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Old 07-29-2018, 12:10 AM   #1
bautino95
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what should my a/c pressures be for r-12

I have an all stock 1971 402. The a/c blows cool but not cold. I have a few cans of r-12 laying around still .I did a search but can find what the high and low side pressure should be for a stock r-12 system. I have an old A/C book laying around and for GM with SVT it says low should be 28.5-31.5 and the high should be 210-260. does this sound right? Thanks
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Old 07-29-2018, 08:47 AM   #2
engineer_gregh
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Re: what should my a/c pressures be for r-12

Pressures are effected by ambient temperature, thats why you see a range in the numbers you've listed. I've gone through the A/C on my 71 big block truck, I converted to R134a. If I may make a suggestion, make sure someone hasn't put 134a in your truck previously before wasting the R12. FAA Benny is the A/C expert on the board.
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Old 07-29-2018, 11:23 AM   #3
Steeveedee
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Re: what should my a/c pressures be for r-12

The numbers you quoted are close enough. You have a sight glass on your receiver-dryer. You can look for bubbles when the system is running. Bubbles generally indicate gaseous refrigerant leaving the condenser, which means low refrigerant level. It can also mean air in the system, though. What are your current pressures?
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Old 07-29-2018, 12:03 PM   #4
stormtown
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Re: what should my a/c pressures be for r-12

How do I get hold of Benny? I would like to talk to him about restoring my 72 AC/heater box
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Old 07-29-2018, 01:10 PM   #5
rx78nt1alex
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Re: what should my a/c pressures be for r-12

Here's his FB.
https://www.facebook.com/factoryautoair/
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