1988 v12 - air con inside temp

Hi Guys,
Had quite a lot of work done on my air conditioning, new compressor, expansion valve and drier. Complete flush, new gas/oil etc. It works quite well however I just think it could be a bit colder after all the effort…Does anyone know what temperature I should be able to get the cabin down to at different ambient temperatures ? Also should I have the thermometer probe at the dash vent or in a neutral place when testing. Will appreciate any comments…

Hebe, your cabin low temp. will largely depend on how much effort you have put into insulating the floor of the cabin, and the underside of your car- never mind the ambient temp outside.
I spent a great deal of time trying to keep heat out of my "88, insulating everything I could.
To keep track of how well the A/C is performing, I bought a few fishtank thermometers, which are amazingly accurate, and switchable. The probe for the A/C is placed in the center vent, and usually shows temps in the low 40’s.( The photo is not showing A/C performance, just a test I was running.)
After replacing many A/C components, the biggest improvement for me was a new condenser.
I too have an '88 with the Delanair 3 system.

(After overnight shutdown I was comparing underhood temp to the temp inside my ignition amp, which I had placed on the firewall. Testing for accuracy.)
If you can get the Ranco thermostat to shut down your compressor sometimes, then you are winning.

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I had an '88 XJS for a few years. I was never fully satisfied with the climate control’s ability to cool the cabin…or heat the cabin, for that matter. In contrast, the Series III XJ6 I owned at the time would freeze your bones, or cook your toes, if asked to.

This was a long time ago and memory fades. However, I recall being unable to find an actual, correctable fault. I also recall that the volume of output air was less than I expected. I put it down to the system just not being all that great. Perhaps I gave up too soon, I dunno.

One thing I wondered about was airflow across the condenser and the difference between the XJS and sedan grille openings.

Dave mentioned replacing the condenser, and many have reported good result in going to a parallel flow condenser. Might be worth investigating.

Also worth considering the the operation of the heater valve and the internal flaps (drums, actually) in the HVAC case. In max cooling mode the valve should be closed and no airflow sent across the heater core. A quick test here would be to apply vacuum to the heater valve, thus closing it. If the output air is now colder then you have some investigating ahead of you on the control side of the system.



Two other things that help, are to replace the center dash outlet with one from a late facelift car to be able to direct air better. Also, disconnect and block off the vent pipes that go to the rear seat area in the console. A greater volume of air then comes out of the center and side vents providing better driver and psssenger cooling.

Also, ensure that the heater coolant valve in the engine compartment is fully closing when the system is at full cool. If it lets even a little coolant thru, the A/C has to work that much harder.

The parallel flow condensor mod definitely helps, as does removing the top plate over the radiator and ensuring the space between the A/C condensor and the radiator isn’t filled with trash, blocking air flow.

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Hi Guys,
Thank you for all your recommendations of which I comment. I have replaced the center vent with a later model one some years ago, not only does it work better it looks a lot better, all these small things help.
Regarding air going through the center console, at the back of my center console is an ash tray and not an air vent, where does the air go if there is no vent ?
I had the car back at the air con shop and found something very interesting…with the AC gauges hooked up and a thermo meter at the center vent we found that when the visco on the big fan kicked in the pressures dropped and subsequently the air temperature at the vent dropped to 8 deg C, when the visco fan kicked off the pressures rose as did the temperature to the vent to about 14 deg C.
What I deduce from this is if you have better air flow going through the condenser (when car is stationary) the AC performs much better so my next challenge will be to install a pusher fan !!!

Sounds like you have the right idea. Some owners have replaced the small OE electric fan with a more powerful unit, with good results. Probably some info in the archives.
From memory- the A/C vents close to the rear seats are simply slots molded into the console on each side of the ashtray. Not very obvious. I’ll take another look at my Cabriolet when daylight comes.

The rear vents on pre-facelifts exit at the rear sides of the console, in the gap between the console and carpet. Take out the console compartment tray (several screws) and you will see the ducting. I completely removed the ducting, and capped the outlets at the front where the ducting slides on.

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Well, memory is the first thing to fail, it seems. My Cherokee has slots in the center console, not the Jag.
Jon’s description is correct, and I capped off my rear A/C vents as he did, many years ago.
This photo may help- gap is aft of the fastener.

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Did this just recently too, no adverse effect with the heat, plenty of flow available from all the other vents with two good working blowers. Those rear vents mostly managed to blow cold AC air up between the seat and center console and freeze my right armpit in the summer. Silly design.

Wouldn’t have thought I’d ever say this but the AC performance even in low triple digits this last summer was fine in my 90. Cleaning the evaporator while I had the heater core and blowers out helped, it was filthy in there and restricting airflow.
That whole unit really needs to come out to do it well but I wasn’t quite that dedicated at the time. I used the spray foam AC coil cleaner like you use for your home outside unit and various toothbrushes and picks and rags, it was a bit tedious. Not a Jag specific malady either, any old car collects crud there over time.
I also have two pretty burly electric fans doing cooling duty, these cars seem to be hard for fans to move enough air through the nose when stationary or at low speed, no issues when moving though.


Hi Guys,
I think my idea for fitting an AC pusher fan has just gone out of the window…I noticed a structural piece of round bar which runs diagonally across the front of the car which I assume is for rigidity. The problem is that between this pipe and the condenser is only 25mm clearance which is not enough space for a pusher fan, the one I was looking at is between 40mm at its narrowest point and 60mm at its thickest point. Would be extremely grateful for any suggestions…

This is just a guess, but I wonder if a lot of your driving is in-town, and slower. Once out on the open road, you don’t need a fan at all.
Hayden makes heavy duty clutches for the mechanical fan, as well as standard duty units. I run a heavy duty fan clutch in my car for more airflow, and I have two heater valves in series, both controlled by vacuum, which means, without getting into too much detail. that I can absolutely, positively, shut off any hot water flowing through the heater core.
Have you ever replaced the fan clutch? Like most of us, they can get tired.

Hi Dave, I replaced the fan clutch with the standard jag part about 10 years ago when the engine was rebuilt which has done about 10,000km. Another aspect is that I will take the xjs with me when I re locate from South Africa to Scotland and with the ambient temperatures being lower perhaps I will not need such a strong AC…I guess when I saw the AC pressures drop as well as the vent temperature when the visco kicked in my first thought was to get the was more air flow across the condenser in the form of a pusher fan…

When you make the move, make sure that your wiper motor and blades are in tip-top shape.

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Will do …thanks for all the tips :grinning: