I have recently experiencing the ‘‘high fan only’’ symptom
with my vehicle’s blowers. Since there is enough info in
the archives and the on-line book, I decided to do a
complete overhaul of the blower assembly. This means
changing out the relay for the low speed as well as the
Darlington. Here is what I used, for the Darlington, it was
model # 2N6284 (the exact one in the car) and for the relay,
since I was not able to get a 30 amp one, I got a 50 amp
one, model # R-50ASD (it was the closest thing I could find
with a diode). The on-line book indicated that a 50 amp can
be used.
I carefully labeled all the connections and reattached them
with no problems. I only completed the passenger side,
with the drivers side as the next project. Anyway, when I
started the car and tested the system, turned the knob on to
low…the entire system would not work or light up. I
turned the knob to off and tried it again. After 3 tries,
it started to work and seem to have the low fan setting back
again. As I selected the Mid and High modes, the fans
seemed to be working fine. I cycled the systems several
times…low…med…high…etc. After about a minute, I
started to get smoke from behind the dash, in the vicinity
of the dash AC control unit (I still had the floor panel off
with all the exposed connections). I immediately shut off
the engine and pulled the battery cable.
Needless to say, I am puzzled as to what the problem is. Is
it because I only did the passenger side and not the drivers
side as well?
Need comments and suggestions as on how to proceed. My car
has all the doors presently open in order to get the burnt
smell out.–
1988 XJ40 VDP, NY, USA
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Sat 22 May 2010:
From a pinnacle of ignorance about things electronic, I
offer these thoughts.
The 50 amp relay that you fitted which has a diode across
the coil. Can you determine which way around that diode is
fitted? From the faintest of memories, I recall that someone
found that on some relays the diodes are fitted ‘backwards’
i.e the cathode end of the diode (the side with the
stripe) which should be attached to pin 86 of the relay on
some relays is installed the other way round and the anode
(the side without the stripe) is attached to pin 86.
What effect that would have, my lack of electronics know-how
will not allow me to guess, but I assume it cannot be good.
Perhaps you should try disconnecting the driver side blower
to ensure you not getting some feedback from that past a
wrongly installed diode on the newly rebuilt passenger side.–
The original message included these comments:
again. As I selected the Mid and High modes, the fans
seemed to be working fine. I cycled the systems several
times…low…med…high…etc. After about a minute, I
of the dash AC control unit (I still had the floor panel off
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Bryan N sent Sun 23 May 2010:
Hi Bryan,
Unfortunately, the relay is sealed and can not be opened. I
am undergoing the task of taking everything out again on the
passenger side and inspecting the blower. I will report my
results some time later today.
Good idea on checking the system without the blower in
question on and see if the system still works. It scared
the hell out of me when I saw the smoke. Don’t want to have
my car catch on fire in my garage!–
1988 XJ40 VDP, NY, USA
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Sun 23 May 2010:
Another thought.
Doesn’t that new 50 amp relay have a ‘pictogram’ on the side
of the can showing which way the diode is fitted?
Aren’t both the isolation relay and the high speed relay the
same type / form (both are Jag # JLM771)?
If so, after you have disconnected the re-worked passenger
side blower and tested OK the system with only the driver
side connected (presumably it will only work on ‘high’ so
one of the relays must be good), why not remove that relay
and fit it in to the passenger side in place of the new 50
Amp you previously installed. That may prove something (or
not!).–
The original message included these comments:
Unfortunately, the relay is sealed and can not be opened. I
am undergoing the task of taking everything out again on the
passenger side and inspecting the blower. I will report my
results some time later today.
Good idea on checking the system without the blower in
question on and see if the system still works. It scared
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Bryan N sent Sun 23 May 2010:
Bryan,
Yes they are the same relays. If you are familiar with the
sketch scribed on each relay, it shows you what each pin is
connected to but it doesn’t show the direction of the diode.
The same is true for the new relay.
I just finished disconnecting the passenger blower to see if
it still smokes. It does, from the same place and I didn’t
even turn on the blower. It started to smoke immediately.
Needless to say I disconnected the battery straight away.
Now I am truly puzzled. Something is shorting out in the
middle console area and I’m scratching my head as to what it
is. All the connections are correct. There is no way to
screw up reconnecting them because the connectors will only
fit into each other a certain way. The vicinity I see the
smoking is as follows…I’ll try to be as descriptive as
possible:
If you remove the kick panel and glove box, you will see an
array of thin rectangular connector pins on the bottom left.
They are almost level with the radio/AC controls on the
console. They are not connected to anything (which I find
curious, however there are other smaller connectors within
the rear bottom and right side that go nowhere either.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Sun 23 May 2010:
Update…
I yanked the passenger blower and there was no evidence that
the area burned…not even a faint smell. Therefore, it has
to be with the connectors, especially since it smoked
straight away earlier without the blower connected. I’m
resistant to removing the middle console unless it’s
absolutely necessary.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Sun 23 May 2010:
Are you referring to the three 15-way white connectors in
the aft edge of the A/C ECU which is affixed to the right
side panel of the climate control unit over the tranny tunnel?
IIRC, those connectors are ‘two-way’ affairs - one side
plugs in to the A/C ECU and the other side is open to
atmosphere. Gawd knows why - must be something to do with
the Jag Diagnostics plug-in system.
I didn’t think it was possible (due to loom restrictions) to
plug those in incorrectly, but just in case …
The pins are numbered 1 to 15 from the top of each
individual connector. Just make sure that pin #1 on each
connector - i.e the one at the top of the connector in each
case - have wires attached as follows :-
AC2 - UPPER #1 = Light green/orange wire
AC3 - CENTRE #1 = Orange wire
AC4 - LOWER #1 = Blue wire–
The original message included these comments:
If you remove the kick panel and glove box, you will see an
array of thin rectangular connector pins on the bottom left.
They are almost level with the radio/AC controls on the
console. They are not connected to anything (which I find
curious, however there are other smaller connectors within
the rear bottom and right side that go nowhere either.
Still in the dark on this issue.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Bryan N sent Sun 23 May 2010:
Bryan,
You’ve identified the correct items (3 rows of 15 pin
connectors) however, they were never attached to anything.
Do you recommend that I trace these wires out even though
they are always exposed?
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Sun 23 May 2010:
Are you saying that those three 15-way connectors are not
plugged in to the A/C ECU???
I’ll send you a photograph off-list showing those connectors
plugged in to the A/C ECU on my car. You will note the light
green colour on the edge of the white connectors - that is
tape over the exposed contacts on the back of the connector
IIRC.
Those white connectors (numbered AC2, AC3 & AC4 from top to
bottom) have direct connections to the A/C panel on the dash
(via 24-way yellow connector AC1, ) as follows.
AC1- pin 1 = Black wire to AC2- pin 2
AC1- 2 = White/red wire to AC2- 9
AC1- 3 = Pink/black wire to AC2- 13
AC1- 4 = Slate/black wire to AC2- 14
AC1- 5 = Red/black wire to AC2- 15
AC1- 6 = White/black wire to AC3- 12
AC1- 7 = Slate/blue wire to AC2- 12 (and Recirc solenoid)
AC1- 8 = Orange/black wire to AC4- 14 (and blower motors)
AC1- 9 = Yellow/black wire to AC3- 4
AC1- 10 = Yellow/light green wire to AC2- 8
AC1- 11 = Blue wire to AC3- 9
AC1- 13 = Red/black wire to AC3- 10
AC1- 14 = Red /orange wire to AC3- 8
AC1- 15 = Brown/green wire to AC4- 5
AC1- 16 = Orange wire to AC3- 13
AC1- 17 = Not used
AC1- 18 = Black wire to ground
AC1- 19 = Slate wire to CPU
AC1- 20 = Red/pink wire to instrument panel lighting
AC1- 21 = Blue/green wire to instrument lighting
Presumably from that information you can disconnect both
ends and determine if something is shorting to ground that
shouldn’t?–
The original message included these comments:
You’ve identified the correct items (3 rows of 15 pin
connectors) however, they were never attached to anything.
Do you recommend that I trace these wires out even though
they are always exposed?
If so, am I tracing them back to the climate controller on
the console?
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Bryan N sent Sun 23 May 2010:
Bryan,
Thanks for the pin out info. I will check and see what I
can find. I have a Jaguar manual (it’s not on CD but PDF’s)
that have all the electrical info. I’m not an electrician
so this should be very interesting proceeding. Thanks for
the info. It is truly appreciated.
As for the 15 pin connectors, they are attached to some
solid black plastic body (don’t know the name of the
component however, there is an exposed pin side like you
showed me in the pic off-line. Once again, those pins have
always been exposed and were never attached to anything. I
thought they may be some diagnostic plug in receptacle. Oh
well : (
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Sun 23 May 2010:
UPDATE
After reviewing the electrical diagrams, I found that the
wire color information was completely off. The diagrams I
have are for the 1988 MY XJ6 & VDP. This included all the
main harness diagrams, pin outs etc. Like I said, it was
not useful. I therefore decided to try some reverse
engineering. Firstly, I removed the climate control module.
I then Jerry-rigged all of the connections (meaning that I
connected them without putting all the hardware back in
place). I did it connection by connection, starting the car
after each one was reattached. I kept the main climate
control unit out during the entire ordeal. No smoking wires
so far. The only items I didn’t connect are the ones in the
glove compartment, which is for the light and the cabin
temperature sensor(?).
After everything was working, I connected the main climate
control unit. No response from the unit…dead Therefore,
I believe that I’ve isolated the problem has to do with the
climate control unit itself. I opened it up and did not see
any evidence of charring or the smell of burnt electronics.
The question is, do these units go bad? Apparently, the
unit I removed from the car was previously replace by the
previous owner. It had a stamped inspection sticker for
2005. It’s luckily a standard unit (DBC 5844) which I can
get on-line or elsewhere.
I was hoping to check the power feed connector inside the
console for the climate controller but I can’t seem to get
the correct wire identification. Anyone have what pin it
could be. The connector has labeling for pins 1 to 24.
Also, is there a way to test the climate control module
outside the car?
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Fritterfran sent Mon 24 May 2010:
Are you saying that the wiring details I provided in my
earlier post for all of the pins on the A/C panel 24-way
yellow connector AC1 are wrong? I very much hope they are not.
Assuming that the information I provided from my set of
circuit diagrams for an '88 model XJ6 or VDP is correct, the
ignition switched power to the A/C panel (BTW, is that what
you mean by ‘‘climate control module’’?) enters via the A/C
ECU on the Slate/blue wire on pin #7 of that connector. You
should see 12 volts on that wire when the ignition is
switched on.
The normal (only?) problem I’m aware of with that A/C panel
is failure of the micro-switch at the back of the fan speed
knob - well documented in the archives.–
The original message included these comments:
After reviewing the electrical diagrams, I found that the
wire color information was completely off. The diagrams I
have are for the 1988 MY XJ6 & VDP. This included all the
main harness diagrams, pin outs etc. Like I said, it was
The question is, do these units go bad? Apparently, the
I was hoping to check the power feed connector inside the
console for the climate controller but I can’t seem to get
the correct wire identification. Anyone have what pin it
could be. The connector has labeling for pins 1 to 24.
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
In reply to a message from Bryan N sent Mon 24 May 2010:
Hi Bryan,
Thanks for the info off line about the microswitch.
Regarding your posted information, as mentioned previously,
I’m not electrician. I didn’t realize that AC1 is actually
referring to the A/C Panel tail connector. (I identified it
as the climate control module). AC2 - AC4 are the 15
exposed pin segments beneath the kick panel. I’m realizing
all of this now after comparing it to your excellent info.
So please, no offense intended.
I guess I just need to check the female harness connector
for AC1, pin#7 location or on AC2 (top one) Pin#12 by the
kick panel for power. That will confirm if my A/C Panel is
truly dead. I read that it may be tricky testing AC2 because
touching 2 pins by mistake can cause big problems.
Thanks again for all your help. It’s assuring to know
someone truly loves these cars. ; )–
1988 XJ40 VDP, NY, USA
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !