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I had a shop replace replace pretty much everything in the A/C system except the evaporator and condenser in 2008. It's a '95 so it uses R134A. It got weaker the past few years and recently it started short cycling because the pressure was too low. I bought an 18 oz. recharge kit (no dye, no oil) and it surprised me when it took all 18 oz. to get the pressure back up to 40 p.s.i. at 75 degrees (with the compressor running). My Hayne's manual says it uses 28 oz., so it lost 64% of its refrigerant. Did it lose 64% of its oil? How much of what oil do I need to add to protect the compressor? The receipt says they used $28 worth of FrigiQuiet in 2008 (not the amount). I can get 3 oz. of PAG 100 at Walmart for about $7. Yes, I know it has a leak. I will know how bad the leak is by how long it takes to start short cycling again. I did try searching this forum, but I did not find answers and eventually I was asked to donate to the Red Cross or it wouldn't let me search anymore.
 

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the system uses pag 150 oil. also you should add the leak detector . possible the seals are leaking or the pressure fitting ports [valves] including the low pressure switch valve port.

newer vehicles much newer not these antiques use the pag 46/100 oil.

low levels of oil will cause leaks. the seals require a refrigerant oil placed on them to provide a good seal . disturbing the pressure ports 20 plus years old these will leak. using a UV black light with the dye this will find leak fast. on these vehicles loosing some refrigerant is common of this vintage new vehicles have a more secure system on leaks .

adding refrigerant to the system the idle must be 1100 rpm the fan on max all the doors open and the air temp 80-85 deg f .. continue to add until both fans come on . now you should be good. as soon as the sec fan comes on no more refrigerant !!!!!!!!!

remove the can with the system running not OFF ..3OZ of pag 150 oil will not damage anything . best have a little more than less .. it the system has more oil than the spec which I believe is 8-9 OZ.. the only thing that happens is a reduced efficiency an amount you will not notice . over time though this will gradually reduce as it leaks out .

loss of 6OZ -12OZ over 2 years is about normal on these .
 

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Thanks for the information, j cat. I added 3 oz. of PAG 150 and the compressor got noticeably quieter. I do regret that it is going to leak a little of a powerful greenhouse gas, but a proper repair is very expensive and it may not be necessary for years. Time will tell.
 

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Oil type is dictated by the replacement compressor used, or what the shop utilized when they serviced the car, not necessarily year of car/what it originally used for oil.\

Using the wrong oil can cause catastrophic compressor failure under certain circumstances.
I would have tried to find out what was in there before adding any oil.

You may be fine...time will tell.
 

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Thanks for the information, j cat. I added 3 oz. of PAG 150 and the compressor got noticeably quieter. I do regret that it is going to leak a little of a powerful greenhouse gas, but a proper repair is very expensive and it may not be necessary for years. Time will tell.
R134 is NOT a ozone killer it is a safe refrigerant. R12 has CFC'S that is the bad stuff....

the oil that these used is PAG 150 oil..... now when a new compressor is used you dump out that compressor oil and add the oil your vehicle requires . then you add a total of 8-9 OZ... I add the 9 OZ.. because I know over time it will weep out and a little more is better than running low and then seals and compressor have issues.

the compressor making sounds usually means low oil/refrigerant .. since you add oil and it is quiet then the oil was too low.

I also recommend a long vacuum pumping on the system when replacing the compressor this is because of the system holding water / air so it does take time to boil off this contamination .

I did this work on big vehicles .. vacuuming the system for an hour or so will do it on these small systems. not 15 MIN ..................

I guess it will be now 4 years since I replaced my compressor . the compressor seals broke down and all the oil leaked out . so far I am cool .. the only problem I had was the NEW filter dryer O ring was defective ...on the low pressure switch .. as I always say , new does not mean its good.............
 

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??Weight vs Volume??

Guys I was reading an article the other day on Ounces and how it is measured and it made me wonder about our AC Systems/Specs. My question is, the standard specs of 28oz(R-134)/8oz(PAG150) for our cars...should we take this in terms of weight or volume because there is a difference. What do you guys think?

Thanks!
 

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Guys I was reading an article the other day on Ounces and how it is measured and it made me wonder about our AC Systems/Specs. My question is, the standard specs of 28oz(R-134)/8oz(PAG150) for our cars...should we take this in terms of weight or volume because there is a difference. What do you guys think?

Thanks!
liquid volume on the oil .....weight on the refrigerant . on larger systems I worked , one used 30 LBS of weight R22 . used a scale to charge but in the end the pressures and the sight glass were used to see if things were working properly..

in the old days vehicles had a sight glasss on the filter dryer .. you could look at that and if bubbles then you know it is low or some other problem..
 

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Update on added refrigerant.

The A/C is still working. It's been about 2.7 summers now and the summers are long here along the Gulf Coast. I knew it had a leak that was not obvious and it turned out that the leak is small so my gamble paid off, I think. BTW, R-134 is a potent greenhouse gas so it will be phased out soon on new cars. https://www.epa.gov/mvac/refrigerant-transition-environmental-impacts
 

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I appreciate the link. VERY interesting developments, and equally interesting seeing the new cars that have already moved from the current refrigerant.
 

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More turmoil. I guess we should stock up on the 134a. I wish I had done that when R-12 was 75 to 99 cents a can. My little pick up, 91 B2600, would be a lot cooler today. I'm about to change it over to 134 now. Geesh! But there is some good info here. Thanks.

Mark: Snowman-33
 

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I just installed the 4 Seasons 88955 upgraded compressor on my 95 Caprice wagon. It calls for PAG 46 oil. I flushed all the lines and the condenser and evaporator and added the PAG 46. The car goes to the shop tomorrow for leak test, evacuate and charge. New dryer and orifice tube installed.
The upgrade is the use of dowel pins to locate the compressor housings.
So oil use depends on which parts are installed and may require flushing the old oil out. I used the 4 Seasons flush solvent.

Ken
 
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