A/C Diagnostics

[rbodor3]

155k miles, S60. 

Spring 2014 had the system completely emptied for other work, and accidentally ran it dry. Replaced compressor, drier, expansion valve, and had it refilled. Cold air all summer.

First hot day 2015 no cold air. Checked with the manifold yesterday.

Ambient = 60F

Static = 50 psig

Idle Suction/Discharge = 25/100 majority of time, but would randomly peak to 45/200 (although I never saw compressor disengage)

 

Compressor engages just fine. I vacuum pumped the full system for 30 minutes, recharged with 12 oz, and results were nearly identical.

How much refrigerant do I need to add? 

Should I, and how do I, evacuate the oil that my R134a cans add each time? I've added/vacuumed 2-3 times and believe there's too much oil in the system.

Is this expansion valve, or drier problem? I ran all Spring 2014 no problem, so I suspect foreign material clogging expansion valve doesn't make sense now. But what could've clogged the drier?

 

[Fran9690]

Isn't the spec for this system 2.17lbs if I'm not mistaken? So 12 oz is only partially charging the system. 16 oz is a lb, so you need close to three 12 oz cans to fill it up. As far as I know, regular R134a cans shouldn't have any oil in them? The bulk 10 lb tanks we use at my shop don't, we have to add oil before we charge the system. If it ran last year okay but not now, I suspect you have a leak. 

[rbodor3]

More diagnostics completed yesterday:

Ambient = 71F

Static = 75 psig

Idle Suction/Discharge = 25/120 most of the time, with random spike to 50/200 (again, compressor never disengaged).

I suspected a leak as well, but it held vacuum without any leaks for over (10) minutes. I do hear whistling from the expansion valve nearly all the time, which would seem indicative of low charge.

I'm concerned that I will charge it fully, and the higher pressures will expose a leak on the high pressure side (since low pressure must be good up to 75 psig since it holds that static pressure). Then I will have to reclaim, and recharge.

[Flukey]

Simple answer to me, and I have dealt with this stuff before is to re-claim and re-charge with the proper amount of 134. But while and after under a vac for a minimum vac for at least 30 min. you should charge the system with nitrogen and monitor the gauge for at least an hour to see if you see a drop in pressure. If no pressure drop is present, then vac the system again for a minimum of 30 minutes before re-charging with the proper amount of refridgerant.

Importantly,is to dis-connect the low side connector near the passenger side firewall and jump the poles with a paper clip or or a wire when charging with either Nitro or 134. This will make the compressor suck in whatever you are attempting to charge with. If you do not follow this step, the system will not recognize the pressure in the system..If you do not follow these steps you will have no idea of how much 134 yo have in in the system. DO NOT ADD ANY MORE OIL. There, this took up 2 beers of my time, I hope it helps ya.

[rbodor3]

I vac'd the system, then re-charged without adding oil. I didn't measure oil that was removed, since MIDAS did the re-claim for me.

When I re-charged, I used non-oil R134. Ran great, cold, maintained pressure, for about (3) weeks. Then I started getting some squeal from the compressor, when cold, and air was only cold when RPMs were up.

I added about 3-4 oz of oil, which made the squeal from the compressor better, but it's still apparent. Air is cool at idle, but cold with RPMs up. 

 

[Fran9690]

Sounds like you got a slow leak. Add dye to the system and check for leaks with black light. Condenser is very common on P2's. I've also seen the suction line going to the compressor rub through on the air guide.