How to get right amount of oil in AC system?

cb474

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The R134a currently in the system needs to be removed and saved before you open up the system. Even though R134a does does not effect the ozone layer, it's still a greenhouse gas and a cause of global warming.

You need to pull a vacuum and make sure the system can hold it for an hour.

Then fill the system by weight.
Right. I'm already planning to take it to a shop to evacuate the system and then do the recharge, after I put the new parts in.
 
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Thanks to everyone for the thoughts on this.



Thanks for the suggestion. Can I add all of that together directly to the compressor (because it will get circulated through the system)? Or should I add 1 oz directly to the drier through one of the ports where the lines connect?
Put the oil wherever you can. It circulates.
 
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The Japanese OEMs have a “oil recovery” procedure in their FSMs - run the car on max defrost/AC, max fan, recirc for 10-15 minutes IIRC.

Else, find the car’s service documentation and add in the specified oil for that part being replaced or major leak.
 

cb474

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Thanks. That's interesting. My system isn't really functional now to do that. But that's good information.
 
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Just another thought that may or may not help. If you don't have a vacuum pump, you can use a vacuum line from the intake manifold of the engine to pull a modest vacuum on the system. It won't remove all the air, but it will help considerably. And given some creative thinking, you might be able to figure out a way to purge what remains of the air using this same method.
 

wtd

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I went to the same forum and read all I could before rebuilding/converting the system in the Lumina in 2011 (compressor failure = Black Death). The car is falling apart and ready the scrap yard but the AC still runs frigid.
I first went to that forum to learn how to convert a 1992 Cavalier from R12 to R134a and how to repair AC systems in general. I learned enough from the forum and a couple of books I bought to do the conversion and had a working system for years until the compressor leaked all of the refrigerant out. I still have the car and may repair it again at some point but it's mainly just an extra car so it doesn't get driven much anymore.
 

cb474

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Just another thought that may or may not help. If you don't have a vacuum pump, you can use a vacuum line from the intake manifold of the engine to pull a modest vacuum on the system. It won't remove all the air, but it will help considerably. And given some creative thinking, you might be able to figure out a way to purge what remains of the air using this same method.
That's a clever idea. I'm planning, though, to take it to an auto ac shop to have them evacuate the system and then recharge it after I replace the parts. It's not too expensive and seems worth having done by someone with the right equipment. I could borrow a pump and the manifold gauges for free from O'Reilly's and recharge the system myself. But I feel like maybe it's better to have that part done professionally.
 

cb474

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Put the oil wherever you can. It circulates.
This is unrelated to my original question, but is it worth having the condenser (or anything else) flushed, while I have my car at the auto ac specialist to get the ac system evacuated? I think they said flushing the system costs $80, which I'd rather not pay given my money situation (although perhaps for just the condenser it would be cheaper, I guess). And I've read that modern condensers have such narrow passages that they can't really be effectively flushed. But maybe that's not true? As mentioned in the OP, I'm replacing the compressor, drier, and high pressure hose so those don't need to be flushed. My undrestanding is that you can't flush the expansion valve, so I don't know if that really leaves anything else other than the condenser. And, again, since my compressor did not seize and technically still works, perhaps there just is no need for flushing.
 

wtd

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This is unrelated to my original question, but is it worth having the condenser (or anything else) flushed, while I have my car at the auto ac specialist to get the ac system evacuated? I think they said flushing the system costs $80, which I'd rather not pay given my money situation (although perhaps for just the condenser it would be cheaper, I guess). And I've read that modern condensers have such narrow passages that they can't really be effectively flushed. But maybe that's not true? As mentioned in the OP, I'm replacing the compressor, drier, and high pressure hose so those don't need to be flushed. My undrestanding is that you can't flush the expansion valve, so I don't know if that really leaves anything else other than the condenser. And, again, since my compressor did not seize and technically still works, perhaps there just is no need for flushing.
Most modern condensers cannot be flushed. I don't think you need to get the system flushed unless you find evidence of debris in the system. I've not replaced condensers in vehicles that just had leaks and no compressor failure and have been fine.

I just helped fix the AC in my fiancé's dad's 2007 Ford F350 that wasn't cooling well. No obvious signs off leaks and the compressor was totally quiet when running. He had the system evacuated and asked me to recharge to factory specs which I did. Still no change in cooling.

He decided he wanted to replace the compressor and accumulator anyway since the truck had 230,000 miles on what we believe was the original compressor. When we removed the orifice tube, it was totally blocked with debris and what looked like sawdust particles. I was very surprised that the compressor wasn't locked up or making a ton of noise after seeing the condition of the OT.

He ended up buying a new condenser as well and flushing the lines and evaporator. I vacuumed they system and then charged to factory specs and it now works like it should.
 

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@wtd Thanks. I was just looking to see if my Mazda has an orifice tube, but I don't see it anywhere on the diagrams in the Mazda service manual and it's not a part that Rockauto or others list as available for my car. Does that seem plausible? If so, I may not have a way to check how dirty or not the system is.
 

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@wtd Thanks. I was just looking to see if my Mazda has an orifice tube, but I don't see it anywhere on the diagrams in the Mazda service manual and it's not a part that Rockauto or others list as available for my car. Does that seem plausible? If so, I may not have a way to check how dirty or not the system is.
Not all vehicles use an orifice tube so it's very possible that yours does not have one.
 

cb474

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The amount that went out the hose is very minimal. I would drain the old compressor and let me know how much you got out. Are you changing the reciever drier too? Is it a bag or a metal cyl?


Edit: I looked at the reciever online. I would add 1 oz of oil for that. I would add 1/2 oz for the leaking line. Then measure what I got out of the compressor+ another 1/2 oz.
@cb474 The entire system takes 5 ounces.
So I had the system evacuated. The technician at the AC shop said the machine pulled 1.75 oz of oil out with the evacuation. He also said that they always make sure there are 4 to 5 oz directly in the compressor, before they install it.

I explained that the spec from the Mazda service manual for the whole system is 5 oz (although I still find the wording confusing, "A/C compressor oil sealed volume (approx. quantity)" = 5.07 oz). The technician really didn't believe that was right, but basically said, do whatever you want.

He also said you never really can drain all the oil well from the old compressor to know how much was in there, so he was dubious about that method. (That being said there's shipping oil in the new compressor, so I do have to drain that all somehow.) And the technician pointed out my old compressor was leaking (in addition to the high pressure hose), which I thought might be the case when I was tring to repair the clutch, so he thought it's anyone's guess how much has leaked and what's really in there.

So I'm wondering if I should just put 5 oz in the new compressor and call it a day.
 
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So I had the system evacuated. The technician at the AC shop said the machine pulled 1.75 oz of oil out with the evacuation. He also said that they always make sure there are 4 to 5 oz directly in the compressor, before they install it.

I explained that the spec from the Mazda service manual for the whole system is 5 oz (although I still find the wording confusing, "A/C compressor oil sealed volume (approx. quantity)" = 5.07 oz). The technician really didn't believe that was right, but basically said, do whatever you want.

He also said you never really can drain all the oil well from the old compressor to know how much was in there, so he was dubious about that method. (That being said there's shipping oil in the new compressor, so I do have to drain that all somehow.) And the technician pointed out my old compressor was leaking (in addition to the high pressure hose), which I thought might be the case when I was tring to repair the clutch, so he thought it's anyone's guess how much has leaked and what's really in there.

So I'm wondering if I should just put 5 oz in the new compressor and call it a day.
I would wait for @Chris142 to see this post, I haven't replaced a compressor in a while. I agree with him, that you should drain what's in the old compressor and then go from there. Furthermore, your vehicle does not have an orfice tube, it uses a TVX.
 

wtd

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If you are putting 5 oz of oil in the system. I would put about 3 in the compressor and 2 in the drier. Turn the compressor about 12 times to distribute the oil around in the compressor.
 

cb474

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I would wait for @Chris142 to see this post, I haven't replaced a compressor in a while. I agree with him, that you should drain what's in the old compressor and then go from there. Furthermore, your vehicle does not have an orfice tube, it uses a TVX.
Thanks. Yeah, draining the old compressor is what the service manual says to do.
 

cb474

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If you are putting 5 oz of oil in the system. I would put about 3 in the compressor and 2 in the drier. Turn the compressor about 12 times to distribute the oil around in the compressor.
Both of the lines to the drier connect on the bottom. It seems like if I pour oil in there, it's going to drain back out when I install the drier. It would be hard, I'd think, to turn it rightside up with the ports down and connect both lines quickly enough not to have oil running out.
 
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Just another thought that may or may not help. If you don't have a vacuum pump, you can use a vacuum line from the intake manifold of the engine to pull a modest vacuum on the system. It won't remove all the air, but it will help considerably. And given some creative thinking, you might be able to figure out a way to purge what remains of the air using this same method.

Doesn't Autozone or Advance Auto have a vacuum pump in their loaner tools?
 

cb474

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This is kind of a silly question, but I can't figure out if the compressor I'm installing has an oil drain plug or not. There is a big bolt or nut on the bottom of the compressor that looks like somthing that would be a drain plug. But it has a foil sticker on the top of it and if you push down you can feel that there's empty space underneath. So it seems it may be more like a nut on something and not like the typical simple drain plug bolt. Every other compressor that has a drain plug, that I can find an image of, just has a simple obvious bolt head.

Also, for what it's worth, in the Mazda service manual, the schematic showing oil being drained out of the compressor, shows it pouring out of the discharge and suction ports and does not mention a drain plug. But maybe that's just a generic image?

Here's an image of the style of compressor I'm installling. The nut/bolt with the foil sticker is in the lower left hand corner in this image. If you look closely you can make out the sticker on the top of the nut/bolt.

1661448525113.png
 
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Usually the compressors come with enough oil in them for the entire system.

I know this will be an unpopular opinion, but I've always just bolted them and pulled vacuum/charged, never had a problem. As said a couple extra ounces of oil won't really affect anything.
 
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