what should my a/c pressures be for r-12 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**bautino95** · 07-29-2018, 12:10 AM

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

engineer_gregh · 07-29-2018, 08:47 AM

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.

**Steeveedee** · 07-29-2018, 11:23 AM

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?

stormtown · 07-29-2018, 12:03 PM

How do I get hold of Benny? I would like to talk to him about restoring my 72 AC/heater box

rx78nt1alex · 07-29-2018, 01:10 PM

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

07-29-2018, 12:10 AM	#1
bautino95 Active Member Join Date: Feb 2016 Location: vallejo, ca Posts: 160	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

07-29-2018, 08:47 AM	#2
engineer_gregh Registered User Join Date: Feb 2012 Location: Smyrna TN Posts: 1,153	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. __________________ 1971 Longbed BB Cheyenne Super 1972 Longbed SB Cheyenne Super 1972 Longbed Highlander Custom Deluxe 1975 K5 4x4 full convertible Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=645165 Greg Smyrna TN

07-29-2018, 11:23 AM	#3
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,724	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? __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

07-29-2018, 12:03 PM	#4
stormtown Registered User Join Date: Jul 2018 Location: morristown, tn Posts: 66	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

07-29-2018, 01:10 PM	#5
rx78nt1alex Registered User Join Date: Jul 2013 Location: CEDAR HILL, TX Posts: 43	Re: what should my a/c pressures be for r-12 Here's his FB. https://www.facebook.com/factoryautoair/ __________________ 1968 Chevrolet Fleetside C-10 1971 Chevrolet Fleetside C-10



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