Bob I just checked the pressure graphs in my manual and it shows the high side pressure should be between 200-250 PSI at 95F (bit less for 92F). For an evaporator temp of 50F the low side pressure should be about 45 PSI.

The system refrigerant capacity is 950g +/- 50g

Not sure if your system is the same but hope this helps.

Cheers,

Allan

 

The "point" is that at 92 degrees out R134 at idle will produce a duct temp of about 50 degrees...which is what you have which is "normal". At "speed" the condensor can get rid of heat better and you'll get a duct temp of aroud 46 degrees or so which again is "normal" I think the point is you're thinking you can get it lower and I'm trying to tell you that you won't, recirc or no recirc there doesn't seem to be anything wrong. Try spraying some water over the condensor at idle and see if the duct temp doesn't come down a tad as if you were at speed. The OAT affects the gas/liquid because it is affected by it in the condensor outside of the cabin and its ability to get rid of built up heat....windows up, 92 out, 50 to 45 at the fascia is plenty cool enough...I just drove home in mine in NE Florida with an R134 conversion and mine was plenty cool inside and I'll bet the center duct temp was no lower the 48 at best.

 

Allan,

I believe the '93 model year for XJS's was a big change for Jag......the first 6-litre engine and new body work on the windows, the 4-speed automatic with the V12's, etc. Was this the year they went to the A/C system that I have without the recirc. button? Did the previous years of 5.3 litre V12's have a recirc. button?
When they made the change in early "94 to the system you have, they must have done this resulting from complaints and poor cooling performance from cars without the recirc. button.
I checked in my Jag Parts microfiche and they do show both of the A/C control panels, the one for my type is listed as "Clarion E950"
Do you thiink it would be worth my time to write Jaguar asking them if there is a kit or some other fix for this problem?
Regarding your warning about over-charging the system, this would show up in the manifold gauge readings being too high and my readings are normal.
Thanks again Allan, you have given me a lot of helpful information for my problem.

Take care,
Bob
'94 XJS-V12

 

Not quite, although Jag made very modest changes to the XJ-S during it's first 17 years of production, they then made some very significant changes in each of the following 4 years. Briefly the major changes were:

1992 Major facelift, new body work, lights, windows. New instrument panel, new center console controls (trip computer/radio/AC) Only engine available in the US 5.3L V12 w/3spd auto.

1993 5.3L V12 dropped, 4.0L I6 introduced with 4 spd auto or 5 spd man. There were 100 of the XJR-S imported that had a special 6.0L V12 that is a different beast to yours but still had 3 spd auto box.

1994 6.0L V12 with 4 spd auto introduced. Rear brake discs moved to outboard, new a/c system with R134A refrigerant and (after VIN 190528) new control panel.

1995 AJ16 engine replaces AJ6


As far as I know the XJS never had a recirc button/mode until the MY94 changes.


Although it would be possible, I imagine it would be extremely expensive. At a minimum I would think that you would have to replace the center console switchgear, the wiring harness and the A/CCON and gosh knows what else!!


Not sure if you saw my earlier post but it does look a bit high on the high pressure side and a bit low on the low pressure side based on the specs for my system.

"Bob I just checked the pressure graphs in my manual and it shows the high side pressure should be between 200-250 PSI at 95F (bit less for 92F). For an evaporator temp of 50F the low side pressure should be about 45 PSI.

The system refrigerant capacity is 950g +/- 50g"

Cheers,

Allan

 

Going to have to take a few days off.....I've had an equipment failure. When this is fixed, I'm going to evacuate and recharge the system with the exact amount specified and will record the manifold gauge readings.
Until then,
Take Care and thanks,

Bob

 

I agree with just about everything you said with the exception of the duct temp. not changing relative to feeding inside or outside air into the evaporator. I'm going to ask Allan to do a test on his using recirc. as opposed to outside air, both under the same conditions. Today I evacuated and recharged mine using the correct amount of freon. When I did the job this morning the OAT was about 86F. I had a squirrel cage blower from a 4-ton house unit in front of the radiator so the condensor was getting plenty of air. Engine at about 1200rpm, I got a duct temp of 48F deg. Tomorrow I will take it out on the street and see how it does. Thanks for your input.
Bob

 

Allan,
Since you are the only one with a '94 with a recirc. button in this thread, when you get a chance would you do a little test for me. Measure the duct temp. with all other conditions being the same, in both outside air and recirc. modes Blower speed medium and temp. control at max. cold.. Don't expect any temp. changes right away, I think you should give
the unit at least 5 minutes to react. If possible, do the test at a hot time in the afternoon. I'm curious to see how much difference there is.
Thanks again for your help.
Bob

 

Bob,

I'll be happy to. Will try to get to it tomorrow, should be at least mid 80's here.

BTW when you evacuated did the refrigerant pull out any PAG oil and if so did you replenish?

Cheers,

Allan

 

I never said "recirc" wouldn't change the duct temp, just that the duct temp you're getting is "normal" for r134 and your conditions. If you had recirc I would expect maybe a 2 degree drop in duct temp as your cooling already cooled air. The OAT will impact the duct temp based on its effect on the condenser so duct temps will change based on OAT recirc or no recirc. The "auto" mode IIRC will adjust between norm/recirc/heat/evap based on the cabin temp which is why the "recirc" button may not be present...IIRC it shifts things as it feels necessary too maintain the desired temp in the cabin.

 

I will be interested to see the results of Allan's test with recirc/outside air. This morning I started the car, the ambient was 87F, blower on medium speed, rpm's @ 1500, no squirrel cage in front of radiator and I got a duct temp. of 45F. That's the best I have ever seen it so I am satisfied that my system is performing normally. Wish I had a recirc. button, but there is nothing I can do about that. Thanks for your input.'\

Bob

 

No, did not pull out any PAG oil so did not replenish. Thanks,
Bob

 

Bob, my 86 has no "recirc" switch but does switch between inside and outside air as deemed by heat vs cool and by the "auto" function. Some luxury cars don't carry a "recirc" function as too long in that constant operation will "stale" the air. Sounds like yours is up to snuff and will perform just fine. My 99 Explorer Limited had a "manual" "recirc max" or "auto" I ran it in "auto" and the blend doors and blowers would do as they needed between recirc, outside, evap or heat core to keep that temp, humidity at a constant level as selected by the temp knob.....similar to the Delanair in "auto"

 

Ok Bob, I just got home and these are my findings.

When I left the house this morning it was 75F ambient and 67% rel humidity. On the highway after 30 mins of driving, I set cruise control at 75mph which on my car is 2500rpm. I set the climate control to manual, A/C on, fan speed position 2, face level slider at mid point and temp dial set at coldest (65F).

After 10 mins I measured the center duct temp and got a reading of 42.1F.

I then pressed the recirc button, waited another 10mins and got a reading of 40.4F

After lunch with ambient temp now at 86F and 56 rel humidity, I drove around town in typical stop/go fashion with speeds varying from 0-45mph. With recirc off I measured 48.6F and 46.4F with recirc on.

On the way home on the highway, still at 86F ambient and same conditions as before, I measured 45.2F without recirc and 44.1F with.

Just for giggles I increased fan speed to 3 and that improved non-recirc to 44.6F though the temp with recirc on stayed at 44.1F

At all times my auxiliary electric fan was off (it does not come on in my car unless coolant temps get above about 212F) which probably affected the ability of the system in stop/go traffic.

So it sounds as though your system is pretty much spot on, now I just need to go warm my toes up!!

Cheers,

Allan

 

Like I said...about 2 degrees cooler with recirc on...and I didn't spend a dime on gas! JK!

 

Fan speeds don't effect temperature for the most part except that they do provide some evaporative/expansion effect and therefore will drop it some but very little...little that a temp gauge will pick up but running the fan at low speed will provide better mositure removal which will make one feel more comfortable at a higher temperature once the temperature has stabilized (think how the low speed blower takes over in the auto mode once the high speed blower has stabilized/brought down the temp) also "wind chill" when blown over you will make one feel cooler by evaporating sweat at higher rate...it's why dogs hang out there tounge out a car window with their face exposed to the breeze!

 

Allan,
You sure went to a lot of trouble to do the test and I really appreciate it. I thought the temp. difference between outside and recirc. would be more like 5-8 degrees but your figures don't lie. And yes, my system seems to be working normally. Some of my problem was I did not fully understand how my system works.....I was not aware that I had a recirc. mode which is chosen automatically by the ACECU according to what is needed to accomplish the driver's request. JTsmks was a big help in providing me with a detailed description of the system function. For this I thank the both of you.
This thread is well worn so let's put it to sleep.
Now I'll see if I can open another can of worms!!
Take Care,
Bob (Spillwaybob)

 

JTsmks,
See my reply (#36) to Allan.
Off Subject, why do your wiper blades park on the right side and mine park on the left??
All of these little subtle differences between 20 years of XJS production have yet to be discovered!

Bob

 

I dunno? I never really noticed any differances. Come to think of it my 87 XJ6 Series III parked on the right too. Glad the A/C is sorted...never fear, something else will come up...it always does

 

Hey all you A/C Sperts!
My A/C has been working fine, especially now that our ambients are below 90F and I learned how to use it.
BUT, yesterday a new wierd problem has occured. The system won't turn off with the blower switch in Off. The blower and Compressor clutch cycle rapidly----about every 3 seconds, the blower and the clutch click on just for a fraction of a second, a 3 second pause and then it repeats. Ignition switch in run position, engine on or off. Moving the blower switch to the other positions work fine as it should, the problem is only in OFF.
Anybody ever hear of this problem????
I need help again>

Bob (Spillwaybob)

 

Hi Bob,

Heh heh, it's always something

Perhaps a dodgy connection on the fan speed selector switch? If ok there, check the connection on pin 9 of the CCM. After that it will be a bit of a rabbit hunt I'm afraid
Nothing really easy to get to in the A/C control system.

Cheers,

Allan