AC capacities needed and other questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Rufas · 10-22-2019, 08:55 PM

I'm finally starting to get the factory A/C in my 1970 GMC back together. The only thing not original is the 508 Sanden compressor. The POA valve has been replace with the POA delete tube years ago. Would it be worth it to go back to a POA valve? They are available rebuilt but are pricey.

I need the coolant capacity of the system. I haven't decided just yet if I'll go with R12 or R134. Since I live in AZ, I want to get as much cooling as possible out of the system. So I'm leaning on using R12. R12 is still available for $20/$30 a can on eBay.

TIA

**Stocker** · 10-22-2019, 10:57 PM

Per my notes from a couple years ago when I had a shop resurrect my factory A/C system:

R12 takes 3.75# (60 oz) + 10 oz oil.

R134a takes 80% of the R12 amount, so 48 oz.

That's all the info I have..... hope it helps.

I went with R134a, but these things were designed to use R12, and I understand it cools better. Since you have a source, that's probably the best choice.

**FirstOwner69** · 10-23-2019, 01:23 AM

The original label on my '69 said 3.25#.The amount was on a stick on label that looked like something from a Dymo label maker. Underneath it said 3.75#. The label went missing years ago, but I found the same label on a junkyard compressor. That label is now on my truck. I've always wondered if later years took 3.75 since they changed to crimped hoses sometime later than my truck was made.

Just looked at the '69 service manual. It says 3 lbs. 4 oz. of R-12 and 10 oz. of oil. Do you have a manual for your year?

Rufas · 10-23-2019, 01:57 AM

Quote:

Originally Posted by FirstOwner69

The original label on my '69 said 3.25#.The amount was on a stick on label that looked like something from a Dymo label maker. Underneath it said 3.75#. The label went missing years ago, but I found the same label on a junkyard compressor. That label is now on my truck. I've always wondered if later years took 3.75 since they changed to crimped hoses sometime later than my truck was made.

Just looked at the '69 service manual. It says 3 lbs. 4 oz. of R-12 and 10 oz. of oil. Do you have a manual for your year?

Sure wish I did.

BTW here is a photo shortly after my Dad purchased this truck new in 1970.

After my restoration.

**FirstOwner69** · 10-23-2019, 10:15 AM

Quote:

Originally Posted by Rufas

Sure wish I did.

Nice truck!

Here's a link to PDF service manuals.
http://67-72chevytrucks.com/vboard/s...d.php?t=558016

10-22-2019, 08:55 PM	#1
Rufas Registered User Join Date: May 2016 Location: Fort Mohave, AZ Posts: 370	AC capacities needed and other questions I'm finally starting to get the factory A/C in my 1970 GMC back together. The only thing not original is the 508 Sanden compressor. The POA valve has been replace with the POA delete tube years ago. Would it be worth it to go back to a POA valve? They are available rebuilt but are pricey. I need the coolant capacity of the system. I haven't decided just yet if I'll go with R12 or R134. Since I live in AZ, I want to get as much cooling as possible out of the system. So I'm leaning on using R12. R12 is still available for $20/$30 a can on eBay. TIA __________________ 1970 GMC 2500 700R Trans, RideTech 4 link rear suspension, air bagged on all four corners, factory upper/lower A-Arms, 2 inch drop spindles. 350 SBC 300hp Weiand Supercharger FiTech 30004 EFI

10-22-2019, 10:57 PM	#2
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,728	Re: AC capacities needed and other questions Per my notes from a couple years ago when I had a shop resurrect my factory A/C system: R12 takes 3.75# (60 oz) + 10 oz oil. R134a takes 80% of the R12 amount, so 48 oz. That's all the info I have..... hope it helps. I went with R134a, but these things were designed to use R12, and I understand it cools better. Since you have a source, that's probably the best choice. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

10-23-2019, 01:23 AM	#3
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,852	Re: AC capacities needed and other questions The original label on my '69 said 3.25#.The amount was on a stick on label that looked like something from a Dymo label maker. Underneath it said 3.75#. The label went missing years ago, but I found the same label on a junkyard compressor. That label is now on my truck. I've always wondered if later years took 3.75 since they changed to crimped hoses sometime later than my truck was made. Just looked at the '69 service manual. It says 3 lbs. 4 oz. of R-12 and 10 oz. of oil. Do you have a manual for your year?



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