You probably think I'm crazy from the title but the compressor in my 1992 XJ6 Soverign is on its way out. There is very little suction and low high pressure, and I believe this is due to faulty valves in the compressor. My clutch is also a bit wobbly so it needs to be replaced and I have a new compressor on the way.

Now for years the AC performance has always been lackluster, especially at idle and low engine speeds on hot days, even when the compressor performance was up to spec.

Ive installed a new condenser, receiver dryer and expansion valve this spring. The condenser, along with everything else will be flushed out and the receiver dryer and expansion valve replaced again once the compressor goes in. I've never had any issues with leaks so I think converting back to R12 would give me the best possible performance.

I have my EPA 609 certification so I can purchase R12 legally, and I have the manifolds, hoses, and vacuum pump to properly evacuate and charge the system. 40oz of R12 is less than $100.

The conversion Ester oil will need to be removed from the system, and the compesssor will need to be filled with Mineral Oil. Does anyone know the proper viscosity? Also the conversion fittings will need to be removed, and the valve cores replaced.

Anyone done this?

 

hello ntl, found here, an Excel file with all the information.
best regards

 

Thanks! I did some digging and found this on Sanden's (A/C Compressor manufacturer) own website:

The 5GS is 500 SUS or 100 ISO viscosity, and I can source it easily on eBay.

I think the chart you've shown is referencing the retrofit oil for the XJ40, as it states POE which is the Ester oil that plays nice with R-134a and residual mineral oil left in converted R-12 systems.

Thanks again,
Nick

 

So my new compressor is on the way. I picked up an R12 manifold and an A/C flush canister with fittings and solvent. I also picked up a valve core tool and valve cores to replace the core that was removed on the high side during the conversion process.

My vacuum pump needed some new oil so I searched a bit online and saw Advance Auto Parts had it in stock nearby. The counter guy kept asking for a year and model number when I asked for Vacuum Pump Oil. I eventually brought up a part number on my phone from their site and his computer said they had one bottle left in stock. He finally found it in the back and rang it up. Told me it's on clearance... 5 cents! After chuckling a bit, I handed him a nickel from my pocket and left. I made absolutely sure he didn't have any more bottles left, I would've bought a few cases if he did! The price was $9.99 on their website.

I've got a new receiver dryer on the way, too, as well as some Suniso 5GS refrigeration oil which is what Sanden specs for R12. The only issue is that I could only get it in a gallon container, but it was only $30. Not crazy expensive...

I ordered a Robinair side can tap for R12 and R134a, so all I need now is 3 14oz cans of Freon-12.

I'll let you guys know my progress

Nick

 

So I've prepped the job a little, including getting the compressor drained of it's test oil, flushed with Suniso 5GS mineral oil, drained, then filled with 135ml. The rebuilt compressor did not include the low-pressure cutout switch, so I had to swap that over into one of the service ports on the compressor.

I removed the original compressor from the vehicle, as well as the Compressor-Condenser hose with muffler so they weren't hanging around in the engine bay. The Compressor-Evaporator hose was able to be rerouted into the engine compartment until I remove the battery to access the pipe fittings on the expansion valve.

I also got my A/C flush kit in, which includes a refillable metal canister, hose, fittings and air gun. I flushed the Compressor-Condenser pipe and muffler, and will flush all the other components before reconnecting everything.

My R12 arrived too! $135 for 4 - 14oz Dupont cans. A full charge (2.5 lbs +/- 2 oz) will take exactly 3 of the cans for easy measuring, and I have a spare in case it needs to be topped off. I don't plan on having any leaks with the new O-rings, rebuilt compressor, and newly-installed condenser, but if I do, I can finally use the sight-gauge! It doesn't work with R-134a but it can be used to somewhat-accurately gauge the amount of R12 in the system.

I'm ready to get everything installed and buttoned up, but I'm missing one vital part: The Receiver Dryer, which was shipped from Florida just after Hurricane Irma, and has been delayed... The good thing is that I can install everything else before getting the bottle in and installed.

I'll keep everyone updated.

Nick

 

Well there's a bit of delay with the project. The seller is sending another compressor. First off the bolt hole through one of the mounting ears on the compressor was not round. It looks like it was repaired, but was not drilled properly, so the mounting bolt would not fit through.

Also, I had to purchase a new low-pressure cutoff switch (binary switch) because mine has become loose where the plastic switch body connects to the brass threaded base.

In the meantime, I've flushed the evaporator, condenser, lines and hoses, mufflers, and replaced the expansion valve. Everything is fitted except the compressor and the receiver dryer (to prevent moisture ingress).

Can't wait to get it sealed up and vacuum tested, then on to evacuation and finally charging.


As an aside, I'm wondering if I should make a "mod" to my heater system. In 1991 (or 90), Jaguar deleted the heater control valve and vacuum hose from the cooling system. Then, in 1993, they reinstated the valve. My 1992 still has the vacuum solenoid on the heater/ac box, but with the hose and valve deleted. I'm interested in installing an OE heater control valve and vacuum tubing to the vacuum solenoid, and seeing if this would further improve A/C performance.

Nick

 

Hi Nick,

I personally think it would be worth adding back the heater water control valve. Obviously Jaguar's experiment with deleting it, with the expectation that the blend flap would be able to isolate heat from the core from air flowing through the evaporator, was a failure.

You can probably test your control panel to confirm that it operates the vacuum solenoid so it would be able to control a heater valve at the appropriate temperature settings. I will be very curious to know what you discover!

Cheers,

Don

 

Thank Don. I'm sure when these cars were new they probably didn't need the heater control valves due to fresh, tight seals on the rotary valve and flaps. But as they age, I'm SURE hot air is leaking through, and I think it can only help!

I have another issue to deal with as well. My R/H defroster flap is stuck closed, and that will definitely need to be rectified before winter comes, even if I have to manually prop it open by some means. Have you dealt with this, Don?

Nick

 

Yes, I have, though on our '93 both defrost flaps were stuck partially open. Propping it open might be difficult if yours have the same kind of fixed grate that ours had. The only way to deal with it properly is to remove the dash, but it's not as difficult as it seems. I think Haynes has the instructions but if not let me know and I'll try to remember enough to set you on the right course.

The defrost or demist flaps are hinged with integral plastic pins on each end. On their central end is a vacuum actuator with a jointed arm that attaches to the flap. I may not be remembering correctly, but I think the arm is spring-loaded so that it normally presses the flap closed. When vacuum is applied to the actuator, it pulls the arm, which pulls the non-hinged edge of the flap down to allow air to pass.

In our case, the inner hinge pin had broken off of both flaps, which allowed the spring-loaded arm to push the flap away from the opening. The broken end of each hinge pin was still stuck in its hole, so I pulled them out, carefully drilled small holes through them, then glued and reattached them to the flaps with small stainless steel screws.

In your case, I would guess that the hose may have come off the vacuum actuator or the actuator isn't functioning properly.

Sorry I didn't take photos of the process of repairing the flaps, but I had a long list of things to get done while I had the dash out. Unfortunately, the demist flaps are among the "unillustrated parts" at jaguarclassicparts.com.

Here are a couple of pix just to show you that removing the dash is no big deal:







Cheers,

Don

 

Thanks, Don. The steering wheel didn't have to be touched to remove the fascia?

I'm hoping it's a simple vacuum supply problem and not a mechanical issue with the flaps or diaphragm. I do remember hearing a sharp "click" noise from the defroster area once in a while when starting the car. We'll see.

If the dash is opened up like that, it would definitely give me a good opportunity to clean and inspect the Heater/AC unit.

-Nick

 

Nope!

Of course, you'll want to tilt or extend it as necessary for more clearance to pull the instrument cluster out.

Cheers,

Don

 

So I finally got the bad remanufactured compressor back out and ready for shipping. The new remanufactured compressor is in, along with it's 135ml of 5GS oil and a new binary (low pressure) switch.

The original switch, which is quite small, is a Santech MT1064 and costs roughly $50-100 depending on retailer. The black plastic base is bonded to the brass fitting, and has proven to be unreliable. The original and a replacement both failed here, and would allow refrigerant and oil to leak. One even blew right off, causing a catastrophic loss of R-134a and oil.


Original Style Santech switch.

After doing some research, there are many alternatives to the OE style binary switch. I chose a Universal Air Conditioning branded switch, which has a much larger base, and performs the same low-pressure cutoff for compressor protection against low refrigerant. The model number is 4086C. I ordered it from Amazon for $10.95. I feel that with the much larger base, there should be no issue with it coming loose over time.


Universal Air Conditioning 4086C. Santech also makes a similar model.

I took a picture of the tools and parts needed for this conversion:



Here's a pic of the old vs. new pressure switches:


Old Pressure Switch

New Pressure Switch

There were no clearance issues with the larger switch. Once everything was installed, I evacuated the system for a couple hours, then charged with 42 ounces (2.5 pounds) of Freon 12. It's awesome to have a working sight glass and having an "eye" into the system. In the future, I can now easily check the charge level and adjust as needed until there are no bubbles visible in the sight glass.

Hope this helps someone who might be considering reverting their Pre-93 car back to R12. The same would apply to XJS cars, as well.

I can already feel the advantage of the R12 over R-134a already, when cooling the heat-soaked interior after parking in the sun. The cool air comes faster, and at a lower temperature than I ever experienced with R-134a, even at it's prime. There's a side benefit other than the increased thermal transfer capacity of R12, and that's the lower compressor pressures, which could potentially save fuel and reduce strain on the engine. I couldn't be happier, and I've gotta say it again: It's really cool having that working sight-glass!

-Nick