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how do I figure out how much oil to add to ac system on recharge?

Dono

04 GT
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04 Mustang GT
My particular scenario is that I have evacuated my ac a few times, and left components in the open air for quite a while in between motor removals (Different painful story).

I have lost oil each evacuation, and understand its best to change it anyway due to moisture in the oil..

Here's what I have:
1. dual gauges for high and low side.
2. evac pump.
3. 8 oz of synthetic oil in a bottle
4. a new ac dryer
5. a new variable orifice tube
6. red-tec in cans (I'm guessing similar to a mix of propane and butane)
7. ac compressor laying on the floor with all kinds of other motor bits, and an empty engine bay

The decal on my rad support says not more than 9oz of oil.
I thought I could just drain the remainder of oil from my compressor and re-fill with 8 oz of my new oil. @ranger7ltr mentioned in another thread I hijacked that there will be very little oil in the compressor.

So, my question becomes...What is the correct prep work and parts to change/oil to fill before evacuating and re-filling the system once the motor goes back in. How could I possibly know how much oil to add? I only need to get in to the oil part and components I should change as I know how to pull a vacuum and recharge the system.

ps...Don't hate on me for red-tek. Its an environmentally friendlier refrigerant and actually should work extremely well if the correct prep work is done. No propane haters as the gas in my gas tank and fuel lines is at least as volatile. Lets keep this on track.
 



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:dunno:Since you don't know how much oil is in there. This is what I would do evac the system, then put in about 4oz oil doubt you lost more than that (but don't know) and the rest r134a. It should say under the hood how many ounces you need all together. I'd rather have a little more oil than not enough.That being said I would use my best guess for oil. JMHO
 






Thanks for the reply Pete. I kinda thought there would be some sophisticated wild arsed guessing involved.
The new orifice tube instructions say to replace the accumulator also (which I have) and add 2 oz of oil. So, I think I will drain my compressor in to a measuring cup also, and see how much comes out. Then at least I know to replace at least how much comes out of the compressor + 2 ounces.

Here's a couple of pics for anyone that is curious (Obviously those with experience in auto ac won't care). One is the orifice tube location in a 5.0 explorer, and the other is the comparison of the old orifice tube to a variable one. From the pic of the crud in the old orifice tube, I'm glad I'm replacing it.

orifice tube location.jpg


Orifice tube comparison.jpg
 






I replaced my orifice tube a couple of years ago and it looked close to your's,
You'll see a big difference in cooling. Mine blows real cold now, i'm sure your's will also.
 






From the workshop manual about adding oil:
1. NOTE: Service A/C compressors (19703) are shipped without compressor oil.

Rotate the A/C compressor shaft six to eight revolutions while collecting oil in a clean measuring device.
  • If the amount of oil drained from the old A/C compressor is between 85-142 ml (3-5 ounces), pour the same amount plus 30 ml (1 ounce) of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B into the new A/C compressor.
  • If the amount of oil that was removed from the old A/C compressor is greater than 142 ml (5 ounces), pour the same amount drained of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B into the new A/C compressor.
  • If the amount of oil that was removed from the old A/C compressor is less than 85 ml (3 ounces), pour 85 ml (3 ounces) of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B into the new A/C compressor.

2. For the suction accumulator/drier (19C836), drill two 1/2 inch holes in the suction accumulator/drier cylinder and drain the oil into a calibrated container.
  • Add a quantity of new oil to match that drained from the old suction accumulator/drier plus 60 ml (2 ounces) of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B.

3. For the A/C evaporator core (19860), add 89 ml (3 ounces) of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B to the suction accumulator/drier inlet tube.

4. For the A/C condenser core (19712), add 30 ml (1 ounce) of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B to the A/C condenser core or the suction accumulator/drier inlet tube.

5. Add 60 ml (2 ounces) of clean PAG Refrigerant Compressor Oil (R-134a Systems) F7AZ-19589-DA (Motorcraft YN-12-C) or equivalent meeting Ford specification WSH-M1C231-B to the suction accumulator/drier inlet tube when carrying out each of the following repairs:
  • installation of a new A/C evaporator core orifice (19D990)
  • installation of a new A/C compressor pressure relief valve (19D644)
  • installation of a new refrigerant line
  • repair of an O-ring seal leak
  • repair of a charge port leak
6. Installation of new components that do not require discharge of refrigerant and resulting oil loss, such as the A/C cycling switch (19E561) and the A/C pressure transducer, do not require additional oil.
 






lol. looking at that list of how much oil to replace, I'm betting I'll end up using pretty close to 6 oz of oil. Considering the label says 'Not more than 9 oz' Id say that's quite a bit of oil. I'll be interested in how much oil is left in the compressor.

Great news on the orifice tube Pete, Thanks for the oil info Collin. The last couple of motor changes I wasn't nice about letting the red-tec evacuate. It was more of a pull the line on the drivers side of the condenser and let everything spew kinda deal. Not pretty, but I am getting pretty tired of pulling this motor over and over again. Not a great excuse, but I might as well be real about what goes on.

You guys have been a great help. Thank you.
 






My particular scenario is that I have evacuated my ac a few times, and left components in the open air for quite a while in between motor removals (Different painful story).

I have lost oil each evacuation, and understand its best to change it anyway due to moisture in the oil..

Here's what I have:
1. dual gauges for high and low side.
2. evac pump.
3. 8 oz of synthetic oil in a bottle
4. a new ac dryer
5. a new variable orifice tube
6. red-tec in cans (I'm guessing similar to a mix of propane and butane)
7. ac compressor laying on the floor with all kinds of other motor bits, and an empty engine bay

The decal on my rad support says not more than 9oz of oil.
I thought I could just drain the remainder of oil from my compressor and re-fill with 8 oz of my new oil. @ranger7ltr mentioned in another thread I hijacked that there will be very little oil in the compressor.

So, my question becomes...What is the correct prep work and parts to change/oil to fill before evacuating and re-filling the system once the motor goes back in. How could I possibly know how much oil to add? I only need to get in to the oil part and components I should change as I know how to pull a vacuum and recharge the system.

ps...Don't hate on me for red-tek. Its an environmentally friendlier refrigerant and actually should work extremely well if the correct prep work is done. No propane haters as the gas in my gas tank and fuel lines is at least as volatile. Lets keep this on track.

This is what I would do...
1. Change the oil in your vacuum pump before you use it...
2. Verify the accumulator is still sealed up tight...
3. Blow out the condenser with compressed air so there is no oil left inside the condenser.
4. Replace all the o-rings in the system even the ones that you didn't open up...Use the light green o-rings when putting everything back together...Lube the o-rings with oil on the orifice tube and Nylog on the connections...
5. Add 4 oz synthetic oil to the condenser...Add 4 oz. to the accumulator...Then seal the system and connect your gauges...
6. Connect your vacuum pump to the gauge set and turn it on...
7. Open the low pressure side and watch the low pressure gauge drop into vacuum...After a few minutes close the low side valve and see if the vacuum level stays put... If it does turn your pump back on, open the low side valve again and let the vacuum pump suction the system down for 30 to 60 minutes...If the vacuum level starts to go up re-check all connections and o-rings because you got a leak somewhere...
8. After the system is vacuumed down, close the low side valve again and watch the gauge...Yep check for leakage...If all stays the same, remove the vacuum pump and then get ready to charge the system with your choice of refrigerant...

Not knowing how red-tek works I would think to get the same cooling as R-134a you would need to load the system to a higher level since the molecules of red-tek are probably smaller than R-134a and won't absorb heat or change state as readily as R-134a... But I have seen propane and other refrigerants work in the automotive world so I would guess it is not impossible to get it working in a well prepped system...

The amount of oil in the Ford compressor is minimal but oil exposed to the atmosphere will absorb moisture and turn acidic even if you vacuum all the moisture out of it...Blowing out the condenser and replacing the accumulator is the best move you can make and replacing the oil in both minimizes the work the vacuum pump needs to do and insures the closed system has no or as little air in it as possible...

But let's talk about the old orifice tube...If this picture is your old orifice tube you have some major issues going on here...You have the beginnings of Ford black death...The particles on the orifice tube screen are teflon and aluminum from the insides of the compressor...Also if the oil coming out of the system is black or creamy dark grey I would consider doing a system flush if not replace the condenser and compressor...That look shows your a/c system has been hot as hell and has started to consume itself...As your system runs and the high side pressures increase, the wear will gradually eat away at the worn compressor and clog up the orifice tube along the way...Most of the particulate stops at the orifice tube and just raises system pressures but the dirty oil will flow past the tube and either work its way through back to the compressor or stop before it gets to the compressor and starve it for lubrication...
 






Did some research on RedTek....Are you using Redtek 12a? If you are the conversion for R-134a is here....RED TEK - Technical Information

Looks like you need to use LESS RedTek than R-134a to have the similar cooling...I was wrong assuming that RedTek molecules are smaller than R-134a and you needed to charge to a higher level... That would work your compressor less and should cause less wear and decent cooling with the system being clean and dry....

I would like to know what you see pressure wise and temperature wise when you are done...
 






I use red tek 12a in my 92 but it’s still r12. Any reason to use red tek over 134 because I pay a lot more for it?
 






Considering the label says 'Not more than 9 oz' Id say that's quite a bit of oil. I'll be interested in how much oil is left in the compressor.

Sounds like a plan.

Remember, more oil is better but more oil displaces replaces refrigerant volume and could reduce cooling power.
 






Due to licensing here in Canada, red-tek is less expensive than 134a and readily available.

Thanks for diagnosing that black crud in my orifice tube. Now's the time for me to be replacing stuff as its really easy to get at. The compressor is a bit more cash than I'd like, but I'll add it to my list as I get closer to the motor being finished. As my junk gets older, even the regular maintenance adds up, not to mention the go fast stuff.
 






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