Auxiliary Cooling Fan:
http://www.captainjaguarscathouse.com/Electrical_Reference.htm

Pull the relay off its base and carefully examine the underside of the
relay, next to the pins, for pin numbers: 30, 85, 86 & 87. Now examine
the relay base, and you should find that there are Brown/Green wires
going to pin sockets 86 & 87, a Black/Green wire going to pin socket
30, and a Green/Brown wire going to pin 85. The “Brown/Green” wires
are predominantly Brown, with a Green stripe or tracer, and the
“Green/Brown” wire is predominantly Green with a Brown stripe. Make
sure you note the difference, and make sure the relay pins, as
numbered, go in the sockets with the wire colors as indicated. If NOT,
check back with me BEFORE you do any of the following tests.

Once you have become familiar with the wires attached to the relay
base, and have identified each as the colors indicated above, do the
following tests (with the relay out of the base for tests 1, 2 & 3):

(1) using your voltmeter, selecting a range greater than 12V, put the
red probe on socket 87 (Brown/Green wire) and black probe on ground.
You should get 12V+, battery power (key does not need to be on).

(2) do the same voltmeter test on socket 86, and the result should be
the same.

(3) if you have battery power in each of the tests above, apply a
jumper (just a piece of plain wire) between sockets 87 and 30; the fan
should run.

(4) replace the relay in its base; apply a ground to the Black wire in
the base, and the fan should run. If you don’t have test jumper wires
(available cheap from Harbor Freight) with alligator clips, you can
just use a piece of plain wire with one end anchored to ground (good
metal or bolt on engine).

If all those tests went as described, your fan works and your relay
works. The switch is either on or off; it does NOT change resistance
with temperature like the CTS or temp gauge sender. When it is on
(contacts closed/making contact) it completes a ground to pin 85 of the
relay (Black wire) just like you did manually in test 4. Basically, if
all 4 tests went as described, if your fan is not running, the switch
is NOT closing and providing ground to pin 85.

George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: AttyDallas attydallas3@aol.com

I checked the fuse and it is O.K. I found my multimeter (was in
my boot - phew!) and would like to test the relay with it. Any
idea how to do that?

If the relay is O.K., how do I use the multimeter to check the
thermo switch? Should the resistance across it change as the
coolant heats up?

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11

In reply to a message from George Balthrop sent Wed 24 Aug 2011:

Thanks so much, George and Mark …

I THINK I may have fixed my problem, and, if so, it was pretty
simple. I went ahead and r/red the relay with a new one that I had
originally bought for my headlights (I had goofed and ordered it
instead of the Headlight Control Module sometime back). I noticed
the contacts on the old one were pretty oxidized looking (one was
even greenish), so that may have been it. I also tinkered a little
with the fan wiring and connectors in case something was loose
along those lines, and also added about a quart of radiator
coolant, which was low.

I say I t’hink’’ I may have fixed the matter, in that ‘‘so far, so
good’’ … Only problem is that yesterday was the first day we have
had temps only in the 80s (cool front moved in late afternoon), so
the fan did not kick on and, IIRC, it doesn’t usually do so unless
the outside temps are hotter, e.g. in the 90s. I should definitely
know later today if it’s working or not, as we’re supposed to reach
106! I’ll keep Supercat close to ‘‘base’’ until I know for sure.

btw, I discovered, when checking the fam connections, that,
sadly, Supercat suffers from the usual ‘‘petrified shroud flap’’
problem of older Jags. I accidentally broke one off in the process
(the top one was already missing). I guess that may also increase
cooling a bit under there (?) I just wonder why in the world Jag
never did come up with a synthetic flexibile material that would
hold up to the temps under there without turning the flaps into
solid plastic!–
The original message included these comments:

following tests (with the relay out of the base for tests 1, 2 & 3):
(1) using your voltmeter, selecting a range greater than 12V, put the
red probe on socket 87 (Brown/Green wire) and black probe on ground.
You should get 12V+, battery power (key does not need to be on).
(2) do the same voltmeter test on socket 86, and the result should be
the same.
(3) if you have battery power in each of the tests above, apply a
jumper (just a piece of plain wire) between sockets 87 and 30; the fan
should run.
(4) replace the relay in its base; apply a ground to the Black wire in
the base, and the fan should run. If you don’t have test jumper wires

–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
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12

In reply to a message from AttyDallas sent Thu 25 Aug 2011:

Well the ‘‘100-degree day’’ test reveals the aux fan is in fact NOT
working, so I’ll have to go through the testing procedure that
George provide (thanks again for that!).

Supercat is O.K. (i.e. not in the ‘‘red’’) so long as I’m not stuck
in traffic somewhere on those days, but I don’t want to temp fate.

Going on the assumption - worst case scenario - that it is the
fan motor, I have been checking around for good used ones (nobody
apparently sells new ones). I’m not finding any, but have found
plenty of XJ40 aux. fans and a few of the Series III fans … The
XJS '92-'94 aux. fans also. They all look a lot like the '95-'96
XJS aux. fan (4-blades, etc.). I guess I won’t really need the
blades anyway, just the motor. Doees anyone know if I can use any
of these model motors for mine?–
The original message included these comments:

good’’ … Only problem is that yesterday was the first day we have
had temps only in the 80s (cool front moved in late afternoon), so
the fan did not kick on and, IIRC, it doesn’t usually do so unless
the outside temps are hotter, e.g. in the 90s. I should definitely
know later today if it’s working or not, as we’re supposed to reach
106! I’ll keep Supercat close to ‘‘base’’ until I know for sure.

–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
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13

In reply to a message from AttyDallas sent Thu 25 Aug 2011:

O.K., I couldn’t I.D. the 4 wire colors to the relay b/c they are
all wrapped tightly in electrical tape (not sure if that is OEM or
what), so I did the next best thing and tried the bent paperclip
jumper trick (thanks George, btw!), figuring there are only 6
permutations to try before I hit the one that should run the fan,
if it is in fact still working.

The very first try (jumping the wires at 12 o’clock and 6 o’clock,
facing the relay) caused the fan to come on and run fine. So, it
sounds like the problem is definitely the thermo switch (right?)

I found a place online that is sending me one for $12 + $32
priority FedEx. The listing said it was actualy for '94 4.0 and
did not show it (or anything) for '95, but it looks the same and
the Jag part #, IIRC, is the same.

I’ve looked for the switch where someone said it is, on the
driver’s side of the radiator, along the side, but don’t see it.
Can anyone pinpoint it better for me (a pic would be great)?

In the meantime, I’ll leave the paperclip in place while driving
to keep the fan running constantly. Or, could I just turn the a.c.
on low to make it run (a.c. is blowing warm of late)?

btw, w/o the aux. fan running, driving w. 98 outside temp, the
temp gauge almost goes to red, but not quite. Is that normal w/o
the aux. fan working? I remember many of our XJ40 owners reporting
that their aux fans never worked (or almost never came on except in
extreme heat) and yet their gauges read just fine as to temp. My 2
were the same way (aux. fans broke). I’m wondering if something
else is contributing to the overheating situation in Supercat, or
do they just tend to be a hotter running engine?–
&:slight_smile: Paul '95 XJS cp. 238k (black), '96 XJ6 110K (black)
Garland, Texas, United States
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14

84 xjs. I just got through replacing my water pump and radiator with a the be-cool side flow radiator. My electric fan is not coming on. This post mentions there should be a thermal switch on the radiator to control that. My old radiator did not have one. The left top of the radiator just had a brass plug in it. There are two wires plugged onto the water pump housing one of which goes into the same wire bundle as the fan wire. So I was thinking that was what was controlling the fan but I don’t know. I also repaired my A/C which had a frozen compressor. I picked up one from a donor car for $20 and I evacuated and charged the system but I had to hot wire the compressor pump clutch to get it to run. It works and blows cold air when it is hot wired but won’t come on otherwise. Maybe the same wiring problem causing the A/C pump to not engage is causing my fan problem. Any ideas?

15

The electric fan is controlled by two things. If the coolant coming out of the rad is too hot, it should come on controlled by a switch in the water pump inlet elbow, just above where the lower radiator hose connects. With ignition on, you should be able to short the two connectors on that switch and the fan should come on. Otherwise, it rarely comes on at all because the coolant must be really hot to engage it, and with any luck your new rad is keeping it from getting that hot.

It’s also supposed to come on whenever the A/C compressor is engaged. In order that the signal from the switch in the inlet elbow doesn’t backfeed the A/C controls and vice versa, there’s a box full of diodes in the circuit. It looks like a blue relay, but there’s no relay inside, just a little circuit board with several diodes on it. Sometimes they get all corroded or whatnot and need to be replaced.

Obviously you need to correct whatever’s up with your A/C controls to get the compressor to engage as it should to see if the fan works with it.

16

Ok the fan problem was just the fuse. It now comes on when I hot wire the A/C compressor on. And also stayed on a minute or two so after I shut the car off and disconnected the A/C compressor. Now I’m trying to figure out the problem with the AC. When I 1st bought the car the compressor wire was disconnected and when I connected it the compressor clutch smoked and it didn’t turn so I know the electrical was working at that point but isn’t now since I replaced the compressor. I traced the wire from the compressor (blue/brown stripe) and it enters the firewall on the rh side. If I apply power to that wire back at the firewall it engages the compressor. So it seems to be something related to the interior controls

17

Is there a pressure sensor of some sort in the a/c line? I don’t see any. There is only the one wire tab on the back of the compressor that connects to the same wire wound (fuse of some sort) supplying power to the AC clutch that is also connected up to the firewall. Could I be missing a connection somewhere? I don’t understand what that compressor wire on the back does. It looks like the wire from the firewall connects to the same side of the fuse that goes to the compressor and the wire to the back of the compressor connects to the other side of the fuse.

18

I found there is a bunch of info on this post

so I will try the suggestions.

19

Your car is an '84. I believe that means it has the infamous 3-wire fuse arrangement. There is a sensor plugged into the back of the compressor that senses when it’s low on refrigerant; I believe it senses that things are getting too hot. All it does then is short a wire to ground. Attached to a bolt on the front of the compressor is a 3-wire fuse; one wire from the controls, one to the compressor clutch, and one to that sensor on the back of the compressor. When the sensor shorts its lead to ground, it blows the fuse, and that cuts power to the clutch. Have to buy a new 3-wire fuse when the system is recharged.

Later GM and hence Jaguar went to a different scheme with a sensor on the back that merely disconnected the compressor clutch. This was a pressure sensor I believe, not a temperature sensor like the first one – and it didn’t fit the same hole, the rear plate of the A-6 compressor was altered to accommodate it. But no fuses were involved; when the system was recharged, the clutch would engage.

20

ATTY Dallas"

  1. A bit of chiding. You would be severely hampered in your work if the law library was not available. Same for the Jaguar, You need documentation. Apologies.

  2. Check David Boger at everydayxj ffor NOS and good used parts. Moatly XJ, but some XJS and a lot of the stuff is shared.

  3. Study up on a relay’s logic. Intriguing. Easily sourced all over the planet. . 4 pin. most common.
    Two circuits. The trigger and the load. Many have a neat little diagram on top. Two pins each. Switch device to one leg of the trigger circuit. The other to ground.

Load circuit. One leg from constant 12 v source. the other to the load, in this case, the fan.

Switch on, relay kicks in 12 v goes to fan.

Why? Light load on the switch, lots of volts to the load…

Thermal switch. Bimetal? Heat closes the switch.
I’ve not tried it but, in theory, a heat gun or miladies hair dryer!!! Meter or test lamp across the pins. Apply the heat? Open or closes?

In my opinion, most any small fan sould do it…

Carl.