Went to a car show yesterday and boy was it hot! Our Jaguar is equipped with air conditioning but it doesn't work. Clutch never engages, fuses all good, zero pressure on both sides. Previous owner suppled service records indicate the system was changed to accept R134A. All the components look to be original so I'm thinking all they did was swap out the test port fittings. Anyway, where is the best place to start in diagnosing the issue(s)? I have the Delanair manual so the schematics are available to me. I just wanted to get some good advice on where to start. Thanks!!

 

You say it has zero pressure both sides, so I assume you have gauges, and that you've determined the system is completely empty. Your car should have a high side low pressure switch, so the compressor clutch won't kick on until there is some pressure in the system. First thing I'd do is pull a vacuum on the system, and see if it holds. It should hold vacuum indefinitely. If not, you need to find the leak(s). If you're lucky, there will have been dye in the system and it will show up under ultraviolet light. If it holds vacuum with the gauge hoses installed I'd change both Schrader valves at the hose attachments since that is a very common leak area, and you can't tell if they are leaking with the hoses attached. Since you don't know how long the system has been empty, change the receiver drier as it is likely full of moisture.
Once you've found and fixed any leaks, repull a vacuum, and introduce R134a. Since you live in the US and can buy R134a in 12oz cans, introduce the first can without the car running. One 12oz can should be enough to allow the compressor to kick on. Fill the system to spec from the low side, engine running. A link below to the R134a retrofit document has the specs.
http://jagrepair.com/images/Electric...t%20Jtp425.pdf

 

Also, here is a link to the wiring diagrams for your year of XJS. They will help a lot if you have electrical a/c issues.
http://jagrepair.com/images/Electric...Electrical.pdf

Jon

 

While it's down disconnect the line from the top of the expansion valve and inspect the screen. Mine was packed with a lint type substance.

 

I'm assuming you have the A6 compressor, and Jaguar used a retaining plate for the hoses to the back of the compressor that was a bit thin and can bend if the bolt is over tightened. Then the hoses are not held tight against the compressor and can leak.

When GM cars used those compressor in the 70's, the plate they used was about twice as thick as the Jaguar one. If you can find one, use a GM plate or make your own out of 1/4" thick steel and that won't bend.

 

I pulled vacuum down on the system to around 28 inches...according to my gauges. It held this vacuum overnight and is still holding. I can assume/guess from this that there is no leak or that there is a blockage before a leak point. I'm going to follow the advice given and replace both schrader valves and the receiver/dryer before pulling vacuum again and introducing some refrigerant. Stay tuned and thank you all so very much for the advice! Maybe a new expansion valve too. Current one looks a little crispy.

 

FYI: When undoing the expansion valve you MUST support the heater pipe side fixing against the undoing torque or you will tear off the copper pipe from the heater.

 

Just a side note.
If the original R12 hoses are there, then over time R134 will leak out of the system through these "R134 permeable" hoses.
If my information is correct, then when the coolant is changed, the hose must also be changed.

 

I did see if the system would accept some refrigerant and it did but evidently did not satisfy the pressure switch. I emptied one 12 oz. can and started another. Still no love from the compressor so I jumped 12V to the clutch and watched my gauges. Evidently the compressor is bad as it will not pull down the low side pressure at all. After adding two 12 oz. cans the low side pressure is close to 100 psi and the high side is about the same. I also see evidence of the hoses leaking so I'm pretty sure they are original. So....getting the a/c to work is gonna require a new compressor, hoses, receiver/dryer and expansion valve. Probably need to flush the condenser too. Haven't really decided if it is worth the trouble and removing the expansion valve make me nervous as I don't want to break off the evaporator nipple.

 

As long as you backup the evaporator connection with a wrench, it shouldn't be an issue to remove the evaporator. Avoid a rebuilt compressor. There are brand new compressors made of aluminum available that will bolt in and replace the old Delco unit. Exact fit.
Rock Auto has them, as well as a couple of the hoses and expansion valve you'll need.

Jon

 

I was looking through the previous owners service records and found that he paid $1040.00 in 2020 to have the a/c converted to R134. The shop added the different test ports, replaced the reciever/dryer and flushed the system before adding the new refrigerant. Seems he got ripped off.

 

We can help you with that one. Working AC is totally worth it.

Are you adding oil when you are charging? I am a big fan of as it comes with UV dye to help you find the leaks.

You can make your own hoses. - when you're done either save it for the next project or sell it for $75.

You can buy hoses and fittings from ColdHose. Doing it yourself means you know it's done right. You can also pick up receiver/driers and expansion valves there too.

Good advice has already been given on removing the expansion valve - make sure you follow it.

 

Thanks to everyone for the advice! I'm still mulling over justification and convincing my better half before going forward. I still need to confirm everything is working electrically. It seems everything is in order. My vent servos switch air flow correctly. I have not checked the air temperature sensor(s). I have checked the related relays using a power supply and digital meter but I have yet to see if power is getting to the high side low pressure switch. I figure total cost in parts will be considerably less than $1K doing it all myself and going the new compressor instead of a rebuilt unit.

 

If I decide to replace the compressor, hoses, expansion valve and receiver/dryer, shouldn't I flush out the condenser and evaporator?

 

Yes. I got one time use flush kits at the local auto parts store. Some also rent the flush tools, and you buy the flush liquid.

Jon

 

If you have pressure in the system and the clutch is not engaging, take a close look at the pressure switch on the back of the compressor. It is insulated electrically by the O ring, and only makes contact with the snap ring that holds it in place. I have had a system not work because of that. I wiggled and moved the switch a bit and it made contact and the system then worked.

As a test, you can ground the wire to the pressure switch and see if the clutch engages.

 

I cannot even see the pressure switch or the wire going to it. The cruise control bellows assembly is pretty much covering it up.

 

Sounds like you should be able to fix it. and make it better then new. I especially like the DIY, Hydraulic crimper thats pretty cool in itself, and you'll be able to upgrade the lines as well. I've never really seen the issue of 134 escaping through the lines. As most AC systems always had something go wrong with them, and they had to be recharged after the repairs anyway. Good Luck, I will surely do mine, as My car is all Black, and I live in Arkansas so it gets pretty dang hot. Oh, and I've become a AC sissy as I've gotten older. LOL.

Jack