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I'm replacing my AC condenser (and drier) in my 95 and I'm trying to figure out the capacities and volume of oil and refrigerant to put in. The system has been fully vacuum evacuated.

The capacity charts from the third party companies seem like a ton of both - almost seems like double what it ought to be. And they also don't seem to line up with what I'm seeing in the service manual.

 

Of course it's hard to know if the oil to refrigerant ratio was right when the system was emptied... So how does one ensure the right amount of oil is in the system? And then what should be the volumes or pressures I should be aiming for?

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Posted (edited)

Here is what the FSM says:

image.png.e49f5706a30ea0ff31a023299609c995.png

 

That should give you a good basis to start. The refrigerant should be on a sticker under the hood. Mine was near the brake booster.

 

FSM link: https://www.nicoclub.com/service-manual?fsm=Pathfinder/1995/ha.pdf

 

I just went through this on my Xterra and added the amounts it said to in there. Everything is working great so far. The only way to know if the system is perfectly adjusted would be to remove the compressor, drain it, flush out all the lines, etc. I didn't feel like doing that. I erred on the side of a little too much oil. It still cools to 38F though.

Edited by adamzan
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Yeah there's that section of the FSM that talks about running the compressor to bleed off oil if you have too much (can't remember the exact wording at the moment). I just didn't quite understand that one.

 

Do you happen to recall the psi you ended up at? Or did you just add the quantities blind based on volume?

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The measurements are done by weight with the AC. You can't really go by psi because temperature has a huge effect on the pressures. 

 

If you have only replaced the condenser and dryer, and did not flush out the system, I generally add 1-2 oz of oil to the system. I then pull a vacuum for a few minutes  on the system to ensure no leaks and remove as much air and moisture as possible. Then I charge with the amount of refrigerant that the label or manual if the label is missing calls for. Then with the AC running I will watch the pressures to see how well it is working, but that is watching the differential between the high and low sides. As a general rule with most 134a systems, at 80°f environment, low side is usually 30-45 psi with high side about 180-260 psi.  

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Posted (edited)
On 5/21/2020 at 10:41 PM, Volox said:

Yeah there's that section of the FSM that talks about running the compressor to bleed off oil if you have too much (can't remember the exact wording at the moment). I just didn't quite understand that one.

 

Do you happen to recall the psi you ended up at? Or did you just add the quantities blind based on volume?

Like Mr. Reverse said, it goes by weight. I used a kitchen scale and measured the whole apparatus sitting on it before hand, then just noted how much went in. You can just use a syringe and put the oil in the lines. That's what I did, I wasn't buying a 100 dollar oil injector lol. 

 

And Rustflames just posted the sticker I was talking about! I'm not close to my truck right now and I doubt my Xterra is exactly the same.

 

As for the oil I couldn't find PAG oil near me, at least no one would sell it to me, but I did find ester oil with dye, which is supposed to be compatible. I did that work in 2016 and it hasn't blown up yet! And it is colder than most of my friend's new cars.

Edited by adamzan
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