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I just bought a wonderful, low-mileage Fifth Avenue, but on the last 50 miles of an 800-mile voyage home, the 35-year-old AC compressor seized. It blew ICE COLD but probably just sat too long and wasn't ready for a 12-hour drive. The car has a good battery, and I managed to get home without belts, thankfully.

Anyway, I had the compressor and belts replaced the following day, and the car has been garaged since it got home. Here's a link to the re-manufactured compressor which is now in the car.

According to this helpful website, it looks like I might need a third, or even fourth can of R12 in addition to the 2 my uncle gave me after he found out I bought this car. No problem. I can grab those off eBay.

The gentleman who installed the compressor advised me that my compressor came out of AutoZone with a few ounces of oil in it, and only needs a couple of ounces added. I am left with the question of what type of oil to use. That website is confusing, though, where it reads "If your vehicle was originally charged with R12 refrigerant, for example, the oil type specified, 'mineral', will not apply."

When I went to the local AutoZone in town, I told them I need compressor oil for an R12 system. He said they don't carry that. What am I meant to use?

Also, do I use a different amount of oil since I am having the system recharged with R12? As a side note, I am having a local mechanic do this since I don't trust myself with it. Should I ask them to ensure there are no leaks in the system?
 

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First of all you dont charge it with R12, period. There is a very good reason why its phased out.
You have 2 options:
-convert it and charge it with R134 and use the oil thats used with it.
- charge it will one of the "propane" substitutes like freeze12 or so and use almost what ever oil you what since these arent sensitive to differents types of oils unlike R12, R22, R 134 etc.
Oil selection for refridgerants are mainly based of what refridgerant dissolves what oil and "propane" substitutes arent picky at all, they work with almost any type of oil thats designed for refridgerant use.
 
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. . . According to this helpful website, it looks like I might need a third, or even fourth can of R12 in addition to the 2 my uncle gave me after he found out I bought this car. No problem. I can grab those off eBay. . . .
If you are going to purchase R12 on the Ebay platform, limited supply and high demand means you are going to pay excessively for this refrigerant. Now and in the future if you have leaks in the system. I would advise converting to R134a refrigerant.

. . . When I went to the local AutoZone in town, I told them I need compressor oil for an R12 system. He said they don't carry that. What am I meant to use? . . .
Follow this link and scroll down to POE / Ester oil. It is compatible with R12 or R134a refrigerant. When changing a vehicle air conditioning compressor you remove the failed compressor. You empty and measure the amount of oil in the refrigerant. That is the amount that should be in the replacement compressor.

Understanding the Differences Between A/C Compressor Oils – FJC Inc (at https://fjcinc.com/understanding-the-differences-between-a-c-compressor-oils/ )

The chart you referenced above (helpful website) indicates your system originally held 42 oz of R12 refrigerant and 7 oz mineral oil. Not all of the oil is retained in the compressor. Some gets dispersed to the receiver - drier, evaporator, condenser. So that is why one should measure the oil remaining in the failed compressor and then just add that same amount of new oil to the replacement compressor.

It appears that since the compressor switch has already been accomplished no one thought to measure the oil quantity in the failed compressor???

. . . Also, do I use a different amount of oil since I am having the system recharged with R12? As a side note, I am having a local mechanic do this since I don't trust myself with it. Should I ask them to ensure there are no leaks in the system? . . .
You would not want to add a full 7 oz of POE / Ester oil. Only the amount of oil in the failed compressor should be added with an equal amount of fresh oil to the system. As an alternative you could have the system completely flushed of old oil and then start anew with an addition of 7 oz of POE / Ester oil to the system. But you are asking for more air conditioning services and increasing your costs. But since the original compressor failed, flushing the system of any contamination is an advisable option.

Most definitely ask to have the system leak checked. R12 is limited and very expensive to be adding periodically to a system.
 

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Discussion Starter · #4 · (Edited)
Hi Allan, thank you for your detailed response.

I admit I did not understand the process of switching AC compressors. I have not worked on a Fifth Avenue since I was a teenager, and I have never changed a compressor myself. More to your point, the mobile mechanic who showed up at my friend's parking lot did not seem to know a great deal about that process either! I had to get the car on the road immediately, though, because where it broke down was still about 4 hours from home. He did his best, did not charge very much, and got me back on the road in the same day (albeit without air conditioning).

I will pass your advice along to the technician who finally works on my AC system when I get back to town, and pay the extra for him to perform the necessary steps to ensure my system does not leak. I think it is worth any extra to get the job done right. This is, afterall, my only car.

Just to be clear, if in my stubbornness I decide to move forward with putting R12 in my system, I should use mineral oil, right? Seems you advise POE/Ester oil based on your understandable desire to see me convert my R12 system to R134a.

Can a simple mechanic be trusted with this task?

Your wisdom is much appreciated. Thank you also for the informative link about compressor oil, and above all, thank you for taking the time to explain everything in such clear terms. You are a leader!

Honorable mention: AC for briefing me on my options.
 

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I’d worry less about taking it to a rod shop who probably never deals with A/C, instead finding a shop known for their A/C experience. Whether you choose to stick with R12 or convert, there will likely be more repairs needed to the system. Hoses, seals, etc. are all possible leak points among others.
 
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Since you don't know if the new compressor comes with mineral oil, or PAG, or ester, I'd use ester oil for the conversion. Safest choice to prevent clogs. PAG and mineral oil together will form a clog that is fatal to the system.
 
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. . . Just to be clear, if in my stubbornness I decide to move forward with putting R12 in my system, I should use mineral oil, right? Seems you advise POE/Ester oil based on your understandable desire to see me convert my R12 system to R134a. . . . .
You can still run your vehicle air conditioning system with R12 refrigerant if you do NOT mind the high cost of adding refrigerant. Now if you get the system sealed and it does not leak then the cost of the refrigerant is not as much an issue.

Starting with 1995 model vehicles sold in the United States with air conditioning systems, R12 was banned from usage. R134a was the refrigerant of choice. It takes a completely different lubricating, compressor oil. So where are you going to find this mineral based refrigerant oil used 25+ years ago with R12 refrigerant? With no demand why would a petrochemical facility manufacture it? So if you stay with R12 the POE / Ester oil is a good, price effective alternative. Using POE / Ester oil with R12 refrigerant will NOT degrade cooling performance. My strong suggestion for converting to R134a was to ease the pains in finding commodities (refrigerant and oil) not manufactured or used widely today.

I am very surprised by the number of advertisements on Ebay for R12 refrigerant. According to EPA regulations vendors should require purchasers to have a section 609 mobile air conditioning license. It seems vendors are selling with disregard to EPA regulations. One day the EPA may do a serious enforcement of the law and start imposing hefty fines on retailers and maybe even purchasers without the proper credentials??? So beware!
 

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I would think that it would be amazing for a 35 year-old vehicle to still have the R-12 charge still intact. Any A/C service since the late '90's would probably have been a conversion to R-134a, unknowns, mixtures, etc.
At the dealer when an older vehicle came in for A/C service, we had no idea what refrigerant or oil would be in it. There have been reports of propane and butane gases used as refrigerant (with subsequent service personnel injuries).

If it leaked with R-12, it will leak much worse with R-134a due to the smaller molecule. A/C hose and seal material has to be changed to withstand the new oil and refrigerant. Mixing incompatible oils and refrigerants can destroy a system.

Aftermarket A/C stop-leaks used in A/C systems did damage our shop equipment to the tune of several thousand dollars at the peak of summer A/C work. The customer either didn't know or disclose to us, what had been added in a previous service. Stop-leaks are a Hail-Mary repair.
After that, we were required to sample what was in the system before service. We declined any questionable indicated refrigerant compositions that might contaminate our shop A/C tools.

https://www.macsw.org/WEB/images/Macs_Docs/2019TETS/eaton.pdf
Air-conditioning dos and don’ts: Refrigerants and the law | Hagerty Media (at https://www.hagerty.com/media/maintenance-and-tech/air-conditioning-dos-and-donts-refrigerants-and-the-law/ )
 
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I've not had good results from 134 in older vehicles. HC-12 (propane mix) has worked well for me.
HC-12 has a higher flash point than 134, so I'm not concerned about flammability. Barbecue grade propane will cool very well, but there's a fireball waiting to happen. Whatever you put in, label the system clearly so that future service will be informed of what's in there.

On newer vehicles that came with 134 I've not had good results with HC-12 and use 134 in them.

You really need to find out what oil the new compressor shipped with. AZ won't know, contact the supplier.
 

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I would think that it would be amazing for a 35 year-old vehicle to still have the R-12 charge still intact. Any A/C service since the late '90's would probably have been a conversion to R-134a, unknowns, mixtures, etc.
At the dealer when an older vehicle came in for A/C service, we had no idea what refrigerant or oil would be in it. There have been reports of propane and butane gases used as refrigerant (with subsequent service personnel injuries).

If it leaked with R-12, it will leak much worse with R-134a due to the smaller molecule. A/C hose and seal material has to be changed to withstand the new oil and refrigerant. Mixing incompatible oils and refrigerants can destroy a system.

Aftermarket A/C stop-leaks used in A/C systems did damage our shop equipment to the tune of several thousand dollars at the peak of summer A/C work. The customer either didn't know or disclose to us, what had been added in a previous service. Stop-leaks are a Hail-Mary repair.
After that, we were required to sample what was in the system before service. We declined any questionable indicated refrigerant compositions that might contaminate our shop A/C tools.

https://www.macsw.org/WEB/images/Macs_Docs/2019TETS/eaton.pdf
Air-conditioning dos and don’ts: Refrigerants and the law | Hagerty Media (at https://www.hagerty.com/media/maintenance-and-tech/air-conditioning-dos-and-donts-refrigerants-and-the-law/ )
It IS rare to have a good R-12 system at this point. But my 92 Dakota had factory R-12 charge in it in 2015, at 24 years old, and it cooled great, no issues. The heater core failed, however, requiring me to open the system. I had the R-12 recovered and opted to switch to R-134a for convenience. It's run fine since. It cools just as well as the R-12 did. But it is an extended cab, somewhat smaller than many cars, and the cap on the bed blocks the sun from the rear window, so the cooling load is not great.
In 2018, the compressor clutch cracked and started making noise and a little smoke, but I was able to procure a new clutch off a reman compressor and change it without opening the system.
 
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