[xj40] no warm air to defroster outlets

Henge · October 15, 2014, 11:53pm

I have owned the wonderful 1994 xj40 for 10 months, I don’t
have a owners manual, but I know the heater worked better
in the winter and I have tried all the buttons and switches
and I can’t figure out if I have a problem or not.
I do get warm air to the floor vents for the front seats
and I get warm are to the back seats. The temperature
control knob does change the temperature of the air coming
out of those vents. When changing to defrost and not
defrost it sounds like the solenoid or linkage is moving,
but it doesn’t close off flow when I think it should and
always blows cold air to the windscreen. the face vents
always blows cold air, but I can close them. I am confused
of what I read, does my car have these pesky electric flap
controllers that people talk about or do I have other
issues?–
Henge
Waynesboro/PA, United States
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Bryan_N · October 16, 2014, 10:18am

In reply to a message from Henge sent Wed 15 Oct 2014:

It sounds as if you have two problems.

the vacuum operated demist/defrost vent flaps under the
windshield are stuck open. That could be due to a
disconnected vacuum line or, more probably, the mechanical
linkage has failed. To fix or replace a broken
demist/defrost vent flap the dash has to be removed.
the upper electrically operated blend flap (UBF) in the
climate control unit (CCU) is stuck in the fully cold
position. Sometimes that can be released by giving the UBF
motor/gearbox unit (upper right side of the CCU) a series of
whacks with a metal rod whilst cycling the temperature
control knob from hot to cold and back again whilst the
system is switched on and the engine is up to normal
operating temperature. Otherwise you will need to remove the
UBF motor/gearbox unit and manually rotate the shaft of the
flap with a screwdriver inserted in to the slot on the end
of the shaft.

I will send a separate post describing the function of the
the HVAC controls since there is not enough room left on
this post.–
The original message included these comments:

have a owners manual, but I know the heater worked better
in the winter and I have tried all the buttons and switches
and I can’t figure out if I have a problem or not.
I do get warm air to the floor vents for the front seats
and I get warm are to the back seats. The temperature
control knob does change the temperature of the air coming
out of those vents. When changing to defrost and not
defrost it sounds like the solenoid or linkage is moving,
but it doesn’t close off flow when I think it should and
always blows cold air to the windscreen. the face vents

–
Bryan N, now Jag-less, but fun while it lasted.
Cambridgeshire, United Kingdom
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Bryan_N · October 16, 2014, 10:33am

In reply to a message from Henge sent Wed 15 Oct 2014:

As promised - see below:-

FAN (BLOWERS) CONTROL

OFF - The system is not operational. Power is off, but a
signal is sent to the climate control ECU to ensure that the
re-circulation (blower intake) flaps are closed to prevent
outside air from entering the car.
LOW � In automatic mode, the climate control ECU maintains
blower speed within a range of low speeds, depending on the
temperature requirement, fan speed being gradually reduced
as the target temperature is achieved
MED � In automatic mode, the climate control ECU controls
the full range of blower speeds, depending on the
temperature requirement, fan speed being gradually reduced
as the target temperature is achieved .
HIGH - The blowers run at high speed only.
DEF - The blowers run at high speed - full air flow at �full
heat� is directed to the windshield.
[NOTE: When heat is required, the blowers will not operate
(unless the fan speed is set to �DEFROST�) if the engine
coolant temperature is below 85� F]

TEMPERATURE CONTROL

MANUAL button NOT selected � The climate control ECU
maintains selected IN-CAR temperature within a range of 63�
to 86�F
MANUAL button IS selected) - VENT outlet temperature is
maintained at the level selected by the driver.
[NOTE the differentiation between �In-car temperature� and
�Vent outlet temperature�]

MANUAL BUTTON

Not selected - AUTO - The system is under ECU control and
automatically maintains the selected IN-CAR temperature.
Selected - MANUAL - The system sensors are overridden and
the selected temperature is provided at the VENT outlets.

DEMIST BUTTON

When selected / illuminated - Windshield demisting is
provided but with NO change to air temperature.

AIR CONDITIONING BUTTONS

MAX � Provides maximum cooling, overriding all other
functions except �DEFROST� and �OFF�. It is a manual setting
which automatically sets the system to the highest available
fan speed and gives the coldest air from the vents at the
maximum de-humidifying setting
ON � when selected cancels the MAX button and provides air
conditioning at the minimum de-humidifying setting.

FACE VENTS SLIDER CONTROL

The outlet air temperature of the two SIDE fascia vents can
be controlled by the sliding bar (but only as a reduction
to its temperature in relation to the temperature of the air
at the foot well vents). Full up decreases side vent air
temperature; full down increases side vent air temperature
up to the temperature of the air from the foot well vents.

RECIRCULATION BUTTON

When selected, shuts off the outside air intakes at the blowers

HEATED FRONT SCREEN BUTTON [Where fitted]

Operates front screen heater for up to six minutes when
selected manually and is automatically switched on when
�DEFROST� is selected on the fan speed control.

I will send you further information on systematically
checking the operation of the HVAC system in another post–
The original message included these comments:

I have owned the wonderful 1994 xj40 for 10 months, I don’t
have a owners manual, but I know the heater worked better

–
Bryan N, now Jag-less, but fun while it lasted.
Cambridgeshire, United Kingdom
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Bryan_N · October 16, 2014, 10:37am

In reply to a message from Henge sent Wed 15 Oct 2014:

Here’s the HVAC test on the '93 / '94 model XJ40.

If you follow this and report back the precise results of
checks 1 to 12 we will be better able to analyse what is
wrong with the system on your car.

After determining that BOTH blower fans are operating
(by pulling the individual L & R B4 fuses one at a time) and
with the engine up to normal operating temperature, set the
temperature control knob on the panel to ‘Full Cool’, the slider
control to �cold� and select the ‘Manual’ button. Then set the
fan speed on ‘Defrost’ (nothing else selected)

You should get:-

Hot air at full volume out of the demist vents
Some air out of the side face vents
NO air out of the centre face vents
NO air out of the footwell vents

Turn the fan speed control to ‘High’ and select the �On� A/C
button.

After a delay of, perhaps, 45 seconds, you should get:-
5) NO air out of the demist vents
6) Cold air out of the side face vents
7) Cold air out of the centre face vents
8) Cold air out of the footwell vents

[You can increase the effect of the air conditioning by using
the �Max� button which will override all other functions except
�Defrost� and �Off� and put the fan speed to �High� if not
already there]

Press the �On� button, turn the temperature control knob to
‘Full Heat’
and the slider control to �hot�.

After a delay of, perhaps, 45 seconds, you should get:-
9) NO air out of the demist vents
10) Hot air out of the side face vents
11) NO air out of the centre face vents
12) Hot air out of the footwell vents.

NOTE:

In automatic mode (‘Manual’ not selected) the ECU varies the
fan speed on ‘Low’ and ‘Medium’ only but not on ‘High’ or
‘Defrost’.–
The original message included these comments:

I have owned the wonderful 1994 xj40 for 10 months, I don’t
have a owners manual, but I know the heater worked better
in the winter and I have tried all the buttons and switches
and I can’t figure out if I have a problem or not.

–
Bryan N, now Jag-less, but fun while it lasted.
Cambridgeshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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John_Quilter · October 16, 2014, 11:45pm

In reply to a message from Henge sent Wed 15 Oct 2014:

Can’t imagine figuring out all the operational and
maintenance features of a Jaguar without an owner’s manual.
They are often available on E Bay.–
The original message included these comments:

I have owned the wonderful 1994 xj40 for 10 months, I don’t
have a owners manual, but I know the heater worked better

–
John Quilter 1965 3.8S, 1951 MGTD, 1960 Morris ,1990 XJ6
Eugene, Oregon, United States
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Bryan_N · October 21, 2014, 6:15pm

In reply to a message from Henge sent Wed 15 Oct 2014:

Well, did you get it sorted?–
The original message included these comments:

I have owned the wonderful 1994 xj40 for 10 months, I don’t
have a owners manual, but I know the heater worked better
in the winter and I have tried all the buttons and switches
and I can’t figure out if I have a problem or not.

–
Bryan N, now Jag-less, but fun while it lasted.
Cambridgeshire, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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Henge · November 3, 2014, 2:21am

In reply to a message from Bryan N sent Thu 16 Oct 2014:

I got the knee bolster off today, smacked the housing but
that didn’t fix it. I guess I have to figure out how to
get to the upper flap control. Henge–
Henge
Waynesboro/PA, United States
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Henge · November 4, 2014, 1:12am

In reply to a message from Bryan N sent Thu 16 Oct 2014:

Thanks Bryan for the reply here are my findings.
First when I push the manual button the light comes on it,
but when I go to ‘‘Defrost’’ the light in the manual button
goes off.
The answer to #1 I have cold air there
The answer to #2 I have cold air there
The answer to #3 I have air coming out the face vents if I
have the rolling flow control knob open or allowing it.
The answer to #4. I don’t have air coming out of the floor
vents.
The answer to #5, I do have air coming out of the defroster
grill
The answer to #6, 7, and 8 cold air out of each
The answer to #9,i do have air coming out of the demist
vents
The answer to #10, I don’t have hot air out of the side
face vents
The answer to #11 I do have air coming out of the centre
face vents as long as I have the rolling knob to allow it.
The answer to #12, yes I have hot air out of the footwell
vents.–
Henge
Waynesboro/PA, United States
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Bryan_N · November 4, 2014, 9:24am

In reply to a message from Henge sent Mon 3 Nov 2014:

OK, here is my analysis of your results:-

Upper blend flap in the CCU stuck in full cold position
As in 1)
The centre face vents should only be open (by vacuum)
when A/C is selected, so it can be deduced that the centre
vent flap mechanism is broken and the vents are stuck in the
fully open position. Not a real problem if you can close off
the outlet with the thumb wheel when you do not want hot air
(if you ever get any!) out of the centre vents.
Good - the lower blend flap in the CCU is closing as it
should when ‘defrost’ is selected.
That confirms that the demist/defrost vacuum operated
vent flaps are stuck in the open position whereas they are
ordinarily held closed by vacuum until those features are
selected.
6), 7), 8) Good, as it should be
As in 5) above
As in 1) above
As in 3) above
Good - that indicates that the lower blend flap in the
CCU is working OK.

As I mentioned previously, if the demist/defrost vents are
stuck open because of a mechanical failure, the only
solution is to remove the dash to effect a repair. However,
first check that the GREEN vacuum line is connected and, if
you can temporarily disconnect it from the vacuum valve
block and apply a vacuum manually, check to see if it closes
when that vacuum is applied.

If the upper blend flap cannot be ‘unstuck’ by whacking its
motor/gearbox unit with a metal rod whilst cycling the
temperature control from hot to cold and vice-versa, you
have no alternative but to remove that unit and ‘unstick’
the blend flap manually by turning the shaft with a
screwdriver in the slotted end.–
The original message included these comments:

Thanks Bryan for the reply here are my findings.

–
Bryan N, now Jag-less, but fun while it lasted.
Cambridgeshire, United Kingdom
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Henge · November 5, 2014, 3:18am

In reply to a message from Bryan N sent Tue 4 Nov 2014:

Thanks very much for your timely reply. Any hints on
getting to the top blend motor. Pictures I have seen in
the forum looks easy to see or get to the bottom one. It
isn’t clear to me where the top one is and how to get to
it. I take it taking the top dash off is a large task?–
Henge
Waynesboro/PA, United States
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Bryan_N · November 5, 2014, 8:45am

In reply to a message from Henge sent Tue 4 Nov 2014:

I’ve sent via PM a zip folder with the information that you
need to do that job. Quite a task for sure.–
The original message included these comments:

Thanks very much for your timely reply. Any hints on
getting to the top blend motor. Pictures I have seen in
the forum looks easy to see or get to the bottom one. It
isn’t clear to me where the top one is and how to get to
it. I take it taking the top dash off is a large task?

–
Bryan N, now Jag-less, but fun while it lasted.
Cambridgeshire, United Kingdom
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Henge · November 27, 2014, 1:32pm

In reply to a message from Bryan N sent Thu 16 Oct 2014:

I have heat! First of all a very big thank you to Bryan N
who took me under his wing and continued to help me fix my
car. Sure enough the driver side demist flap/door broke
off at the hinge on the actuator end and fell down into the
CCU, thus not allowing the upper temp flap to move. I can’t
seem to locate one, so I used some very special glue and
hope it will hold. Just in case it fails again, I made and
installed a ‘‘catch net’’ so the flap can’t fall into the CCU
again, and I will still have heat. Again thanks Bryan, you
were much better than the Haynes manuals and CD’s I
purchased. Now on to other issues, like a fallen headliner,
and a loud knocking noise when hitting sharp bumps, but at
least I can enjoy our ride again now that the cold season
has hit.–
The original message included these comments:

Here’s the HVAC test on the '93 / '94 model XJ40.

–
Henge
Waynesboro/PA, United States
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Jaguarpete · November 27, 2014, 2:39pm

In reply to a message from Henge sent Thu 27 Nov 2014:

When you do your headliner, plan on 3 hours to remove the
headboard and all day to reinstall it. I’ve recently done
two of them – my 1988 daily driver as SWMBO’s 1989 – both
with sun roofs. I used doubleknit sweatshirt material I
bought from Joann’s Fabrics and glued it onto the molded
fiberglass headboard with 3M No 77 spray adhesive with the
‘fuzzy’ side out.–
The original message included these comments:

purchased. Now on to other issues, like a fallen headliner,
and a loud knocking noise when hitting sharp bumps, but at
least I can enjoy our ride again now that the cold season
has hit.

–
Pete Peterson 70E(193K) XJ40s(88-270K,89-97K, 94-122K)
Severna Park, Maryland, United States
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Bullydog · November 27, 2014, 4:22pm

In reply to a message from Jaguarpete sent Thu 27 Nov 2014:

Hey Pete
Do you mind detailing the procedure on how you removed it
from the car and got it back in without damage?
I know Don B has a great tutorial about this but always
willing to listen to others experience doing it.–
Bullydog
New York, United States
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Jaguarpete · November 28, 2014, 5:55pm

In reply to a message from Bullydog sent Thu 27 Nov 2014:

The workshop manual on CD has an excellent detailed
procedure. You’ll have to take out a good part of the
interior – including the steering wheel, inner passenger
door trim, center console, and underdash trim on the
passenger side, seats laid back – to allow extraction. The
width of the fiberglass headboard is about a half-inch
shorter than the diagonal measurement of the front door.
Once you have the headboard loose, you’ll jockey the rear
corner of the headboard out the passenger rear door, which
allows the cut-out for the overhead console to straddle the
B pillar (both doors open) and that will allow the headboard
to line up diagonally with the passenger door.
There are a number of small cut-outs on the sides of the
headboard to mind, but it will come out (and go back in)
without too much fiddling. The formed fiberglass headboard
is somewhat fragile and could bend or tear if you don’t
handle it gently. There are 6 small metal tabs that hold
the headboard in position. You’ll need to bend them down a
bit to release the board.–
The original message included these comments:

Do you mind detailing the procedure on how you removed it
from the car and got it back in without damage?
I know Don B has a great tutorial about this but always
willing to listen to others experience doing it.

–
Pete Peterson 70E(193K) XJ40s(88-270K,89-97K, 94-122K)
Severna Park, Maryland, United States
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