Hi Everyone,

I am at my wits end. I have a 1989 Jag XJS and I have converted it to R134a. I replaced the condenser, all hoses, all O-rings, drier, expansion valve, etc. Basically, everything is new except the evaporator (I had it flushed out at a shop). I cannot seem to get the a/c to blow less than 68 degrees Fahrenheit from the center vent. It blew less than that before I started this journey. It is reading 45 lbs on the low side and 375 lbs on the high side it is currently 80 degrees outside. This happened before and I reclaimed the refrigerant and started over. This is making me nuts. I have been doing this in the garage and maybe the heat from the engine is having an impact? I am at a loss. Any help would be appreciated!

 

The high side pressure is way high. Are those pressures at idle or what rpm. 12 ozs of 134a is equal to 16 ozs of r12. If that high side reading is correct i am sure the safety switch is turning off or cycling the compressor. Did you do a thorough vacuum of the system before adding freon. That is crucial on a conversion. The lube oils are not compatible from r12 and r134a.

 

The high side pressure is way high. Are those pressures at idle or what rpm. 12 ozs of 134a is equal to 16 ozs of r12. If that high side reading is correct i am sure the safety switch is turning off or cycling the compressor. Did you do a thorough vacuum of the system before adding freon. That is crucial on a conversion. The lube oils are not compatible from r12 and r134a.


Yes, I vacuumed it down to 29 inches of mercury. It is at idle and 3000 RPM. I flushed the evaporator and everything else is brand new. I put 34 oz in the system. Didn't get below 70 degrees inside. I am aware of this (what you have said above) and why I am frustrated. I reclaimed the freon and vaced/charged again. No change.

 

I am only familiar with the 1996 cooling system. I am assuming it's all similar, regardless of the refrigerant, so I offer the following:

There could be a blockage in the system. The dessicant ***** in the drier can break free and get stuck. If you de-gas the system again, you might want to see how much of the tubing you can take apart and blow as much compressed air/vacuum as you can depending what part of the system you're in?

Have you replaced the expansion valve? Usually a cheap part to replace, and pretty easy. If you haven't, it could be the source of the problem.

After that there's also the clutch pressure switch, which isn't a part that is known to go bad. You can test it by running the system, unplugging the harness and jumping the two contacts. If you hear a click, its most likely working.

That's all I got. There isn't a whole heckuva lot to check. There's the compressor, condenser, evaporator and the drier. Assuming it's over pressurized and that's not the concern, the only thing left is the control panel may be defective in some way? For the 96, you can have the AC blow warmer on the grilles than at your feet. Could that be stuck? Could the control panel be stuck at a position where it cannot direct more cold air through the evaporator? Is there a thermostat that automatically controls the air temp? I leave mine in manual.

 

I agree. 375 psi on the high side is WAY out of spec! Find what's causing the high pressure first.
You mentioned 34 oz but I don't know what the refrigerant capacity is for that model and year of Jaguar.

One thing I "might" suggest? I don't see how many miles are on the car and I don't see that you changed the compressor either?
Possible you need to change the AC compressor? The car is 34 years old now.

Can you let us know the type and quantity of oil you put in when changing to R134a?
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I changed everything but the evaporator. Condenser, compressor, all hoses, expansion valve. I had the evaporator flushed at a shop. I put 8 ounces of PAG100 oil in the compressor plus an additional 3 ounces in the rest of the system.

 

The R134a capacity is 34 ounces (80% or R12 capacity).

 

ALL Jaguar A/C systems until X300 and X100 are weak at best with 134a conversions.

You will NEVER be happy with the interior temp in the Summer.

 

You know, I live in Kansas and it gets above 100 in the Summer. I retrofitted my XJ-6 and it blows 45 degrees at the center vents. it is black on black but still is very comfortable inside. My XJ-s used to blow around 50 at the vents before I changed everything on it. I believe that the shop that did the conversion on the XJS never vaced it down properly before charging. I think that was why it never got as cold as the XJ-6.

 

Guys, I did have to put a 35 degree bend in the pipe coming off of the condenser that runs to the high side hose on the compressor. I used a tubing bender. I had to do it to fit around the trumpet on the airbox. Maybe that is the cause?

 

Check temp differential on both sides of the bend? It could act as a 'orifice-tube' in the system?

 

Just tried that! Great minds think alike! There was no difference both sides were about 160 degrees. However, I did note that the high pressure pipe coming off the compressor (the one with the muffler and the charge port) was around 190 degrees. After that it dropped almost 40 degrees. I think I may have found my blockage!

 

Do you suspect that the AC muffler is the culprit? I've always wanted to see what was inside that thing.

If you happen to remove it, would you consider cutting it open and posting the pics?

 

I'm thinking it might be. Trying to find a new one and not having much luck. I have a borescope and I am going to try that to see the inside. May be too big though.

 

So, I found a new muffler and installed it. Replaced the expansion valve (again). Flushed the bejesus out of the evaporator. Vacced down and recharged. No change. Can't get below 68 coming out of the vents.

 

I have a similar issue, but it might not be the same.

I thought adding some refrigerant would solve the problem, so I hooked up the manifold and added a can. The compressor was making weird noises until I opened up the manifold and started adding refrigerant. Another forum member suspected I had a blockage somewhere. The high side managed to get too high, to about 325, where the low side would drop very low. So I suspect that the blockage is at a point before the muffler, where the low port is.

I plan on depressurizing the system and disconnecting as much as I can to see if I can either blow compressed air in, or try to attach a vacuum and suck something out to clear the blockage?

I bought a new drier and expansion valve. I was gonna buy a new muffler hose, but now I think I'll hold off on that.

Did you take pressure readings using a manifold? You can get them rather affordably from Harbor Freight or perhaps Amazon. For me, it confirmed that the compressor was still doing it's thing, so I know I don't have to replace that. I added UV dye as well, but nothing has shown up.

 

Best of luck on finding the muffler. Everyone has it listed as "backordered". I found one, but I was lucky, on that part at least. I vacced and recharged again. Now, I am getting 61 degrees at the center vent. I dropped it off at a shop this a.m. to see if they can find what is wrong with it. I did the R134a conversion myself on my XJ-6 and it is blowing 45 degrees coming out the center vents! I did use manifold gauges. I have my own reclaiming machine and vacuum pump.

 

There is a common problem with the filter/drier on these cars and the XJ40/X300.

The desiccant 'beads' break loose from the container and spread throughout the system up to the expansion valve.

If you backflushed the evap core then you would have noticed if there were loose desiccant beads present in the system.

 

So, the mechanic is stumped. He thinks that it has something to do with the A/C condenser fan not coming on as it should.... He wants to trace the wiring back to the "problem". I'm going to do that myself. More to come...

 

On the way back from the mechanic's shop, the compressor "gave up the ghost". It lasted....a week! I ordered the Fen Air Sanden conversion kit as mentioned on "Living with a Classic". It is supposed to be better than the A-6 compressor. I also suspect that I shouldn't have used PAG oil even though I replaced every component, apart from the evaporator. The kit is coming from England so, it will be the end of summer before I can report back.