[xj-s] Climate Control

Hi all,
My Climate Control is not working properly.
When it is on the manual setting I can get both hot air and really cold
air when I change the temp. control.
It’s when I switch to auto things go wrong.
The air blown out is hot. It doesn’t matter what I set the temp. control
to, it stays hot - even on hot sunny days.
Is the temperature sensor in the car broken? If so, where is it and how
do I fix it?
Can anyone help?
Thanks,
Pat
'87 XJ-S 3.6

Hello All:

I’ve recently purchased my first XJ-S - an '88 5.3 coupe. Car’s in nice
shape w/very low mileage. Previous Jags included a 1973 Series 1 SWB XJ12
and a 1982 XJ6. I haven’t had the XJ12 for a number of years but,
the XJ-S brings back fond memories of that car. The V-12 feel is very
similar to that early sedan. The XJ-S, of course, is fantastic in its own
way!

So, what’s the problem? Well, I have a rather confused climate control
system. It wants to blow cold air from the center dash vents and hot air
from the lower vents - at the same time. Given that the outside temp this
morning was about 8 degrees F, I’m guessing this isn’t quite right… FWIW,
the defrost setting also blows cold air (from the proper upper dash vents).

I’m hunting down a proper copy of the ROM and have also found a Delanair III
troubleshooting book. Unfortunately, I don’t yet have either of them in my
possession. Any thoughts on troubleshooting this one?
Thanks.

Regards,
Odysseus

Odysseus Marcopolus, 88 XJ-S 5.3
@Odysseus_Marcopolus
Bucks County, Pennsylvania, US

Odysseus,

I believe that’s the way it’s supposed to work. Theory is that the air near
one’s legs and feet are supposed to be
warmer than upper body and head.

Ed Sowell
76 XJ-S

Thanks Ed except, in this scenario, we’re not talking about a slight
difference in temp between the dash and floor vents.

Rather, the air coming out of the center vents is very cold (as in a/c
refrigerated air) while the air coming out down below is heated (as it
should be given the outside temp here in the dead of winter).

The problem seems to be that the climate control wants to run in both
a/c and heat “modes” at the same time.

Regards,
Odysseus

Odysseus Marcopolus, 88 XJ-S 5.3
@Odysseus_Marcopolus
Bucks County, Pennsylvania, US

“Edward F. Sowell” wrote:>

Odysseus,

I believe that’s the way it’s supposed to work. Theory is that the air near
one’s legs and feet are supposed to be
warmer than upper body and head.

Ed Sowell
76 XJ-S

Thanks Ed except, in this scenario, we’re not talking about a slight
difference in temp between the dash and floor vents.

Rather, the air coming out of the center dash vents is very cold (as in a/c
refrigerated air) while the air coming out down below is heated (as it
should be given the outside temp here in the dead of winter).

The problem seems to be that the climate control wants to run in both
a/c and heat “modes” at the same time.

Regards,
Odysseus

Odysseus Marcopolus, 88 XJ-S 5.3
@Odysseus_Marcopolus
Bucks County, Pennsylvania, US

“Edward F. Sowell” wrote:

Odysseus,

I believe that’s the way it’s supposed to work. Theory is that the air
near> one’s legs and feet are supposed to be
warmer than upper body and head.

Ed Sowell
76 XJ-S

Hi Scott,
Did you replace the Darlingtons?
http://www.mph150.freeserve.co.uk/acblower.htm
for wiring diagram and info.
ATB Alan Baker '88 3.6

Climate Control fans I have repaired both following the instructions on the Jag-Lovers
web> site and Mark Barkers web site, both circuits appeared to be in a state of
disrepair, the glass diodes had definitely disintegrated.
Since then, I now have both fans working on full, but no other speeds and I
still have to pull the temp switch to get them to start.
Have I done something as simple as a diode around the wrong way?

Is there a way to override the automatic climate control on my '86
Cabriolet? According to the owners manual there is no manual
option, it is always automatic.

The A/C compressor does not work. I drive it with the tops off,
but the air flowing thought the vents feels heated. Is there a way
to draw clean air from outside the car? It feels like the air
flowing in is coming through the engine compartment; hence the hot
air. Driving it on Saturday night, it was 70 degrees outside and
the airflow was definitely heated.–
KBininger
White Plains, NY, United States
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In reply to a message from KBininger sent Mon 7 Jul 2003:

There is no way to override the climate control. At best, make sure
the heater valve is off to make the heater hoses are as cool as
they can get under the hood of an XJS. The best way to cure this
problem is to fix the AC!–
the Pro from Dover
washington d.c., United States
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In reply to a message from the Pro from Dover sent Tue 8 Jul 2003:

Exactly.
As ‘‘The Pro from Dover’’ says , ‘‘FIX THE A/C’’
When I recently bought my '92 XJS 90K mls, the compressors was
goosed. The car came with another used compressor so it just needed
changing and a new fan belt.
When I drove it home (500 mls) the weather was hot, any air coming
through the vents was hotter, the window was down and I was boiling
in the body and the legs were roasting and I could’nt hear the
music for the windrush thru the open window.
Today I got the car out of the garage after having the compressor
fitted, the gas changed from R12 to R134 and paying �234 PGB.
The mechanic who knows stated that there was either cold air from
the A/C or hot air from the engine. Any air coming into the cockpit
was a mixture of these two. No outside air route at all.
Now the car is a wonder to drive and I can hear the music again
without the open window and air rush.
Hope this helps–
The original message included these comments:

There is no way to override the climate control. At best, make sure
problem is to fix the AC!
the Pro from Dover


Brian XJ(40) + XJS
Lancashire, United Kingdom
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Hello, KBininger. You wrote, “I drive it with the tops off,
but the air flowing thought the vents feels heated. Is there a way
to draw clean air from outside the car?.” I haven’t done it yet, but some
recent posts indicate that if your a/c is not working, there is a good
possibility the vacuum to shut the heater control valve (if yours is still
working and not frozen in the “open position”) is not operating and is
allowing heated water to pass through the heater core. The suggestion was
to run a vacuum line from the rear of the right manifold and “T” it into the
heater control vacuum line you will get ambient temp air into the car,
unless you select “defrost”, which will dump the vacuum and you’ll get warm
air for demisitng. As soon as I get the new bellows kit installed on the
boat’s outdrive, I’ll get to it and post results.

Jim Johnson
XJ-S (built 03/87), V12 (Lucas CEI), TH400 (w/B&M), Dana 2.87
Annapolis, Maryland

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In reply to a message from KBininger sent Mon 7 Jul 2003:

The best solution must be to get your air con system working as
designed but that could cost a fortune, depending on what is wrong
and whether anyone can find the problem. It may be more than your
compressor. Somebody advised me that there is a simple modification
which can be made to the Jaguar saloons to enable fresh air to flow
into the cabin. But I haven’t been able to find the details or
ascertain whether the method - modifications to electronic
circuitry, I think - would apply to the XJ-S.

As I see it, there are at least three main sub-systems which work
together on air-con and almost non-existent ambient ventilation on
the XJ-S: (a) the refrigeration ‘plumbing’ including the
compressor, condensor, evaporator, expansion valve and receiver-
drier, which should make the evaporator freezing cold inside the
car if everything is working properly. (b) the tubes, vents, fans
and electro-mechanical components which should work to deliver air
into the cabin, breezing over the evaporator for cold air, and/or
the heater matrix for warm air. And © the arguably over-complex
XJ-S air-con electronics which control and monitor (a) and (b). On
many cars you can get a good flow of ambient air with or without
the air-con being turned on, but not with the XJ-S - appalling
design in my opinion.

My last-ditch approach, if and when it comes to it, and all else
has failed, will be to disable (a), and replace © with manual
switches or whatever. Part of the job of the XJ-S electronics is to
monitor cabin temperature (so-called climate control) and turn the
compressor/heater on and off to arrive at the required, blended
temperature. If you have disabled (a) it strikes me you only have
to worry about flap control and the blowers before disabling ©.
With the system working as designed, the electronics act to control
servo valves which direct vacuum feeds to vacuum-driven ‘motors’ on
each flap. Without the electronics ©, the vacuum servo devices
won’t work, so I envisage either (1) over-riding the servo motors
which ‘distribute’ the vacuum or (2) fixing manual cables to the
flaps or (3) semi-jamming the flaps in a fixed position to arrive
at the required level of air flow. I would then control whether hot
water flowed into the heater matrix via a simple tap under the
bonnet, with another tap under the dashboard for some control over
heating level. The blowers (fans) would be controlled by direct
power feeds. My objective will be to ensure that sufficient air
flows from the bottom of the XJ-S windscreen into the cabin, just
like most cars, for ambient air in summer and various levels of
heated air in winter.

Given that the incoming air doesn�t go through the engine bay, I
don�t see how engine temperature is much of a threat.

I just hope I never have to do it.

Regards
George–
The original message included these comments:

Is there a way to override the automatic climate control on my '86
flowing in is coming through the engine compartment; hence the hot
air. Driving it on Saturday night, it was 70 degrees outside and
the airflow was definitely heated.


1989 XJ-S 3.6
London, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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In reply to a message from KBininger sent Mon 7 Jul 2003:

The original message included these comments:

Is there a way to override the automatic climate control on my '86
flowing in is coming through the engine compartment; hence the hot
air. Driving it on Saturday night, it was 70 degrees outside and
the airflow was definitely heated

George Bray wrote:

The best solution must be to get your air con system working as
designed but that could cost a fortune, depending on what is wrong
and whether anyone can find the problem. It may be more than your
compressor. Somebody advised me that there is a simple modification
which can be made to the Jaguar saloons to enable fresh air to flow
into the cabin. But I haven’t been able to find the details or
ascertain whether the method - modifications to electronic
circuitry, I think - would apply to the XJ-S.

Hi George,
The fresh-air mods for the XJ-S are covered in Kirby’s Book starting at
page 522, September 15, 2002 current version. I modified my '88 convertible
for the fresh air option since having the A\C compressor run full time
struck me as idiotic; especially in the dead of winter.

Dave Osborne
88 H&E XJ-S (PURR)
Carson City, Nevada

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In reply to a message from David Osborne sent Wed 9 Jul 2003:

David

Thank you for pointing out that the fresh air moifications are
described in ‘The Book’, at least for cars where the air
con ‘computer’ and most of the other electronics are still working
OK. I’d looked at the general air-con section but didn’t realise
there was a separate section on modifications. I agree that it
seems better to have the compressor turned off for the winter.

Regards
George–
1989 XJ-S 3.6
London, United Kingdom
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Hello, KBininger. You wrote, “I drive it with the tops off,
but the air flowing thought the vents feels heated. Is there a way
to draw clean air from outside the car?.” Latest post: I had previously
installed an aftermarket, plastic heater control valve to replace the
rusted, frozen OEM. The new valve’s vacuum barb is for 1/4" vacuum hose vs
the OEM of about 3/16" and I had installed a splice to join the climate
control 3/16" vacuum hose and the 1/4" control valve. I must have use
either 7.5mm or 5/16" instead of 1/4" and that resulted in a vacuum leak at
the valve, allowing heated water to pass through the heater matrix even with
the temp control knob turned to 65 degrees. When I replaced the hose splice
with 1/4" hose, the heated air from the vents stopped and I now have ambient
temp air from left, right, center and footwell vents. With the sunroof out,
windows open, and blower set to LOW, the car is now comfortable in traffic
even into the 90’s.

Jim Johnson
XJ-S (built 03/87), V12 (Lucas CEI), TH400 (w/B&M), Dana 2.87
Annapolis, Maryland

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My local mechanic and I have given up on solving a few issues with
the heating/air conditioning system on my '94 convertible. We have
the ROM, and have researched the ‘‘book’’, but the flaps seem
commited to defrosting, and we need help. The closest dealer to me
is in Portland Oregon, and the service manager there seems to know
less about the problem than I do, which is pretty scary. Does
anyone know who I could turn to in the Portland area who is
familiar with this climate control system? Most of the year I am
happy with the convertible top being all the climate control a boy
could wish for, but with the rain lately, I need the thing to work.–
'94 XJ-S 4.0 Convertible
Cannon Beach Oregon, United States
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In reply to a message from Capper sent Fri 13 Jan 2006:

Hi

You say the ‘‘flaps seem committed to defrosting’’. This can
only have a few causes:

(a) one or more flaps are siezed on their ‘hinges’ and need
freeing-off and lubricating.
(b) one or more flaps are not reciving a vacuum (or perhaps
electric motor for a 94 model) feed to drive the ‘motor’ to
move the flap(s). Check that any vacuum pipes have not come
loose.
© the vacuum ‘distributor’ is faulty, even if a vacuum
flow of air is present up to the ‘distrbutor’.
(d) (less likely) the air con ECU is faulty and not ‘‘telling
the vacuum distributor what to do’’.

I suggest that access is a much greater problem than
diagnosis here. You may need to remove the entire
facia/dashboard if you can’t get access to the relevant
flaps - at least the ends of the flaps) from the sides, if
it’s not something simple like a loose vacuum pipe in a
convenient location.

Regards
George–
The original message included these comments:

My local mechanic and I have given up on solving a few issues with
the heating/air conditioning system on my '94 convertible. We have
the ROM, and have researched the ‘‘book’’, but the flaps seem
commited to defrosting, and we need help. The closest dealer to me


1989 XJ-S 3.6
London, United Kingdom
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In reply to a message from Capper sent Fri 13 Jan 2006:

Only other thing I can think it could be is the ‘‘DEMIST’’ circuit is
staying energized because of a faulty switch.–
Royce Robertson Upgraded to a 1995 XJ-S 4.0 AJ16
Elkford, British Columbia, Canada
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I just purchased a 1992 XJS V12. The climate control does not blow
hot air. Any ideas where I should start troubleshooting this
problem?–
Prodriller
Evansville, IN, United States
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In reply to a message from Prodriller sent Sun 27 Dec 2009:

First thing you want to do is make sure your coolant level
is correct. Look to see if the water control valve on the
firewall is moving. Put a piece of tubing on it and suck on
it to see if the lever moves freely. If not, you need to
change it out. If it moves freely you probably have a vacuum
manifold problem under the dash or clog along the way.–
The original message included these comments:

I just purchased a 1992 XJS V12. The climate control does not blow
hot air. Any ideas where I should start troubleshooting this
problem?


equiprx
Pacifica, CA, United States
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In reply to a message from equiprx sent Sun 27 Dec 2009:

The coolant valve moves freely. I felt no suction in the supply
line. Where is the source of the vacuum located under the dashboard.–
Prodriller
Evansville, IN, United States
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