[xj40] Air Conditioning blowing hot air

The air conditioner is blowing hot air, I have it on max cooling to
no success. The blower is working, it just seems to be blowing hot
air. Anyone have any advice?–
Tom Craven
East Fremantle, Australia
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Hi Tom,

What model year is your car? The first thing to check is whether or
not the compressor clutch is engaging. If you turn the engine off,
open the bonnet, turn the blower switch to Low with the Temp control in
coldest setting, and turn the key to the run position without starting
the engine. In a quiet garage, you should hear a sharp click from the
front of the engine as the compressor clutch engages. You can also
look at the front-center of the compressor pulley area to see if that
is turning when the motor is running and the switches set as above.

Let us know what you find in that test, and we can take it from there.

George Balthrop, Clifton, VA USA
85 & 89 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Cravo cravth08@student.aquinas.wa.edu.au

The air conditioner is blowing hot air, I have it on max cooling to
no success. The blower is working, it just seems to be blowing hot
air. Anyone have any advice?


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G’Day Tom, what a bugger in this weather (37C today),. If there is not
enough gas in the system then the low pressure switch will stop the clutch
from energizing.
Try to see (hear) the clutch coming on when you turn the a/c on. If not
short the said switch out and try again. If it now comes in then you are low
on gas.
All the best,
Brian.
@BrianDD
1990 XJ40 Sport

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In reply to a message from gbalthropxjs@aol.com sent Sat 2 Feb 2008:

Thanks, for the help. The car is an 88 model, I ran the test
and the clutch is engaging the air just doesnt seem to be
cold at all.–
Tom Craven
East Fremantle, Australia
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Have you checked that the blend flap is closing off the heater matrix? As I
remember the heater is always on and the hot air from the heating matrix is
held back by the blends flap. If the flap jams or stops working then the hot
air will overwhelm the cold air from the air con.-----Original Message-----
From: owner-xj40@jag-lovers.org [mailto:owner-xj40@jag-lovers.org] On Behalf
Of Cravo
Sent: Saturday, February 02, 2008 8:13 PM
To: xj40@jag-lovers.org
Subject: Re: [xj40] Air Conditioning blowing hot air

In reply to a message from gbalthropxjs@aol.com sent Sat 2 Feb 2008:

Thanks, for the help. The car is an 88 model, I ran the test
and the clutch is engaging the air just doesnt seem to be
cold at all.

Tom Craven
East Fremantle, Australia
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !

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In reply to a message from Cravo sent Sun 3 Feb 2008:

Tom,

This subject has been covered extensively on the forum in
the past. Here is an extract from the XJ40 archives of a
simple test you can do to determine if the system is
functioning correctly:-

The system relies on electrically operated
blend flaps in the climate control unit (CCU) to adjust the
temperature of the air exiting the vents and vacuum operated
duct flaps to direct the air through the chosen vents.

Sometimes a CCU blend flap gets stuck through lack of use
and the system cannot control the temperature exiting the vents.

You may be able to determine where the problem lies by
conducting this simple initial test :-

With the engine up to normal operating temperature, set the
temperature control knob on the panel to ‘Full Cool’ in
‘Manual’ mode with the fan speed on ‘Defrost’ (nothing else
selected)

You should get:-

  1. Hot air at full volume out of the DEMIST vents
  2. Some air out of the SIDE face vents
  3. NO air out of the CENTRE face vents
  4. NO air out of the FOOT WELL vents

Turn the fan speed control to ‘High’.

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 FOOT WELL vents

Turn the temperature control knob to ‘Full Heat’

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 FOOT WELL vents.

NOTES:

  • The ‘45 seconds’ delay is to allow the ECU / system to
    react to the new selection - and to avoid ‘hunting’.
  • You can REDUCE the temperature exiting the face level
    vents in relation to that exiting the footwell vents by
    moving the slider control from ‘hot’ (temperatures the same)
    to cold (face level cooler)
  • You can introduce demisting by selecting the ‘AIR’ (or
    ‘Screen’) button on the panel
  • You can alter the dehumidifying effect of the A/C by using
    the ‘raindrops’ buttons or cut out the A/C compressor
    completely by selecting ‘ECON’
  • In ‘Auto’ mode (not ‘Manual’) the ECU varies the fan speed
    on ‘Low’ and ‘Medium’ only but not on ‘High’ or ‘Defrost’.

Post the results of 1 to 12.

From your description, it sounds as if the blend flaps in
the CCU are stuck in the ‘full heat’ position. ALL of the
air entering the CCU is at ambient temperature (refrigerated
if the A/C is working) by passing through the A/C
evaporator. If the blend flaps are in the ‘full cool’
position, that refrigerated air will by-pass the heater
matrix and exit the CCU as cold air out of the cabin vents.
Normally you need to select ‘heat’ for those blend flaps to
move in to a position to divert the cold air through the
heater matrix to warm it up - but if one or both flaps is
stuck in the ‘full heat’ position, ALL the air will be
diverted / heated, despite having the A/C selected.–
The original message included these comments:
Thanks, for the help. The car is an 88 model, I ran the test
and the clutch is engaging the air just doesnt seem to be
cold at all.


Bryan N, '91 Sovereign 4.0 L, RHD (exiled in US)
Cambridgeshire, United Kingdom
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In reply to a message from Bryan N sent Sun 3 Feb 2008:

Tom,

Just to correct some sloppy authoring in my last post.

‘‘ALL of the air entering the CCU is at ambient temperature
and all of that air passes through the A/C evaporator as it
enters the CCU where it is refrigerated if the A/C is working’’

I hope that makes more sense.–
The original message included these comments:

the CCU are stuck in the ‘full heat’ position. ALL of the
air entering the CCU is at ambient temperature (refrigerated
if the A/C is working) by passing through the A/C
evaporator. If the blend flaps are in the ‘full cool’


Bryan N, '91 Sovereign 4.0 L, RHD (exiled in US)
Cambridgeshire, United Kingdom
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I realize this post is old as dirt, and there’s probably another post elsewhere that actually continues this discussion, but I’m gonna give this a shot anyway …

What do you if your CCU is stuck on full heat mode?

I believe that’s what I’m dealing with on mine.

If you think the heater function is overpowering the air conditioning function and your car has no vacuum controlled heater valve (my 1990 does has none) you can clamp off the heater hose as a test. I do this in the summer with my car to boost the AC efficiency.

1 Like

I haven’t got round to it by my car is doing just the opposite, full cold all the time, no matter what the temperature is set at. I presume a flap is stuck, how do I un-stick it lads? I can hear the servo motors impulsing or at least making the sound but the car is still blasting cold A/C …ok at the moment except early morning I could use warmer tootsies.

You need to remove the glove box and the plate under the glove box. You unscrew the servomotors and take them out. You turn the flaps with a flat screwdriver and check if they move easily. Connect the multimeter topotentiometer’s wire and check the operating range and resistance, whether they are buzzing. The servomotors unscrew, wash, clean the brushes in the motor and put in new grease. Install and enjoy proper operation.
I had the same, except that the top air supply wasn’t warm.

Thanks, problem is no glove box - airbag assembly instead (94MY)

Larry, next time you are feeling adventurous or suicidal you can take on that airbag removal! Lots of info in the archives including my post from days of yore:

Apologies for the poor quality photos, a link to which is provided in the above-referenced post. Looks like something taken with the digital equivalent of a pinhole camera. If you have a clue what I am referring to you, like me, are older than dirt!

I dismantled one on my parts car Mike but so far haven’t had the gumption to take the one out of my daily …soon tho, soon …thanks for the refresher - appreciate it as I forget how I did it -and- I am old as dirt - you can tell I’m from another era because I don’t have a leg or arm completely covered in meaningless tattoos.

Now, now, Larry. Tattoos always have a purpose, but as Jimmy Buffet sang in one of his songs, “…It’s a permanent reminder of a temporary feeling.”

I belive your car has a vacume controlled heater valve, mine does and its an 89. From 90 onwards they were not installed, its located at the fire wall on the hot pipe that enters the wall, Johns suggestion to clamp it is correct. but you should replace the valve, your original will not be operating.Good luck

Well almost. They were reintroduced I think in some 92’s but definitely fitted to the 93 and by 94 the car had a slightly different one - which, BTW, is impossible to source if you need a replacement. All other year valves (where fitted) are readily available.