[xj-s] The Great Cooling Fan Switch Mystery... Do you know the answer


(AllanG) #1

I like a good mystery as much as the next guy but I find this
flipping ridiculous.

For a facelift XJS with 4.0L AJ6 engine, does anyone actually
know the temp that the thermostatic switch in the radiator
should turn on the electric fan? I have looked everywhere for
this info but no luck. My repair manual mentions that the
switch will turn the fan off at 90C (194F) but there is no
mention about when it will turn it on. This bugged me

So I started digging on the internet, first locating the
Jaguar part number DAC6794. I called around to all my go to
suppliers here in the US, Motorcars Ltd, Coventry West etc etc
but no-one has the part and hasn’t had it for a long time. So
I go to the Jag Classic Parts site in the UK and it says not
available, contact us. So I duly filled in the request form
and sent it off, receiving a reply the next day to say it’s
not available but they might have it in a month or two. Ok, so
I sent back an email asking for the temp spec of the switch.
The reply was, ‘‘sorry we don’t have that info’’

So I turned to some of the big chain parts suppliers, NAPA,
Autozone etc. They all show the switch on their sites with
prices ranging from $50-$100 but no specs. So I call all of
them and they say sorry part not available and they have no
info about the temp range!!

OK, so now I’m getting very curious and noting some of the
manufacturer names, I gave calls to Standard Motor Products,
BWD Intermotor and Wells Vehicle Electronics who all
purportedly manufacture the switch. I spoke with folks in
their tech departments and they ALL said the same
thing… Sorry part not available, sorry we don’t know
the spec and then they all said ‘‘we actually don’t make that
part it’s an OE’’. One particularly diligent chap at Standard
investigated for a few hours and then called me back to say
sorry no more info.

I find this very odd, I can’t think of any temp measuring
device in the car that doesn’t have a stated range, why would
this be any different?

I can take a guess on when it should come on but I want to
KNOW. I do know that my thermostat will start to open at 88C
(190F) and will be fully open by max 96C (207F), so I would
think that the fan would not come on till it got a bit higher
but when?

There have been many posts on this forum about high reading
temp gauges and cooling fans that either stay on all the time
or don’t appear to work at all, so it seems especially
important to know what’s what.

My fan works fine when I jump the switch so I know my circuit
is good. I haven’t been able to get the engine hotter than
about 96C (207F), which is a good thing , so I don’t expect
the fan come on but I want to know when it will.

Yes I know that I could take the switch out and try to suspend
it in some boiling antifreeze to test it but I shouldn’t have
to!!

Jovial rant over, enquiring minds want to know

Cheers,

Allan–
1994 XJS 4.0 2+2 Convertible 5 Speed Manual
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(vkv884j) #2

In reply to a message from AllanG sent Fri 12 Jul 2013:

I solved that problem with a $20 temperature controller off
Ebay. Set it from -50F to 200F and forget it. It even has
a nice digital readout. It isn’t weatherproof, but housed
in a plastic box it becomes so.–
The original message included these comments:

I like a good mystery as much as the next guy but I find this
flipping ridiculous.


vkv884j
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(Big Squatt) #3

In reply to a message from vkv884j sent Fri 12 Jul 2013:

everyone I have ever seen has the temp stamped on it.

Regardless of that get the lower temp units off ebay… They turn
on sooner and run longer after shutdown. Exactly what you want it
to do.

Jim–
87’ VDP (black), 86’ XJ-SC (grey), 88’ XJS sport convert
Fort Lauderdale, United States
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(AllanG) #4

In reply to a message from Big Squatt sent Fri 12 Jul 2013:

Jim,

Thanks, I already looked on the switch and nothing there.

I know that I have a wide variety of switches in the M22 x
1.5 size available, for me that’s not really the point.

It’s a small thing I know :)–
The original message included these comments:

everyone I have ever seen has the temp stamped on it.
Regardless of that get the lower temp units off ebay… They turn
on sooner and run longer after shutdown. Exactly what you want it
to do.


1994 XJS 4.0 2+2 Convertible 5 Speed Manual
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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(Big Squatt) #5

In reply to a message from AllanG sent Fri 12 Jul 2013:

Are you looking for the best option to replace the switch or just
curious about the temp on the original switch ?–
87’ VDP (black), 86’ XJ-SC (grey), 88’ XJS sport convert
Fort Lauderdale, United States
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(AllanG) #6

In reply to a message from Big Squatt sent Fri 12 Jul 2013:

The latter. I just find it so odd that no-one seems to
know.–
The original message included these comments:

Are you looking for the best option to replace the switch or just
curious about the temp on the original switch ?


1994 XJS 4.0 2+2 Convertible 5 Speed Manual
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(Daniel Cusick) #7

In reply to a message from AllanG sent Fri 12 Jul 2013:

IIRC sometime ago, close to ten years now, someone on this
list took theirs out and tested it. Somewhere around 215F
seems to stick in my mind. During that time a Porsche
number was being thrown around as a crossover. In 14 years
of ownership mine has been on only a few times when the
triple digits hit Illinois.–
Dan Cusick 1994 xjs 4.0L 1964 e-type FHC 1951 xk120 ots
Peru, Illinois, United States
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(AllanG) #8

In reply to a message from Dan Cusick sent Fri 12 Jul 2013:

Thank you Dan, 215F would seem reasonable. Still it would
be nice to know the spec.

Cheers,

Allan–
The original message included these comments:

IIRC sometime ago, close to ten years now, someone on this
list took theirs out and tested it. Somewhere around 215F
seems to stick in my mind. During that time a Porsche
number was being thrown around as a crossover. In 14 years
of ownership mine has been on only a few times when the
triple digits hit Illinois.


1994 XJS 4.0 2+2 Convertible 5 Speed Manual
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–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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(Steve) #9

In reply to a message from AllanG sent Fri 12 Jul 2013:

Allan:

I am not sure if there are differences in the operating
temperature for the I6 vs V12, but if this is of any help, the
OEM switch for the latter (EAC2510) has opening temperature
92�C; closing temperature is 82�C.

92�C coolant temp exiting the radiator, that is. The OEM T-
stats are 90�C.

As others have suggested, there are many aftermarket
alternatives with the correct thread size and different/lower/
opening and closing temperatures.

Hope this helps.
Best regards,
Steve–
The original message included these comments:

For a facelift XJS with 4.0L AJ6 engine, does anyone actually
know the temp that the thermostatic switch in the radiator
should turn on the electric fan? I have looked everywhere for
this info but no luck. My repair manual mentions that the
switch will turn the fan off at 90C (194F) but there is no
mention about when it will turn it on. This bugged me
So I started digging on the internet, first locating the
Jaguar part number DAC6794. I called around to all my go to


'95 XJS V12 6.0L, saphire/tan
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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(AllanG) #10

In reply to a message from sbobev sent Sat 13 Jul 2013:

Thanks Steve,

That is interesting. I’m guessing there must be significant
differences between the V12 and AJ6 engines. Some AJ6 owners
report that their switch goes on at around 215F and off around
195F. It sounds like the the purpose of the V12 switch is to
help prevent the coolant from going out of range whereas for
the AJ6 it seems that the purpose of the switch is to help
bring the temps back into range if they exceed the range by a
certain amount?

On AJ6 cars the switch is mounted at the top left of the
radiator which also supports that theory. I’m wondering if
there is a significant difference in the radiator design
between the two engines?

Cheers,

Allan–
The original message included these comments:

I am not sure if there are differences in the operating
temperature for the I6 vs V12, but if this is of any help, the
OEM switch for the latter (EAC2510) has opening temperature
92�C; closing temperature is 82�C.
92�C coolant temp exiting the radiator, that is. The OEM T-
stats are 90�C.


1994 XJS 4.0 2+2 Convertible 5 Speed Manual
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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(jdere) #11

In reply to a message from AllanG sent Fri 12 Jul 2013:

Hi Allan,
I’m still having problems with the fan radiator circuit.
I took out the thermostat switch and tested it several times
in a hot water pot.
The circuit closed every time at about 190 degrees farenheit.
The switch appears to be original and my car is a 1989 XJS.–
The original message included these comments:

I can take a guess on when it should come on but I want to
KNOW. I do know that my thermostat will start to open at 88C
(190F) and will be fully open by max 96C (207F), so I would
think that the fan would not come on till it got a bit higher
but when?
There have been many posts on this forum about high reading
temp gauges and cooling fans that either stay on all the time
or don’t appear to work at all, so it seems especially
important to know what’s what.
My fan works fine when I jump the switch so I know my circuit
is good. I haven’t been able to get the engine hotter than


jdere
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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(Veekay) #12

I know this is an old thread, but since I have my sensor out, I can answer this question definitively.

The sensor is stamped with “F96/91C” which probably means the switch is set to activate at 196F or 91C.

It is the OEM made in the UK by Elmwood. DAC6794 is indeed stamped in as well.

Also stamped is 3000-923-10 also “4895”


#13

Normally on a thermoswitch 96/91C would indicate on at 96 off at 91.