I have a 97 850 turbo, with R134a. On a recent trip, the ac compressor went out—it wouldn't rotate.

I replaced the compressor with a used one from a salvage yard—a Zexel. I also replaced the dryer and the orifice tube. I added 3oz of PAG 100 oil into the back of the compressor.

Before I installed the new orifice tube, I flushed the system with a flushing compound in a pressurized can. Then I used compressed air to rid the system of the compound. I didn't have an unlimited supply of compressed air so I might have left some liquid in the evaporator or the condensor.

I assembled all the parts and put in a new orifice tube. I checked for leaks, vacuumed the system and filled with nitrogen to 100psi. No leaks were noticed.

Then I evacuated the system to 29 plus inches of mercury and held it for an hour. No leaks.

Next, I engaged the compressor clutch and added a can of R134a that also had 2 1/2oz PAG 100 oil and a compound for stopping leaks. I emptied the can; the air from the dashboard duct was around 75F, down from 100F. The outside temperature was around 90F. The can emptied in about 5 minutes and was very cold while I was holding it. The engine was idling the whole time at about 750rpm.

I connected a 3oz can that had 1oz of R134a, 1oz of ICE 320 Performance Enhancer and 1oz PAG 100 oil. I put most of the contents in the system—about 3/4ths, and then started to add a 12oz can of only R134a.

This can did not get cold while empting into the system, it took over a half an hour. I checked the air temp from the dashboard duct periodically while this can was empting into the system. The air temp wasn't changing and as the can emptied, the air became warmer so there was almost no air conditioning effect on the air. At this time, my low side pressure was about 45psi. Near end of this filling, there was a release of mist and a hissing at the back of the engine, near the turbo, like a pressure relief valve opened. I stopped filling and turned off the compressor, (I had the compressor clutch engaged by bringing a wire to it from the positive side of the battery).

So, there I was. System appearing to be full—maybe overcharged—and no cold air at all. I left it overnight to think about this problem.

In the morning, I evacuated the system and left the vacuum pump running for 20 minutes. Then I let it sit for 40 minutes and turned on the pump again for 20 minutes. Then, I let it set for 40 minutes. The vacuum held so I started again to add R134a with the clutch engaged and the engine at 750rpm.

The can was cold while emptying into the system and the pressure climbed up to 45psi on the low side. The temperature of air at the dashboard duct did not change, it was around 100F with an ambient temp of around 90. As the can was filling the system, I felt the lines into and out of the evaporator. They were at room temperature, but, those same lines at the front of the car near the low pressure inlet, were hot—both lines were hot to the touch.

I disengaged the clutch and turned of the engine and removed my filler hose from the port.

What do I do now?

The compressor was pumping during the charging procedure because with the clutch engaged the low pressure side was 45psi and with the clutch not turning the compressor, the pressure was about 90psi.
All I can think is that the orifice tube is not decreasing the pressure into the evaporator or I'm getting liquid in my compressor for some reason that I don't know.

I moved the dial that directs the air to the floor or the windshield thinking that perhaps a vent is not working properly but all appeared to be working correctly—I could feel the air flow. Maybe there is a problem with the vent directing the air from the evaporator?

I just don't understand. I really could use your help.

 

You may have some residual crap stuck in your new orifice tube. That happened to me when I put in a wrecking yard compressor in my old Explorer. It sounds like you did everything right, but it doesn't take much to clog the orifice tube to the point of non-functionality.

Side note: Since I thought the old Explorer's AC was totally shot, I experimented and filled it with air duster instead of R134. It works great and is cheaper and supposedly environmentally safe.

 

So, I did everything again.

I opened the system and blew compressed air through the evaporator and condenser and the lines.

I didn't blow through the suction and discharge lines on the compressor because they are very difficult to remove and also because when I stuck a Q tip in the lines, it did not come out with any dirt on it.

I reassembled the system using a new dryer and orifice tube and drew a 29 + inches of mercury vacuum and held it for a half an hour.

Then I recharged the system with 1 12 ounce can of R134a. The dashboard duct air was lowered from 100F to 75F and the suction pressure was 30psi and rising. I disengaged the clutch at 50psi.

I assumed the orifice tube was clogged and that was causing my pressure to continue to rise. I took out the orifice tube and looked to see if it was clogged.

It had only a few grains of "dirt" on it and it wasn't clogged.

I talked with a home and commercial ac man who said I should just leave it run. When the system cools down after running for a while, the non-condensables in the system will collect in the dryer and the pressure will go down.

I installed a new orifice tube, put everything together and vacuumed the system. I held the vacuum for a half an hour and them put a 12oz can of R134a into the system. The pressure got up to 40psi and stayed there. I let it run and the pressure continued to stay in the 30-40psi range.

I turned the engine off for a few minutes and when I restarted the engine and engaged the ac clutch, the pressure was around 40psi and was climbing. I checked the duct temp. It was 75F.

Then I heard a hissing noise and saw a mist on the back side of the engine. It looked like a pressure relief valve opened. The suction pressure then was around 50psi.

This happened once before during this ac compressor replacement job but never before this.

Is there a pressure relief valve? Where is it? And, is this normal? I thought the high pressure switch would just disengage the compressor clutch (please note that I have been using a wire from my battery to activate the ac clutch so the high pressure switch would be circumvented during this procedure).

Any ideas what the the mist and hissing was?

Thanks for your help.

 

A/C systems do have an overpressure relief valve. I have no idea where they are on the Volvo. I heard once that after a pressure valve has been "sprung", it loses its strength and releases at a lower pressure level. maybe replacing it would help, but you should be getting SOME cooling even at a lower pressure.

I'm stumped. Maybe one of the new parts is defective.