[xj] climate control works without being turned on!

I just got this car and don’t know much about the climate control
history, other than being told the HI fan speed didn’t work. Turns
out that in addition to that, the unit may not turn on at all, or may
turn on and blow hot air, rather the a/c as requested. Sometimes the
a/c does work–in the ‘auto’ mode.

In looking at the main blower relay, I found the two GS wires, or in
my case 1 GS and 1 LGS wire, were not attached to the relay. The
female connector on the wires looked like it had been roasted, and
though not fused together, the two green wires were stuck together
like they’d been thinking about becoming one. I cleaned everything
up, put on a new female connector and attached it to the relay
terminal. This caused the fans to come on, on HI, I think–without
the ignition on, and with the Mode switch in the off position! I
removed the BW wires from the relay and tried again. Same result.
Does this maybe mean the HI speed relay contacts are fused together in
the on position?

The servos haven’t worked for days–though they did today–and I’m
suspicious I need a new amp based on the erratic nature of the beast,
and am in the process of getting one. Should I get a main blower
relay at this point also, or do I need more testing/

Thanks.

Thon
87 XJ6===================================================
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In reply to a message from tb sent Mon 7 May 2012:

There shouldn’t be a Green/Slate wire on the relay, unless a
previous owner got creative.

There should be two identical light green/slate wires connected to
to terminal 2H on the relay.

Do you have the wiring schematic?–
The original message included these comments:

In looking at the main blower relay, I found the two GS wires, or in
my case 1 GS and 1 LGS wire, were not attached to the relay. The


al mclean '05 X 2.0 D Estate- '93 XJS 4.0 - 05 X350 2.7TDVi
Telford, United Kingdom
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tb wrote:

I just got this car and don’t know much about the climate control
history, other than being told the HI fan speed didn’t work. Turns
out that in addition to that, the unit may not turn on at all, or may
turn on and blow hot air, rather the a/c as requested. Sometimes the
a/c does work–in the ‘auto’ mode.

‘Sometimes’ is a key word, Thon…

The ‘come-and-go’, sometimes arbitrarily change between heating and
cooling, is typical for a faulty AC amplifier. Based on sensors; the
amplifier turns a servo to the appropriate position, and cams on the
servo operates the various functions via pushrods, microswitches and
vacuum valves. The AC amp/servo operations are separate from manual fan
speeds. To test amp;

*Turn ign ‘on’ and set function switch to ‘auto’. Turn the temp control
alternately between ‘65’ and ‘85’. Each and every(!) time the temp
control is reset between these extremes you should hear the servo
‘buzzing’ indicating a functioning amp/servo. Failure or intermittent
reaction is usually an amp fault - which must be then changed before
further work on the system…

The manual fan speeds are operated by microswitches on the function
switch (‘lo’/‘hi’). The microswitches then apply energizing power to the
relevant relay (a common ‘energizing ground’, black/blue fro three of
the relays is grounded by the function switch in all positions but
‘off’), and the respective relays then operates the fans from the 50A
fan fuse. In ‘auto’, microswitches on the servo operates the relays for
two ‘other’ speeds, we can call them ‘auto hi/low’, bypassing the manual
controls. The 4 relays required are placed together in a relay bank, and
only one relay is active at any one time…

The different speeds are then obtained by using a resistor unit; power
from a relay is passed through the resistor unit - connected
respectively to give the resistance required for the fan speed/relay
engaged…

The multiple connections at the relay bank is very critical - and as Al
implies; you need a wiring diagram to sort this fully. Usually one
simply ‘cheat’ by using the original connections, but in your case this
is ‘unsafe’. Again as Al says; a PO might have done a ‘funny’ - and
there is no way of telling ‘what’ and ‘why’…:slight_smile:

The best way out of the wilderness is to access the resistor unit - you
will find the green/slate to the manual 'hi’speed relay co-connected
to the green/slate going to the fan motors (NB, below). Point here is
that the green/slate to the motors carry all power to them after
passing through the resistor unit - the ‘hi’ relay simply bypasses the
resistors, to give full motor power…

The other colours on the resistor unit; yellow, blue and red -
goes to the respective relays. But sorting the relay bank connections
from scratch is a daunting prospect, and ‘impossible’ without the wiring
diagram - and even then; wiring diagrams do not necessarily show the
actual physical connections.

Principally; the ‘manual hi’ speed relay should have at least two
external wire connections; green/slate , power out to the motors, and
black/white, relay power from function switch. Nominally;
black/blue, relay ground is internal, as is brown/white, fan power
from the 50A fuse.

NB, the green/slate may be co-connected at the relay rather than at
the resistor unit, check(!) - this may explain two ‘greenish’ wires at
the ‘hi’ relay. As Al says; there are no ‘LGS’ wire shown in the
diagrams…:slight_smile:

What ‘may’ have happened is that a PO disconnected the ‘manual hi’ speed
relay because it failed ‘closed’ giving permanent high speed (which
doesn’t explain their ‘burnt’ appearance). With just a failed ‘hi’
relay; all other speeds should operate normally if the green/slates
are disconnected, but(!) kept connected together.

There are no ‘main’ relay - the relay bank consists of 4 independant
relays, which may fail singly.

And I don’t expect you to sort this from these descriptions alone…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)> In looking at the main blower relay, I found the two GS wires, or in

my case 1 GS and 1 LGS wire, were not attached to the relay. The
female connector on the wires looked like it had been roasted, and
though not fused together, the two green wires were stuck together
like they’d been thinking about becoming one. I cleaned everything
up, put on a new female connector and attached it to the relay
terminal. This caused the fans to come on, on HI, I think–without
the ignition on, and with the Mode switch in the off position! I
removed the BW wires from the relay and tried again. Same result.
Does this maybe mean the HI speed relay contacts are fused together
in the on position?

The servos haven’t worked for days–though they did today–and I’m
suspicious I need a new amp based on the erratic nature of the beast,
and am in the process of getting one. Should I get a main blower
relay at this point also, or do I need more testing

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In reply to a message from Frank Andersen sent Tue 8 May 2012:

Hey Frank…

Just reading through this, I’m trying to sort it out in my mind…
Where are the 4 relays associated with the fans?
Only thing I can think of is the one large black relay by the LH
footwell access…
Here: http://www.jagbits.com/product/C46179-OE.html
(Not my ad, yatta yatta)…

Or are you specifically taking about the four terminals(?) inside
this one relay?

Thanks!
David–
The original message included these comments:

There are no ‘main’ relay - the relay bank consists of 4 independant
relays, which may fail singly.
Frank


84 XJ6 (Driver) 89 XJS Convertable… Parts cars piling up.
Rockwell, NC, United States
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In reply to a message from DavidBoger sent Tue 8 May 2012:

David,

I presume he is. I called it the ‘main a/c blower relay’
because that’s the way it was labeled on one of the parts
schematics.

Frank and Al,

You guys get your stories straight :slight_smile: --you’re the a/c
gurus as near as I can tell! Are there or aren’t there LGS
wires on the blower relay? :wink: I didn’t see any labeled as
such on several different schematics I looked at, but I can
assure you I have 1 GS and 1 LGS that TOGETHER attach to the
high speed fan relay, and also TOGETHER attach to a blower
resistor terminal. It all looks factory.–
tab a
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DavidBoger wrote:

In reply to a message from Frank Andersen sent Tue 8 May 2012:

Hey Frank…

Just reading through this, I’m trying to sort it out in my mind…
Where are the 4 relays associated with the fans?
Only thing I can think of is the one large black relay by the LH
footwell access…
Here: http://www.jagbits.com/product/C46179-OE.html
(Not my ad, yatta yatta)…

Or are you specifically taking about the four terminals(?) inside
this one relay?

It’s actually four separate ‘relay functions’ built into one box, David

  • and is indeed the one shown in the Jagbits list…

But to be absolutely fair; while the wiring diagrams show them as 4
separate relays; it is possible that they have been ‘compactified’ one
way or another - while retaining the ‘four relay’ functions. This is
part of car ‘electrickery’, smart solutions not shown on wiring diagrams

  • we all know the difference between tracings of diagrams and the
    physical aspects of layouts…

As the saying goes: “One is chart to understand - ship to handle is
another matter”…:slight_smile:

It is, however, perfectly possible to substitute one ‘relay’ with an
external one - leaving the omitting those connections on the original
bank. Or indeed get a new relay bank - if a stuck relay is his only
problem…

Frank
xj6 85 Sov Europe (UK/NZ)>The original message included these comments:

There are no ‘main’ relay - the relay bank consists of 4 independant
relays, which may fail singly.

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Hi David,
That large black ‘relay’ is really an enclosure with four relays
inside it, that’s why it has so many connections. If you take a look at
Kirby Palm’s XJS book here on the Jag Lovers’ site there’s a pretty good
section on the climate control, which is the same as the XJ, showing the
four relays and their functions.
John Hudson
85 XJ6 SIIIOn 9/05/2012 7:01 AM, DavidBoger wrote:

In reply to a message from Frank Andersen sent Tue 8 May 2012:

Hey Frank…

Just reading through this, I’m trying to sort it out in my mind…
Where are the 4 relays associated with the fans?

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tab a wrote:

In reply to a message from DavidBoger sent Tue 8 May 2012:

…Are there or aren’t there LGS
wires on the blower relay? :wink: I didn’t see any labeled as
such on several different schematics I looked at, but I can
assure you I have 1 GS and 1 LGS that TOGETHER attach to the
high speed fan relay, and also TOGETHER attach to a blower
resistor terminal. It all looks factory.

It may be a sort of belt and braces, Tab - but I could not find any sign
of light green/slate anywhere in the AC diagrams either…

The function of the wires is very simple; a green/slate carries fan
power from the resistor unit to the motors. All power goes through this
wire, but except for ‘manual hi’ speed relay; power from the other
relays are first passed, as appropriate, through the various resistors
in the resistor unit for fan speed regulation…

The ‘manual hi’ relay terminal is connected directly to the
green/slate motor wire at the resistor unit as said before. Which is
really all there should be, making two green/slate at the resistor
unit - or indeed two green/slate at the relay terminal. However, to
complicate matters somewhat; the diagram of the resistor unit is not
quite correct…so there…:slight_smile:

The anchor point remains the green/slate to the motors, and jumpwiring
this to a power source should run the fans - for verification. The
brown/white should do…

Next; the relay should be checked out; the green/slate terminal should
show no power with the system in ‘off’ - ign ‘on’. Relay power at this
stage implies a frozen relay - switching the function control to ‘hi’
should give power, but not in ‘lo’ and ‘auto’…

All with some uncertainty as the only clue at this stage are the wire
colours, and a PO may have mixed up the connections. However, keeping
the ‘manual hi’ terminal disconnected - you should now have normal ‘lo’
and ‘auto’ fan actions, but ‘def’ may rely on the ‘manual hi’ relay and
be missing…

These are just clarifications; the mystery of the light green/slate
remains to be resolved later - just record the connections as a memory
back-up.

Also unresolved is the ‘burnt’ look of the wires; these wires are
designed to carry continous high current to the fans - and the 50A fuse
is supposed to blow before the wires burn. However; the ‘burn’ may just
be caused bay a bad terminal connection…:slight_smile:

so…?

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
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tab a wrote:

…Are there or aren’t there LGS wires on the blower relay? :wink: I
didn’t see any labeled as such on several different schematics I looked
at, but I canassure you I have 1 GS and 1 LGS that TOGETHER attach to
the high speed fan relay, and also TOGETHER attach to a blower resistor
terminal. It all looks factory.

After previous interchanges; I have done some ‘thinking’, Tab…:slight_smile:

The wiring diagram shows the original lay-out with 4 fan speeds;
‘autoLo’, ‘manLo’, ‘autohi’ and ‘manHi’. I ‘think’ that Jaguar may have
found the ‘autoHi’ fan speed unsatisfactory - and modified the wiring to
increase it. Simply adding a wire, like light green/slate(!) between
the ‘autoHi’ connection at resistor unit and the 'manHi" speed relay.

This effectively bypasses the ‘autoHi’ resistor restriction - and gives
max fan speed in ‘autoHi’. This gives green/slate and light
green/slate
wires at the ‘manHi’ relay (as observed) - and two
green/slate wires at the ‘fan motor’ connection of the resitor unit.
There should then be two wires of one of the other resistor unit
connectors - likely giving one blue and one light green/slate;
assuming blue is ‘autoHi’ relay…:slight_smile:

If so; the PO has not ‘fumbled’ the connections - possibly faced with a
frozen ‘manHi’ relay he simply disconnected it, though the ‘burnt’ wires
is still unexplained. As long as the the two wires are still connected;
you should then have the fans working as intended, but of course missing
the ‘manHi’ switch-on. Which is the same as the ‘autoHi’ speed in this
setup - but the latter only working with the system set to ‘auto’…

Which gives only three fan speeds ex-factory, but the modification would
only involve an extra bit of wire; no other changes to parts or lay-out
twould be required - which is a typical Jaguar way of evolving. A point
here was likely that it was done on later models Delanair II - as a
stopgap before the planned installation of the Delanair III; which uses
electronics to regulate fan speeds among other changes…

Whatever the reasoning; this is a simple modification for anyone wanting
higher fan speeds in ‘auto’ - for possible improvement in system
performance. Or reversing the modification if one wants lower fan speed
in ‘auto’, of course…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
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