So I've just reassembled the XJ8 after having the engine out to fix a multitude of oil leaks not the least of which was the infamous galley plug on the back of the block. Everything works now EXCEPT the air conditioning. I pulled a vacuum, it held fine so I started to try and charge it back up but it wouldn't draw any refrigerant. Hooked up the high side and its floating around 100PSI on both high and low sides, which I'm guessing is about what the static pressure is in the refrigerant can. Compressor clutch IS engaging. There are no funny noises. Fan blows strong. I didn't do anything with the compressor other than disconnect the pipes from the back of it and reconnect them. Wondering what I could have done to kill it? It was working perfectly before. The system was opened for several months, but its been indoors and this is a dry climate so that's never been a problem before. The JTIS seems to be written for the professionals in the shop who already know what they are doing so its been of little help. Any insight from the A/C gurus appreciated.

 

Hi Phil,

This is a wild guess and may not apply to your situation, but I ran into a charging issue while helping a friend. He had purchased the newer R134a cans that have a "self-sealing" valve. We discovered that these cans do not work with the older type of can tap valves designed to pierce the metal plug in the necks of the old style cans.

On the old-style cans, you screw the valve all the way down to pierce a hole in the plug, then turn the valve all the way back to allow refrigerant to flow.

With the self-sealing cans, the needle-point tip on the old-style tap pierces through the rubber seal but seals the hole it creates, preventing refrigerant from flowing out of the can. When you retract the tip to allow refrigerant to flow as you would with an old style can, the rubber seal simply re-seals both the can and the small hole created by the needle.

The self-sealing cans require a new type of tap valve with a blunt tip that depresses the seal in the can to allow refrigerant to flow while the tap valve is fully screwed down. Retracting the valve allows the can to reseal so you can more easily save partial cans (and prevent left-over refrigerant from leaking into the atmosphere). You can buy these tap valves at the stores that sell the self-sealing cans.

I hope your issue is that simple.

Cheers,

Don

 

You may have something. My hobby is old cars (R12) and I've rarely had to charge my modern daily drivers. I had bought a case of R134 more than ten years ago and used my last can last summer so I did have to go to the store yesterday to buy some new. I thought it was flowing because I unscrewed the line to see if any would bleed off and it did but maybe its not flowing enough to do any good. I'll switch out the tap and see what happens.

 

Well, sadly, having the adapter didn't help. Still won't draw refrigerant and showing pretty much equal pressure on both high and low side. Wish I knew more about the A/C system as I hate to jump to ordering a new compressor, but that's what it seems. How does a compressor go bad just from sitting on a workbench for several months? Or what could one possibly do wrong in reinstalling it? Is there any sort of safety bybass around the expansion valve that kicks in somehow that's been triggered?

 

Modern refrigerant recovery/dispensing machines don't need the engine running or the compressor operating at all.
They simply recover, vacuum and then you set the machine to dispense the refrigerant charge.
The machine charges the system and shuts off when the specified weight has been added.

If there is a blockage, the machine will sound an error tone if the charge is not dispensed.

Ask around to local shops to see if they will evacuate and charge your system and how much they charge??

bob

 

Well before I spend any more money, I removed the compressor to inspect it. It seems to be working. Or at least I can put my thumb over the ports and it'll make good suction or pressure while turning the shaft slowly by hand. Another thing I had discovered last weekend after the attempt to charge was that later I returned to the garage and found a large puddle of condensate on the floor that had drained from the plenum. Wondering if it immediately iced up the evaporator? I was kind of working under the assumption that the only thing that would cause the gauges to show equal pressure on both sides was a compressor failure, but that appears to not be the case. What else can cause there to be equal pressure on both high and low sides if the compressor is working OK?

 

If the compressor is pumping, there will be a pressure difference. If the compressor valves are blown, the compressor can be turning but unable to pump. Another indication obviously, is that the fat line gets cold, the skinny line is warm/hot. If there is a PD, then there will be a temperature difference (Td).
Perhaps it’s a gauge or manifold issue.

Ltd

 

I wondered if my gauge set had failed on me somehow but I'm not really sure of procedures to test it. The gauges themselves seem to read correct pressure but there's valves and stuff inside the manifold that I suppose could wear out or go bad from sort of infrequent use. I did try to feed the first can directly into the low side port without the manifold and gauges, kinda like those DIY recharge cans, but without success.

 

Just updating in case it helps anyone at the risk of my own embarrassment. So first issue was my low side port quick coupler adapter was not fully depressing the schroeder valve. Apparently the can static pressure was enough to overcome the valve by itself at least enough to raise the system pressure so the compressor clutch would engage, but it wasn't open to flow so all I was reading was static pressure. I bought a different type of low-side port adapter with a knob for adjustment so that I could put it on and then turn the knob to open the schroeder valve. Once it got enough refrigerant in it, it started showing a pressure differential. But still not cooling well and after much grief and agony, I gave in and had somebody else look at it. Apparently I hadn't gotten a heater control valve plugged back in and thus it defaulted to heater full on despite the dash display showing it was in max cooling mode. So the darned a/c was just trying to fight the heater the whole time. Blowing 42 degrees now.

 

Heater vs evaporator= HEATER ALWAYS WINS!!

bob