[xj40] no warm air to defroster outlets

XJ40
4

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:-

  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 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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