Which weight (PAG) refrigerant oil for GMT400 R12 to R134a

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Hi All, I have a 1991 Chevrolet K1500 which I want to convert from R-12 to R-134a as the A/C blows warm and the R12 is hard to service especially if dye needs to be added to source a leak which this truck may or may not have. I was told by a mechanic to convert it over to the newer freon as the dye he will add is only compatible with the R-134a. I have advance auto parts store credit so I'll use them for the parts. I'll be buying this conversion kit: https://shop.advanceautoparts.com/p/auto...rm=r12+to+r134a I'll also need the 8oz. Refrigerant oil. Looking at the Advance auto parts site, they sell them with ester (no pag indicated on the bottle? - medium viscosity), Pag 46 (low viscosity), Pag 100 (medium viscosity) and pag 150 (highviscosity). https://shop.advanceautoparts.com/web/Pa...doExactFit=true Which would I need? Anything else other than freon is required for this conversion? Thanks for the help!
 
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I used Ester oil when I converted my Accord. It's supposed to play nice with any residual mineral oil left in the system. I did the conversion seven years ago and it's still working great.
 
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Originally Posted By: Char Baby
Doesn't all standard/most basic R134a already have PAG oil in it?
No. R134a never has any PAG oil in it. How could it when different vehicles use different viscosities of PAG oil? Most of the cheesy DIY recharge kits often have stop-leak and other gimmicky additives that supposedly make it cool better, but plain old R134a doesn't have any oil or other additives in it.
 

VK56VD

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Guys, I'm asking about the refrigerant oil not the freon. Looks like if you're converting from R12 to R134a, NOT to use refrigerant oil with PAG as the remaining oil won't be compatible leading to problems.
 
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Originally Posted By: Spartuss
Guys, I'm asking about the refrigerant oil not the freon. Looks like if you're converting from R12 to R134a, NOT to use refrigerant oil with PAG as the remaining oil won't be compatible leading to problems.
Yes, which is why I said in my first post to use Ester oil.
 

VK56VD

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Originally Posted By: exranger06
I used Ester oil when I converted my Accord. It's supposed to play nice with any residual mineral oil left in the system. I did the conversion seven years ago and it's still working great.
Have you noticed a degraded performance after the conversion? I've read online that our compressors are made for R12 and aren't as effective after the conversion to R134a. Did you replace the drier or left everything as is? Input?
 

VK56VD

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Originally Posted By: exranger06
Originally Posted By: Spartuss
Guys, I'm asking about the refrigerant oil not the freon. Looks like if you're converting from R12 to R134a, NOT to use refrigerant oil with PAG as the remaining oil won't be compatible leading to problems.
Yes, which is why I said in my first post to use Ester oil.
Thank you!
 
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Originally Posted By: Spartuss
Originally Posted By: exranger06
I used Ester oil when I converted my Accord. It's supposed to play nice with any residual mineral oil left in the system. I did the conversion seven years ago and it's still working great.
Have you noticed a degraded performance after the conversion? I've read online that our compressors are made for R12 and aren't as effective after the conversion to R134a. Did you replace the drier or left everything as is? Input?
I get 41 degree vent temps on an 85 degree day, so I'm very happy with the performance. The only things I did during the conversion is remove the compressor, drain the oil out, add a few ounces of Ester oil and reinstalled the compressor. I replaced the drier (and add a few more ounces of oil to it), replaced all of the easy-to-access O-rings and didn't bother changing the difficult to access ones, installed the adaptor fittings, and vacuumed it down, checked for leaks, and charged it up.
 
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Originally Posted By: exranger06
replaced all of the easy-to-access O-rings and didn't bother changing the difficult to access ones,
I've did that too when replacing a compressor. So far so good.
 
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You use ester oil when retrofitting to r134a. Page oil is not in any way compatible with the mineral oil left in the system. Make sure to install an orifice with a smaller hole. The r12 orifice is too big for r134a to work well. The orifice is behind the passenger side turn signal light..
 
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GM used to specify ISO 150 viscosity PAG oil, now their "universal" spec in Harrison/Delphi compressors is ISO 100. I would use POE(ester) oil. PAG oil, even the fancy Idemitsu stuff used by the Japanese and Koreans is very hygroscopic and doesn't mix well with mineral oil. I would try to get as much of the old mineral oil out and add in a like amount. Too much oil is just as bad as too little, while some will end up in the accumulator and condenser on a older GM system, it's always a good idea to keep the oil capacity close to OEM specs. If you installed a new system(compressor, lines, accumulator, heat exchanger) you can go ahead and use PAG and the stated oil capacity listed on the accumulator or compressor.
 
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If you're converting an old R12 car to R134a, use ester. It is compatible with old R12 mineral oil residue, while PAG is not. The last time I used a retrofit kit, it came with a couple cans R134a, a small can of ester, and the adapters
 
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