A/C Refill questions

[Matticus]

I would think the oil would still be in it. I replaced the compressor a little over a year ago. The air is great now.
So to answer directly, I wouldn't add oil. To give some advice, I would check the pressures on the hi and low side first. They can tell you if the problem is with the refrigerant level or with the compressor. Refrigerant only disappears when there is a leak. Since it is a sealed system, just removing it and reading doesn't accomplish much.

I don't think any a/c system is 100% sealed and can/will lose refrigerant overtime without having, what would officially be termed, a "leak". As far as adding oil, if I evacuate the system, seems that oil would need to be put back in since I just evacuated the system

 

[1955moose]

I agree, if the complete system is 100 percent pressurized, with no leaks, in a perfect world it should be like your fridge at home, never need a bit. But we're talking automobiles, with places to possibly leak. Add to that vibration, weather, and other things, and you can get some leakage. Hook up your gauges, check the temperature charts for appropriate readings at that temp, and go from there. You could buy an evacuator from a tool store, or maybe harbor freight. Handy to have. I did like you, empty system, read sticker, and usually threw in three small cans, 12 ounce each. Ac was nice and chilly, done! I unlike the others don't get too technical. If it works for me, I go for it. Almost 50 years later working on these heaps, why change.

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[1955moose]

Well I wanted to add one more thing. Most if not all Ac specialists recommend replacing the pag oil that was evacuated. The big question is how much oil did you evacuate out with the freon? The comments online say replace what you took out, common sense, if your sucking out everything, freon, oil, water, gunk, makes sense if 3 to 3 1/2 ounces of pag46 came out, that's the amount that I'd add along with the freon. Any of our Pros want to comment on the oil replacement?

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[sesmith]

No, you are not sucking oil out. Each part of the system has a certain amount of oil in it. There are specs that say, for instance, if you replace the compressor, it has a certain amount of oil in it, and you have to add that much back into the system when you put the new compressor in it. The issue comes when you remove the refrigerant. If it's done slowly with an ac machine you lose very little, if any, oil. Most ac machines allow you to measure any that comes out, so you can put the same amount back in. If you just crack a line, who knows how much oil leaks out.

When you pump the system down to a vacuum, you are not removing any oil. You're just creating a negative pressure in the system that lets any moisture boil off and be removed before recharging.

 

[Matticus]

No, you are not sucking oil out. Each part of the system has a certain amount of oil in it. There are specs that say, for instance, if you replace the compressor, it has a certain amount of oil in it, and you have to add that much back into the system when you put the new compressor in it. The issue comes when you remove the refrigerant. If it's done slowly with an ac machine you lose very little, if any, oil. Most ac machines allow you to measure any that comes out, so you can put the same amount back in. If you just crack a line, who knows how much oil leaks out.

When you pump the system down to a vacuum, you are not removing any oil. You're just creating a negative pressure in the system that lets any moisture boil off and be removed before recharging.

Is refrigerant oily? Because I've always gotten a fair amount of an oily substance when I've pulled vacuum on a/c systems and always assumed it was some of that PAG oil

 

[William_ff]

Still have you measured the hi and low side yet? Ambient temperature is important and if the low side is perfect and the hi side is unexpected, that means something.

 

[Motorcity muscle]

Oil does mix with refrigerant and move thru the system. Small amount of oil will be lost with leaks and during recovery of refrigerant.

 

[1955moose]

I guess the consensus is put back in some pag oil. Theirs no dipstick, so you kinda have to punt on this one. If it was me evacuating freon, and replacing without any part replacement, I'd think about an ounce of oil would be a safe bet. Anyone want to comment?

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[fireguy926]

I have found that when I add freon, I can't just add based on the weight printed on the can. 2 different 12 oz cans of freon add differing amounts according to a scale. I started using an electronic scale to measure the true amount added. Works alot better! That being said, i started using an A/C shop for newer vehicles sin e they have much better equipment.
The A/C in my 12 Expy has always been mediocre for hot days when driving in alot of traffic.

 

[Matticus]

I have found that when I add freon, I can't just add based on the weight printed on the can. 2 different 12 oz cans of freon add differing amounts according to a scale. I started using an electronic scale to measure the true amount added. Works alot better! That being said, i started using an A/C shop for newer vehicles sin e they have much better equipment.
The A/C in my 12 Expy has always been mediocre for hot days when driving in alot of traffic.

I was thinking about trying the scale idea also. I have a little electronic scale I use for weighing food. It would probably work great for this. I'm hoping to get to this in the next few days. I'll update again with results. I'm sure everyone will be waiting on the edge of their seat to hear if my ac works better