[xj-s] Climate Control

XJ-S
21

First, make sure that BOTH blowers (one above each footwell) are
operating. This can be confirmed by alternately removing each blower
fuse to see that the other blower operates, fuse #3 (20A) in the right
fuse panel for the right blower, and fuse #3 (20A) in the left panel
for the left blower.

Here are some tests for proper climate control operation that Bryan
Neish, the resident XJ40 expert, posted on that list, which are
applicable to all models with the Delanair III climate control (such as
your 92 XJS). Please do these tests and post back, indicating any
results that differ from the proper results. These tests do NOT
include test or mention of the Heater Control Valve (HCV), which may
also cause your problem:

HVAC system. 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’.

Also, see this site for some diagrams of the blend flap operation at
the bottom of the linked page:
http://www.skjagtech.co.uk/support-pages/generic-support/delanair-mk-3-support.html

George Balthrop, Clifton, VA USA
89 and 85 XJ-S Coupes; 89 XJ40 VDP-----Original Message-----
From: Prodriller dutch.breuklander@eqdepot.com

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

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22

No vacuum is correct for heating mode.

Call up cooling on the temp control. You should have vacuum at the heater
valve vac hose

Cheers
Doug Dwyer
Longview Washington USA
1995 XJR

The coolant valve moves freely. I felt no suction in the supply
line. Where is the source of the vacuum located under the dashboard.

// please trim quoted text to context onlyFrom: “Prodriller” dutch.breuklander@eqdepot.com

23

In reply to a message from Prodriller sent Sun 27 Dec 2009:

I have checked the vacuum system and it appears to be working. This
morning I put the settings on full heat and demist. I could hear
flaps continually cycling in the dashboard. I shut the engine off
and turned back on and the demist blew hot air. The side vents had
a slight flow of hot air but the foot vents blew cold air when the
demist was selected and when the fan was set on high. It never
blows warm or hot air out of the foot vents. Any ideas?–
Prodriller
Evansville, IN, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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