I have a 96 XJS with the AJ16 engine.

I was enjoying cold air through my air conditioning...until I did not last night. I thought I might just need to add some refrigerant, since admittedly, I have had a slow leak over the years.

The refrigerant did nothing. Compressor kicked in, but only hot air blowing through. The high side got to 300, the low side would eventually bottom out. So I have something wrong on the low side.

On top of that, when I wasn't charging, the compressor would make a grinding noise, rythmically. When I started charging, it immediately stopped.

I suspect the compressor is finished? The compressor is original. Belts have been replaced before, as has drier, expansion valve and condenser. I see I need a Sanden SD7H15 compressor. Anything in particular to look out for?

 

See my answer and diagnosis chart on the Jaglovers forum.

 

Thank you. I really appreciate this.

Now to figure out where the blockage might be. Feeling the hoses, I couldn’t locate a cool section.

Any suggestions?

I suspect I’ll disconnect hoses and blast compressed air from each end? Can I blast air from the low pressure hose back through the evaporator and expect to feel it at the disconnected expansion valve?

Then from the disconnected expansion valve joint to the disconnected drier end?

then from the other end of the drier, through the condenser and out at the disconnected hard pipe by the high pressure port?

Will that work? Is there a certain side that’s better to flow in to?

 

I would start with the expansion valve and go from there. Clearly the compressor is capable of making pressure. Once you have the system discharged, then you can air test each component individually for flow.

 

Taking my last kid to college tomorrow. Luckily there won’t be any competition for the spare car…with AC. It’s been absolutely brutal here in DC.

I am hoping this weekend will be a cooler day to
take everything apart.

I have replaced the shrader valves in the past. They are not original to the car, but one has clearly given way at the low side muffler. That couldn’t be a coincidence, could it?

 

It's possible. They are a rubber ball type check valve, it's possible one has disintegrated and put bits throughout?

 

Vee,

Good luck with your investigations. Just reflecting on your comment about the noise from the compressor; some years ago, a friend of mine had an issue with a noisy compressor and no cooling. He had normal high pressures but nothing on the low side. It eventually transpired that the oil had gone from the compressor into the refrigerant. It then blocked the evaporator which caused the low pressure to drop out.

Just a thought.

Cheers

Paul

 

So here's where I stand, I'm interested in theories.

I depressurized the system, and it wouldn't fully depressurize. It went to a slow hiss for quite some time, very strange.

OK, so I took some of the connections apart, including the o-ring at both schrader valves. I blew compressed air from the low pressure port and it blew out at the disconnected line at the TXV without any obvious obstructions.

I did the same from the high pressure port to the dryer.

Then through both ends of the drier.

I also pushed air from the output side of the drier to the disconnected high pipe at the TXV.

Nothing indicated any blockages.

Did I miss my opportunity to blow air through the evaporator when I had the TXV off? I never did it. Would it have helped? Do you think it might have been useful? I wish I had blown air back from the low side, through the evaporator, and into the high side. That's likely the only side that could have had a blockage?

In any case, new o-rings everywhere. New TXV and new drier. This time with a glass viewport! It always seems so random.

I vacuumed out the system for about 20 minutes, then closed the valves and left it in vacuum (with the pump removed) overnight and started charging this morning. None of the needles moved at all. Held vacuum perfectly.

I filled up the system with a calculated 968g of new r134a (book calls for 950g +/-50g) and everything seems normal again.

I did find one badly mangled o-ring at the outlet port of the previous drier. I clearly pinched that oring when I replaced it last time. It might explain the s-l-l-l-l-o-o-o-o-o-o-w refrigerant leak I had. This time I lubed up all orings with refrigerant oil before reinstalling. I don't think I had done that before.

So no obvious signs of blockage...except for the unchecked evaporator. If I have problems again, I'll keep what I have and just take it apart enough to blow compressed air through the evaporator through the removed TXV ports.

 

Could the distorted oring have been partially blocking the line?
The fact that it works normally now tells me that you somehow removed whatever blockage you had. Based on your description of the discharge, something was obviously blocking the flow. My guess is something in the receiver dryer was moving to block passage. When you blew air thru it, it moved out of the way.
Glad you eliminated the problem, whatever it was.