Jaguar XJ-S. Manual - part 130

 
 

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fully charged and the sight gauge is still bubbling, not clear.  This is not a good solution, since an inadequately-charged 
system won’t cool efficiently and will generate excess heat in the compressor. 

The way to lower high side pressures is to increase the airflow through the condenser coil in front of the radiator.  The 
airflow is marginal in an XJ-S at idle, since the engine turns slowly and the belt-driven fan doesn’t move much air and 
the electric fan isn’t much help.  Leaves and debris packed in the air path, notably between the condenser and radiator, 
reduce airflow.  But worse yet, the foam that originally surrounded the radiator and condenser is likely to be 
deteriorated or missing altogether; the tendency of the XJ-S radiator to get plugged up means that it is removed for 
renovation periodically, and some morons claiming to be mechanics deliberately leave the foam out during reassembly, 
claiming it is unnecessary.  As a result, the air the fans are pulling through the radiator is taking the easier path around 
the condenser, and airflow through the condenser is nil.  This can result in high side pressures that are not only high but 
rising with no sign of stopping.  Of course, when the car is moving at 60 mph the airflow through the condenser is fine, 
but this won’t help get the system properly charged. 

As you stand looking into the engine compartment, the problems of airflow through the condenser coil are not obvious. 
 You can see the fans turning, and most A/C mechanics naturally believe that if the fans are running the airflow is OK.  
They are not likely to correctly diagnose the problem as missing foam packing, even though they may comment that the 
symptoms resemble what happens when the fans aren’t working. 

Make sure your condenser, oil cooler, and radiator are properly packed with foam to prevent air bypass; see page 226.  
Make sure the fan shroud flaps are working, too, as described on page 225.  Obviously, make sure your radiator fans 
(belt-driven and electric) are in good working order, including the fan clutch which is notorious for looking like it’s 
working fine while not moving enough air.  If your car is an earlier model in which the supplemental air valve is not 
used to raise the idle speed when the compressor is engaged, consider retrofitting that particular feature; a higher idle 
with the compressor engaged will cause the belt-driven fan to move more air through the condenser.  See page 303.  If 
your car is a later model in which the small electric fan doesn’t come on with the compressor, consider retrofitting that 
particular feature.  Finally, consider an electric fan upgrade; see page 219.  All in all, any maintenance or upgrade 
intended to keep the engine cool by improving airflow through the radiator will also help keep the A/C condenser 
cooler and therefore the freon pressures lower. 

Once you have the airflow moving through the condenser like it’s supposed to, have the system checked and fully 
charged as necessary.  Make sure the system is fully charged to the point there are no bubbles in the sight glass; if the 
tech doing the charging has any hesitation about properly filling it due to excessive high side pressures, you need to do 
more work on the condenser airflow. 

To keep those high side pressures down while charging, you could put a box fan standing on the ground in front of the 
car blowing into the front grille.  You can even spray a garden hose into the front of the car, which should bring the 
freon pressures down considerably.  This might help convince you that you understand the problem, but it’s not a 
solution; you want to be able to rely on this A/C system when stalled in traffic on a sweltering summer day, so you need 
to make sure your system will maintain reasonable pressures without resorting to such measures. 

 

FREON REPLACEMENT:  Production of R-12 has been prohibited since 1995, the price for the remaining stocks and 
recycled R-12 is high and can only be expected to continue to rise, and many XJ-S owners are finding it advantageous 
to convert the system to an alternative refrigerant. 

The most popular scheme is to convert to R-134a refrigerant.  This decreases the capacity of the system somewhat, but 
since the A-6 compressor is adequate to cool a Chevy van it’s not likely to lack ooomph in this application. 

Another option is R-406a.  More expensive than R-134a, but is not only a drop-in replacement for R-12, it also 
increases the capacity of the system by a few percent.  There is more info available on the WWW at: 

 

http://www.worldserver.com/r406a/

 

Other possibilities include a host of substitute refrigerants such as Freeze-12, FRIGC FR-12, Hot-Shot or GHG-X4 
(GHG in honor of the chemist who put the formula together, George H. Goble), supposedly direct replacements for R-

 
 

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12 with little or no conversion necessary.  Any search of the WWW is likely to turn up a flurry of information on R-12 
substitutes.  Or call McMullen Oil at 1-800-669-5730 or Monroe Air Tech at 1-800-424-3836. 

Tony Bryant touts the advantages of converting to “a non-EPA-controlled refrigerant”:  “Use 30% BBQ propane and 
70% camping gas (make sure it’s iso-butane, not n-butane).  Or just buy a bottle of commercially available refrigerant 
of roughly this composition.  Some states don't allow these blends but they are available commercially and are 
apparently quite popular, especially in Australia.  They work very well, at least as well as R-12, and are practically free. 
 Also they have no problems with moisture contamination.  Flammability is obviously a potential issue, but don't let that 
hold you back.  All vented compressor oil is flammable anyway.” 

There is one overriding advantage to choosing R-134a over all of the other substitutes: it can then be serviced by any 
auto A/C repair shop in town.  Shops are required to have a separate refrigerant recovery system for each type of 
refrigerant they deal with, and they all have such recovery systems for R-12 and R-134a.  Peter Cohen says, “Since 
every damn one of these refrigerants requires distinct fittings and separate recovery equipment, most shops will only 
service R-12 and R-134a.  People have been scared into believing that no one will fix their car if they have a problem 
away from the shop that did it in the first place.” 

 

CONVERTING TO R-134a:  Converting the R-12 system in the XJ-S to R-134a is covered in some detail here.  
Conversions to other substitutes are not covered at all; you’re on your own. 

In its simplest incarnation, converting an R-12 system to R-134a requires the following four steps, outlined in any kit 
available in any auto parts store: 

ƒ  Evacuate the system, recovering and recycling the old R-12 

ƒ  Install conversion fittings to the high and low side ports 

ƒ  Recharge the system with one 11-oz. can of ester oil and the proper amount of R-134a refrigerant 

ƒ  Apply a sticker indicating the conversion 

In addition, many experts will tell you that you need to: 

ƒ  Replace the hoses 

ƒ  Flush all the old oil out of the system 

ƒ  Remove components (compressor, condensor, etc.) and manually drain the old oil out of them 

ƒ  Replace the O-rings 

ƒ  Replace the shaft seal on the compressor 

ƒ  Replace the compressor 

ƒ  Replace the expansion valve 

ƒ  Replace the dryer 

ƒ  Replace the condenser 

ƒ  Install a high pressure limit switch 

ƒ  Replace or adjust the compressor cycling switch 

I hasten to point out that many of these additional requirements were originally touted by experts when the ban on R-12 
was first proposed without any experience to back them up.  Now that R-134a conversions have been done for many 
years, experience has shown that each and every step is absolutely necessary and that each and every step is a complete 
waste of time and money -- depending on the individual situation.  Of course, many people will insist one way or the 
other on each one, largely depending on whether or not they’ve ever had a problem doing a retrofit.  In the following 
sections I endeavor to explain each concern in enough depth that you understand how the concern applies to your car.  

 
 

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Note that shops who offer to do such retrofits face considerable risk when quoting a price for the basic steps; if it turns 
out that some of the additional steps are necessary, they could be in for serious losses.  Keep that in mind when you 
negotiate with a shop to do such a retrofit, and try to indicate a willingness to accept that additional steps may be called 
for and to pay for them.  If you don’t, the shop is only too likely to quote you an up-front price including all those steps 
whether they prove necessary or not. 

I also hasten to point out that the basic steps described in the kits presume that you are converting a perfectly working 
R-12 system.  I’m gonna go waaaay out on a limb here and presume that you are not planning to convert a perfectly 
working R-12 system; the only reason you’re in here at all is because something broke.  That being the case, note that 
repairing a damaged system and recharging with a different refrigerant than it had before can result in inevitable 
uncertainties about just what caused what if the system fails to perform as expected.  Keep that in mind when 
negotiating with a shop to do the repairs, remembering that they will be inclined to quote an up-front cost to cover any 
and all contingencies -- including the possibility that you, the customer, will be dissatisfied with the performance of a 
perfectly-functioning R-134a system. 

Finally, note that -- as explained in the sections below -- there are some concerns unique to the Jaguar XJ-S when doing 
an R-134a retrofit.  Many shops may have had bad experiences doing such retrofits on XJ-S’s or have heard about other 
shops that did, and may quote you an outlandish price or refuse to work on the car altogether. 

Jaguar offers a retrofit kit; the part number is JLM 11610 for the 1993-94 XJ-S with a Sanden 709 compressor, and 
JLM 11611 for the 1979-92 cars with the Harrison compressor.  To quote from Technical Service Bulletin #8239:  
“The primary changes involve the replacement of the existing compressor lubricating oil with an oil compatible with 
both HFC R-134a refrigerant and with the residual R-12 lubricating oil.  It is not possible to completely flush R-12 type 
lubricating oil from the refrigerant system prior to changing to Ester oil and R-134a.  Additionally it is necessary to 
replace the input shaft seal of the compressor with a seal compatible with the R-134a refrigerant and oil.” 

Retrofitting an R-12 system is not the same thing as building a system from scratch to use R-134a.  For a comparison, 
Richard Jackson provides the following excerpt from the August 1993 version of the ROM: 

CLIMATE CONTROL SYSTEM INTRODUCTION 

The climate control system fitted to the 1994 Model Year XJS has many features which make it 
unique.  These differences demand changes to current system maintenance and rectification 
working practices. 

 

Feature 

  1.. Refrigerant HFC 134A (Hydro flourocarbon, non ozone depletory). 

  2.. PAG (polyalkylene glycol) synthetic compressor lubricating oil. 

  3.. Dedicated and improved compressor for HFC 134A refrigerant. 

  4.. Quick fit/release self sealing charge and discharge ports. 

  5.. Dual pressure switch to control compressor (incorporated into liquid line). 

  6.. Clamp retained 'O' ring seals at the expansion valve and evaporator. 

  7.. All aluminium evaporator matrix and pipework. 

  8.. Aluminium receiver/dryer (without sight glass) and HFC dedicated desiccant. 

  9.. Parallel flow extended height condenser. 

 10.. Single muffler situated in suction hose. 

 11.. Improved electrical system connectors. 

 12.. Improved system control panel. 

 
 

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“The key point to note from the above is that Jaguar have gone to some lengths to change the system for R-134a in 
comparison with the earlier R-12 systems.  In addition this updated system is fitted with a Sanden SD-7H15 compressor 
with capacity of 155 cm3 / 9.5 cu inches per revolution (the same capacity as the Sanden 709 fitted to the R12 4.0L 
XJS).” 

If you’d like more information on R-12 to R-134a conversions, there is a Q&A at 

 

http://www.aircondition.com

 

 

SERVICE PORT FITTINGS:  Regulations require that a different and non-interconnectable type of service port be 
used with each different type of refrigerant.  So the service ports on an R-12 system are different than the service ports 
on an R-134a system; the R-12 service ports are externally threaded, while the R-134a service ports are a quick-
disconnect design with an internal thread to hold the caps on.  When you are converting an R-12 system to R-134a, you 
must adapt the R-12 service ports or replace the hoses in entirety to provide R-134a ports. 

If you’re buying new hose assemblies as part of your conversion, simply order the correct hoses and they will come 
with R-134a service ports.  If you’re intending to reuse/rebuild the R-12 hoses, you will need to screw adapters onto the 
service ports to render them R-134a service ports instead of R-12 service ports. 

This would be simple enough if there were only one type of R-12 service ports, but no such luck.  Obviously, it would 
make sense if the high pressure service port was different than the low pressure service port so you couldn’t mix them 
up.  It may be obvious to you and me, but apparently it wasn’t obvious to somebody way back when because up until 
1976 the two ports on an R-12 system were exactly the same.  In 1976 somebody’s lawyers pointed out the financial 
implications associated with freon cans exploding in customers’ hands and the high pressure port on R-12 systems was 
changed to make it different than the low pressure port.  In the US, anyways.  Then in the 90’s GM apparently decided 
that wasn’t good enough and changed the design of the high pressure port again.  Throughout all this, the low pressure 
port remained unaltered. 

You need the correct adapters for the type R-12 fittings you have.  You have a mid-80’s XJ-S so you need the 1976-on 
versions, right?  Wrong.  Mike Aiken says, “The Jaguar A/C fittings are pre-1976 standards.  Both hi and low sides are 
the same size, 7/16-20.”   Jaguar may not be the only import that stayed with the obsolete standard; some kits to adapt 
these fittings are described as “pre-1976 and Europe” or “pre-1976 and some late model imports”. 

So, you need to check carefully that the kit you purchase contains the correct adapters -- specifically, that it has the 
correct high pressure adapter.  Note that “fits most cars” usually means it does not contain the correct adapter; their 
definition of “most cars” apparently means “cars built after 1976 in the US” because such kits typically contain the 
1976-on adapter and the GM mid-90’s adapter but not the pre-1976 adapter.  If both service ports are the same on your 
XJ-S, look for packages of adapters that indicate they fit pre-1976 models. 

Aiken goes on to point out that, for the initial charging with R-134a, you don’t even need the high side adapter.  
Charging is done through the low pressure port and those are all the same on R-12 systems, so any kit includes a 
suitable adapter.  You’ll need to have the high pressure port adapter on there for future servicing, though. 

Interdynamics offers a kit, part number CSR-7, that includes a single can of ester oil and an assortment of port adapters. 
 It includes adapters for basically anything, including the correct adapters for the XJ-S.  Discount Auto Parts offers this 
kit for about $24.  It doesn’t include the freon itself, but perhaps more interesting is the fact that it doesn’t include the 
valve and hose assembly you need to charge the system. 

Interdynamics also offers several bubble packs of adapters.  Their part number VA-LH9 includes only the correct 
adapters for the XJ-S.  Discount Auto Parts wants only $7 for this.   Buying this package and a separate can of ester oil 
is therefore considerably cheaper than buying the CSR-7 kit above. 

There are also adapters offered with a 90° elbow in them.  Just in case you need it -- which you could on some cars if 
the R-134a fitting ended up in a position where you couldn’t jam the quick-disconnect on properly.  That doesn’t 
appear to be a concern on the XJ-S, however.