More Air Conditioning Questions

[northwindone]

When I bought my 2003 Vue in 2019 it didn't have working air conditioning. In the spring of 2020 I finally got tired of sweating during my commute here in the desert and decided to fix the AC. I replaced the expansion valve, drier/accumulator, and then any of the o-rings on anything I touched including the solid line joint near the top of the engine bay near the low side port I believe. I vacuumed the system down as far as my vacuum pump would go and then left it sitting for 24 hours to make sure there weren't any leaks.

I added UV dye and PAG and charged the system with the correct weight of R134a. The systems worked great and was cold even at 110+ until last week when I found I had no AC (a few days after I lost A/C on my F-350 ). Found the clutch wasn't kicking in either. I pulled out my gauge set and found I had 0lbs. I took a partial can and tried to add a few oz and found the coolant was leaving as soon as it was added through that rigid joint I mentioned earlier that had a new o-ring installed in 2020.

My questions are as follows -

1 - Did I possibly use the wrong kind of o-ring on that joint? Haven't taken it apart yet, but I'm thinking I used a standard green HNBR o-ring. Should I have used one of the ones with the metal ring attached to the rubber? Finding parts diagrams of the AC system seems impossible, found one showing that o-ring with a notation, but the image was on Pinterest (which I find extremely annoying) with no useful information on the origin of the diagram and where it was stolen from.

2 - I live the desert with very very low humidity and it has only been evacuated of coolant for 2 or 3 weeks, should I still replace the receiver/dryer just to be safe?

3 - Considering there was PAG in the system from before I bought the car, then I added a bit more a few years ago, should I add more? I don't want to starve the compressor of oil, but also don't want to add too much.

[fdryer]

Don't add any more pag oil. Unless your system lost a great deal of refrigerant oil from a catastrophic rupture releasing refrigerant, oil and dye all at once, each part replaced has a specified amount of oil replacement poured into it to balance the overall system amount. Since oil circulates freely throughout a system, liquid refrigerant forms after the compressor condenser coil, travels to the thermal expansion valve where the suction side of the evaporator allows refrigerant to expand back to its gaseous state and draw heat from the cabin. Oil becomes a mist to travel back to the compressor for lubrication. The compressor, condenser and evaporator coils have the bulk of pag oil while accumulator requires less than an ounce.

Usually, fittings with the single bolt use the green O-ring. The suction side and discharge side fittings use the metal washer/inner black flat ring. The metal washer is aluminum and only used once as its crushed when bolting fittings together for a seal while the flat rubber O-ring seals against pressure. I think both ate not lubed with pag oil but all other O-rings need lube for proper sealing.

One of my repairs required a new discharge hose and the fitting going to mate with another hose appeared ok. The fittings leaked because corrosion occurred on the old fitting despite a new flat washer/O-ring. I carefully flat filed the corrosion off the old fitting so a new flat washer would seal. It worked otherwise I would have to replace the older hose and maybe chase fitting leaks. Post a snapshot but beware, thumbnails are restricted to less than a megabyte of file size. Use any image app to resize files greater than a megabyte. Virtually every cellphone and digital camera creates multiple megabyte image files that won't be accepted as thumbnail attachment to posts. Jpeg works well here.

With an empty system, leave it alone until repairs are made. Any residual refrigerant keeps air and moisture out. Major ruptures only needs to be plugged until parts are replaced. The drier is fine. A longer evacuation, presuming you're using an electric vacuum pump will pull air and minute moisture out of the system, including the drier. An hour is fine for evacuating a system. The low humidity where you are helps to some degree.