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Old Jun 15, 2021 | 10:10 AM
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Default Air conditioning help.

I have a 1974 corvette with a R4 compressor. What is the r134a capacity for this car?

(Note): 4-28-2024:
1. car had a reman R4 on there (77-82) instead of an A6.
2. I put about a total of 36 OZ of r134a in the system.

Last edited by miked123; May 18, 2024 at 10:33 AM.
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Old Jun 16, 2021 | 12:03 PM
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Does this help?
https://www.techtownforum.com/knowle...%20refrigerant.
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Old Jun 16, 2021 | 04:28 PM
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Originally Posted by MelWff

thank you so much. My system requires 3lbs of R-12 and then conversion chart helped greatly!! Thank you!!
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Old Jun 16, 2021 | 04:40 PM
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you sure it isn't an a6?
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Old Jun 16, 2021 | 05:26 PM
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Originally Posted by derekderek
you sure it isn't an a6?
so an A6 compressor should of been installed for my car but for some reason an R4 was installed instead. I don’t know why an R4 was installed on there instead of an A6.

but the ac system works fine with the R4 so I’m not going to change it back. Eventually the system will be upgraded to vintage Air
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Old Jun 19, 2021 | 07:30 PM
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Also, the ac compressor I ordered needs PAG Oil, DO I use PAG 100 or 150 for the R4?
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Old Jun 19, 2021 | 10:54 PM
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ester. works with both 12 and 134. gets along better with the traces of mineral oil you didn't get out. and if it works fine, why order a new compressor? and if ordering a new compressor, why not a sanden style that is designed for 134? cheaper than an r4. same setup vintage wants 1500 for. https://www.ebay.com/itm/18415851344...BoCxikQAvD_BwE the brackets. the compressor. https://www.ebay.com/itm/30303415368...f764%7Ciid%3A1 then i got an 82 evaporator and accumulator which covers most of the VIR eliminator with a new style evap that doesn;t use the oil return. and i found a parallel flow condenser for 95 bucks. then you need the blue ford orifice the pressure cycling switch, and some adapter adapting to go from #6 to #8 on the liquid line.

Last edited by derekderek; Jun 19, 2021 at 11:03 PM.
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Old Jun 20, 2021 | 09:16 AM
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Originally Posted by derekderek
ester. works with both 12 and 134. gets along better with the traces of mineral oil you didn't get out. and if it works fine, why order a new compressor? and if ordering a new compressor, why not a sanden style that is designed for 134? cheaper than an r4. same setup vintage wants 1500 for. https://www.ebay.com/itm/184158513445?chn=ps&norover=1&mkevt=1&mk rid=711-117182-37290-0&mkcid=2&itemid=184158513445&targetid=1 263433205934&device=c&mktype=pla&googlel oc=9003795&poi=&campaignid=11614424777&m kgroupid=121942480053&rlsatarget=pla-1263433205934&abcId=9300456&merchantid=1 13583375&gclidCjwKCAjwq7aGBhADEiwA6uGZp2 abFo6nWcsH3ofgow6sFKuNqsx8M8aa45Kadwrtbl WcJP-ZRIvrrBoCxikQAvD_BwE the brackets. the compressor. https://www.ebay.com/itm/30303415368...f764%7Ciid%3A1 then i got an 82 evaporator and accumulator which covers most of the VIR eliminator with a new style evap that doesn;t use the oil return. and i found a parallel flow condenser for 95 bucks. then you need the blue ford orifice the pressure cycling switch, and some adapter adapting to go from #6 to #8 on the liquid line.
thanks for the reply! This is just a temporary fix for now until I can do the Vintage air set up. The old R4 came broken. So just need a new compressor and that’s all. Cost to fix it is going to be less than $200 to do it myself. I would like to do the Sanden conversion but the kits cost too much right now. Just graduated college and am now job hunting! Need to save (almost) every penny I get .

Again thank you for the reply about the oil, that really helps me a lot.
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Old Jun 20, 2021 | 10:33 AM
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The only difference in Pag 100 and Pag 150 is viscosity, I’m pretty sure the 100 is 10 weight and the 150 is 15 weight oil . Just like engine oil
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Old Jun 20, 2021 | 11:15 AM
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Originally Posted by Eric P
The only difference in Pag 100 and Pag 150 is viscosity, I’m pretty sure the 100 is 10 weight and the 150 is 15 weight oil . Just like engine oil

Yeah that makes sense.
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Old Jun 24, 2021 | 11:26 AM
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I got the ac working again!!! I got the compressor in, vacuumed the system and put r134a in it and it’s blowing cold now.

What I did:

1. Prepped R4 compressor from Rock Auto by putting in about 3 - 4 Ounces of PAG 150 oil and rotating clutch/letting it sit for a few days.
2. EVAC System of whatever is left.
3. Installed the R4 (worst three hours of my life due to a bent bracket/bent bolt) a hammer fixed that
4. Vacuumed system out for about 3 hours. Let it sit overnight and no leaks.
5. Next day recharged the system with manifold gauges, R134A and got it blowing cold.


Update (4-28-2024):
System is still working as it should. No leaking from compressor, no noises or anything.


2nd Update: [5-18-2024]:

1. I would highly recommend using PAG 150 oil in these R4's. I have been using the system for a while now and have had no noise OR leaks from the compressor, let alone anywhere else on the system. at this point.
2. ****I filled the system with three cans of r134a to get it blowing cold.

Last edited by miked123; May 18, 2024 at 10:32 AM.
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