1994 XJ40 air con clutch fuse on the passenger side panel
keeps blowing fuse air con blowing hot air thank you.–
Fred Gray
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In reply to a message from blueduck sent Fri 22 Jul 2011:
Fred,
Try rotating the compressor shaft nut [CLOCKWISE only] with
a wrench in case the compressor has seized (as mine did!).
If it turns OK, check the wiring from the A/C clutch relay
(a Red/brown wire) to the compressor clutch to check it has
not been damaged and ensure it is not shorting to ground.
That fuse A1 in the right side fuse box also serves the
driver and passenger powered seats lumbar support adjustment
so I suppose a short in that wiring could also be
responsible for blowing the fuse. However, I guess if the
fuse only blows the instant you select A/C on the panel,
then the fault cannot be in the powered seat circuits but
must be in tyhe A/C clutch circuit.–
The original message included these comments:
1994 XJ40 air con clutch fuse on the passenger side panel
keeps blowing fuse air con blowing hot air thank you.
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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In reply to a message from Bryan N sent Fri 22 Jul 2011:
Thank you very much Bryan will do–
Fred Gray
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In reply to a message from blueduck sent Fri 22 Jul 2011:
if the Freon is low in the compressor will that cause the fuse
to blow as a safety net have checked relay and ele blowing air
con fuse soon as I connect plug to air con only thank you–
Fred Gray
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In reply to a message from blueduck sent Sat 23 Jul 2011:
Fred,
No, low freon will not blow that fuse - the ‘trinary’
pressure switch which detects freon pressure within the
system will not allow the A/C compressor clutch relay to
energise if the pressure is too low (or too high).
You can narrow the search down now that you know that it is
the action of switching on the A/C which is causing the fuse
to blow (as opposed to something relating to the seat lumbar
adjusters).
First of all, did you try turning the compressor shaft
manually with a wrench as I suggested previously???
With the ignition ‘OFF’, if you remove the compressor clutch
relay and jump pin 30 (Brown/black wire) to pin 87 (the
Red/brown wire) in the relay base and the fuse immediately
blows, the problem is downstream of the relay - either the
clutch itself or, as I suggested previously, the wiring to
it (i,e the Red/brown wire).
One other possibility is that the Red/brown wire branches
and that branch is connected by a diode directly to ground
before it reaches the clutch. The diode is in the engine
harness in the engine bay behind the right electric cooling
fan - look for that Red/brown wire. If that diode (FED1) has
failed or the wiring to it is frayed and shorting to ground,
then the fuse will blow as soon as the A/C compressor clutch
relay is energised (i.e as soon as you select A/C)–
The original message included these comments:
In reply to a message from blueduck sent Fri 22 Jul 2011:
if the Freon is low in the compressor will that cause the fuse
to blow as a safety net have checked relay and ele blowing air
con fuse soon as I connect plug to air con only thank you
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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In reply to a message from Bryan N sent Sat 23 Jul 2011:
Thanks Bryan for your help, I did turn the compressor clutch
and it turn fine,I did check the red brown wire where I think
you are talking about where the black wire and the red/brown
meet in a clear cover and it looks ok, the blower fan inside
the car works fine but if the car is running and I plug the
green plug into the compressor while I have the car running &
air con on then the fuse will blow I will do this new you want
me to do if it is the compressor clutch does that mean I have
replace whole compressor–
Fred Gray
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In reply to a message from blueduck sent Sat 23 Jul 2011:
ok I did the jump pin 30 to pin 87 test in the air con relay
base and the fuse blew immediately, I still don’t see anything Wrong with the red/brown wire do you thing I need to pull more
out of the wire honest,or it may be the air con clutch thank
you.–
Fred Gray
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In reply to a message from blueduck sent Sat 23 Jul 2011:
Fred,
Quite clearly you have a dead short to ground on the
Red/brown wire from pin 87 of the A/C compressor clutch
relay. You can confirm that if you remove the relay and
check for continuity (Ohms range on a DMM) between pin 87
and any ground part on the car.
Where that short to ground occurs is the question. The
wiring arrangement on my '91 car is different to yours so I
cannot advise you on the routing of that Red/brown wire.
As mentioned previously, it could be that the Red/brown wire
has been damaged between the relay base and the compressor
clutch. Apparently, if incorrectly routed, it is possible
for the compressor pulley or drive belt to snag the wire,
strip the insulation and cause a short to ground.
It may be that the windings of the clutch itself are damaged
and offering no resistance to ground - i.e a dead short. I
will PM you the Sanden compressor manual with all of the
details about clutch replacement (see section 10.4 para 2) -
but it may be easier to replace the compressor c/w clutch as
a unit because special tools are required to change the clutch.
Did you find that diode FED1 I mentioned?
BTW the ‘cooling fan’ I mentioned in that earlier post
(behind which the diode is located in the harness) is the
radiator cooling fan, not the aircon blower inside the car
to which you refer.–
The original message included these comments:
ok I did the jump pin 30 to pin 87 test in the air con relay
base and the fuse blew immediately, I still don’t see anything Wrong with the red/brown wire do you thing I need to pull more
out of the wire honest,or it may be the air con clutch thank
you.
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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In reply to a message from Bryan N sent Sun 24 Jul 2011:
Bryan I do not see any diode on back side of fan in engine
compartment I see red/brown wire where it connects to a black
wire in a clear cover in the wire honest right behind the fan
is that what your talking about, I am still trying to find
this diode because this is last test before I buy new
compressor, is there anything else I need to replace with the
air con unit if have to replace the compressor thank you Bryan–
Fred Gray
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In reply to a message from blueduck sent Mon 25 Jul 2011:
Fred,
That ‘‘clear cover in the wire’’ to which you refer must be
the diode. The Red/brown wire goes to the diode and a Black
wire goes from the diode to ground on the firewall behind
the cylinder head.
This is a bit drastic - but not as drastic as buying a new
compressor - if you cut the Black wire downstream of the
diode and then jump the compressor clutch relay pins 30 & 87
and the fuse doesn’t blow, then you have proved that the
diode is the problem. If it still blows that fuse then you
can safely join / re-solder / shrink sleeve that Black wire
because you know that the diode is good and the problem is
in the compressor clutch (or the wiring to it shorting to
ground).
If you do need to replace the compressor, it would be wise
to replace the drive belt and of course you will need to
ensure that the compressor has the correct oil (amount and
type) and do the usual things to re-gas the system. You will
need access below the car to remove the compressor - and
don’t forget to charge it with oil before fitting the new
one - you can’t remove the fill/level plug when it is in place.–
The original message included these comments:
Bryan I do not see any diode on back side of fan in engine
compartment I see red/brown wire where it connects to a black
wire in a clear cover in the wire honest right behind the fan
is that what your talking about, I am still trying to find
this diode because this is last test before I buy new
compressor, is there anything else I need to replace with the
air con unit if have to replace the compressor thank you Bryan
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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In reply to a message from blueduck sent Mon 25 Jul 2011:
Blueduck…
Any time you open the system most a/c professionals strongly advise
that you replace your accumulator/drier. I personally always do.
After spending $200-300 on a rebuilt compressor it make no sense to
retain your old saturated $35 accumulator/drier.
Additionally, new ‘‘O’’ rings for the compressor lines are a must.
hopefully they’ll come with the compressor, so double check that.
Finally if you’re doing the work yourself you’ll require manifold
gauges, a vacuum pump, and of course about three pounds of freon.
(that’s pounds not 12oz cans!)–
Groove
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