[Tmiller]

Ok, my 70 has stock air. The car was off frame restored some years back. Ive never used the ac. I wanted to try using this year I hooked up the gauges and read zero so i did a vacuum on it ti start from scratch. The low port has the R-134 quick disconnect type. The high port has a screw on R-12 type valve. Top of gm compressor has lable saying R12 and specs. Im leaning toward R-12. Also no blue lable with conversion date. Any way to tell from here

 

[DZAUTO]

I cannot tell you how or what to look at to determine if your AC system is R12 or 134.
BUT, when I got our 70 conv in 98, it was still on R12. I worked on it as best as I could and it sorta kinda blew cold, but not like it should. I wanted to keep it on R12 (YA, YA, YA, YA, I Know, R12 is scarce and expensive). I removed and sent the whole system to Classic Auto Air in Tampa. I bought a flush kit and flushed the remaining system and installed a new dryer. Sometime in its past, the bracket in the center of the grill had been pushed back into the bottom tube of the condensor and worn a tiny hole which my radiator friend repaired. What was returned was a unit that looked like it just came from the Chevy Parts dept. That was in 2012. I have not added any R12 since and it blows 38-40 deg. I'm happy.

 

[B52bombardier1]

My prediction is that your system is R134A and is probably using a PAG compressor oil. Why else for the R134A low fitting? I would not go back to R12 because I think the two different oils for these refrigerants are not compatible.

I would also strongly consider changing the receiver-drier / accumulator.

Rick

 

[swampy 6x6]

hi
R12 performs better unquestionably no doubt !!
A good service will include the following

flush all components compressor condensor and evaporater and rigid pipe
pressure test for leaks compressor condensor and evaporater
if evap core is stained or very dirty replace
replace Tx vavle /ccot
replace receiver drier
replace at least discharge /high press hose and preferably suction hose
replace all o rings
reoil compressor
Add a 12 inch elec fan to front of condensor

 

[Tmiller]

I cannot tell you how or what to look at to determine if your AC system is R12 or 134.
BUT, when I got our 70 conv in 98, it was still on R12. I worked on it as best as I could and it sorta kinda blew cold, but not like it should. I wanted to keep it on R12 (YA, YA, YA, YA, I Know, R12 is scarce and expensive). I removed and sent the whole system to Classic Auto Air in Tampa. I bought a flush kit and flushed the remaining system and installed a new dryer. Sometime in its past, the bracket in the center of the grill had been pushed back into the bottom tube of the condensor and worn a tiny hole which my radiator friend repaired. What was returned was a unit that looked like it just came from the Chevy Parts dept. That was in 2012. I have not added any R12 since and it blows 38-40 deg. I'm happy.

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Can I did a little deeper on your situation. When you say the whole system, You mean, evaporator, condensor and compressor. I would love to stick with r 12. ( I am getting certified so i can but it) 20.00$. Thanks for the pics.

 

[Tmiller]

My prediction is that your system is R134A and is probably using a PAG compressor oil. Why else for the R134A low fitting? I would not go back to R12 because I think the two different oils for these refrigerants are not compatible.

I would also strongly consider changing the receiver-drier / accumulator.

Rick

Thanks, I tend to agree with you as to why else would there be a 134 fitting on the low port. Ill change the dryer, But I dont think I need a flush since i would be putting 134 back in

 

[O'Man]

hi
R12 performs better unquestionably no doubt !!
A good service will include the following

flush all components compressor condensor and evaporater and rigid pipe
pressure test for leaks compressor condensor and evaporater
if evap core is stained or very dirty replace
replace Tx vavle /ccot
replace receiver drier
replace at least discharge /high press hose and preferably suction hose
replace all o rings
reoil compressor
Add a 12 inch elec fan to front of condensor

R12 12 and R134 both perform well IF the systems they are installed in are working properly and configured properly. Yes R12 performs better in a system designed and built for R12 than than same system will perform when charged with R134.

Any of todays new cars are capable of generating duct temperatures as low as older stock configuration r12 charged systems because the r134 is running in a system designed & built for R134. R134 has different characteristics for taking on heat and giving off heat. The expansion, contraction and heat dissipation profiles are dissimilar for the two mediums.

You must have a system that is built accommodate those R134 characteristics. Adjustments to the POA valve are necessary to run 134 in older systems and a parallel flow condenser are key to getting 134 to perform up to its potential in these older cars.

Simply saying that r12 is better is a kinda broad brush generalization.

 

[Dean]

Ok, my 70 has stock air. The car was off frame restored some years back. Ive never used the ac. I wanted to try using this year I hooked up the gauges and read zero so i did a vacuum on it ti start from scratch. The low port has the R-134 quick disconnect type. The high port has a screw on R-12 type valve. Top of gm compressor has lable saying R12 and specs. Im leaning toward R-12. Also no blue lable with conversion date. Any way to tell from here

No way to know for sure what someone else did besides install a low side R 134 service port adapter. Maybe they just added R134 refrigerant and didn't change the refrigerant oil and maybe they did.

Here's what I would do if it were mine;
I would evacuate the system to a deep vacuum and see how long it takes to loose the vacuum. If the system stayed in a vacuum for a while, I would dump enough R-134 in to pressure test for a leak and if the leak is elusive enough I would add more refrigerant just to see how well it cools then go from there. (If I found the leak, naturally I would fix it)

If it seems to cool fairly well I would flush the system, change the refrigerant oil and the liquid line filter/drier and see how good it cools without changing the poa setting.

You'll have to decide which refrigerant you are going to go with before changing the oil but R134 is a lot cheaper.

 

[DZAUTO]

Can I did a little deeper on your situation. When you say the whole system, You mean, evaporator, condensor and compressor. I would love to stick with r 12. ( I am getting certified so i can but it) 20.00$. Thanks for the pics.

The car came from up north, so apparently the AC was not used as much as we do here in Okla/Tex. Thus, the compressor was in excellent condition. When I removed everything from the firewall and all the hoses, I capped off the compressor.
I bought a new main hose, which included the hose going out to the condenser and over to the POA valve. After I had the tiny hole repaired in the bottom tube of the condenser, I flushed it out along with the remaining tubing. I installed a new dryer with a sight glass.
I removed the entire unit from the firewall (requires removing the right inner fender), boxed it and shipped it. Classic Auto Air completely disassembled everything, rebuilt the POA valve, rebuilt the expansion valve, refinished everything like factory, and adjusted the POA valve for R12.
Basically, all I had to do was assemble everything, with new O-rings, vacuum the system and charge it. I left the vacuum pump on for 18hrs, shut it off and left it for 6hrs. the gauge NEVER moved. Then I charged it. It's been working perfect and blowing 38-40deg air since 2012.

Our 70 conv was a factory 307/3sp on the column.
I would love to have a BB, BUT, to change to a BB would require rounding up EVERYTHING for the conversion. I had some rebuildable SB400 cores, which would literally be a drop-in bolt-in swap. So I built a very healthy SB400 with a complete cowl induction setup and replaced the 3sp with a built M22W, and rounded up a floor shift steering column to get rid of the original column shifter knob. I have ZERO regrets!

 

[swampy 6x6]

HI
r134A high pressures are higher and low pressures are lower compared to R12.
Combine that with the fact most modern vehicles run small condensers and older vehicles use low efficiency condensers its no wonder R134a is challenged .

Evaporators
All the way upto the 90`s the cores were inefficient and to small .

R12 converted to R134a ---Gm car from the 70`s
An example is to run 180psi with 2 condenser electric fans plus factory clutch fan ,engine at fast idle ,vent temp40f , ambient 95f

Ford Ranger 2007--2015
290 psi factory on a 75f day slow or fast idle vent temps took at least 5mins to achieve , very ineffective
Repaired ,fitted 2nd condenser 150-160psi slow or fast idle on a 110f day , charge 100% with sight glass instead of weight charging . 45F vent temp very quick temperature pull down .

 

[Dean]

HI
r134A high pressures are higher and low pressures are lower compared to R12.
Combine that with the fact most modern vehicles run small condensers and older vehicles use low efficiency condensers its no wonder R134a is challenged .

Evaporators
All the way upto the 90`s the cores were inefficient and to small .

R12 converted to R134a ---Gm car from the 70`s
An example is to run 180psi with 2 condenser electric fans plus factory clutch fan ,engine at fast idle ,vent temp40f , ambient 95f

Ford Ranger 2007--2015
290 psi factory on a 75f day slow or fast idle vent temps took at least 5mins to achieve , very ineffective
Repaired ,fitted 2nd condenser 150-160psi slow or fast idle on a 110f day , charge 100% with sight glass instead of weight charging . 45F vent temp very quick temperature pull down .

But this is about 1970 Chevelle air-conditioning

 

[SSuper Dave]

The same principles apply though, parallel flow condenser and proper charge will make one work. I just did a '71 Sprint with factory air, used a parallel flow condenser with a recalibrated POA, charged with 48 oz R134A, which is 80% of the R12 charge, and I have 38.6 at the right vent. I use a machine to charge, after it was running on 48 oz, I added an oz with no change, added a second oz and the temps went up hair, so I know that on this car, 49 oz is my optimum charge. I did the same thing when I converted my '68 Caprice, 50 oz is the optimum charge on that car.

 

[billdini]

I am using R12a in my cars. It it more efficient, produces less head pressure and cools better then R12 or R134. It is flammable and therefore more dangerous then 12 and 134 but the newest R1234y is just as flammable and used in most new cars today. Actually Canada and Germany have used it for years however I should point out those systems are designed for it's use. I haven't decided if I will go to R12 at a later time once I know the system is tight however its likely. R134 no way. The good thing about this stuff it is compatible with seals and oil from both types of systems today so it is easy to change and it doesn't pollute at all unlike R12 and R134. Yes Dean I can hear you saying someone shut up that Dini guy. Hey it works!!

HC-12a - Wikipedia

en.wikipedia.org

ZEROR Universal AC Refrigerant (six) 6oz Cans 16oz R134a Replacement Made in US for sale online | eBay

Find many great new & used options and get the best deals for ZEROR Universal AC Refrigerant (six) 6oz Cans 16oz R134a Replacement Made in US at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Dean]

I am using R12a in my cars. It it more efficient, produces less head pressure and cools better then R12 or R134. It is flammable and therefore more dangerous then 12 and 134 but the newest R1234y is just as flammable and used in most new cars today. Actually Canada and Germany have used it for years however I should point out those systems are designed for it's use. I haven't decided if I will go to R12 at a later time once I know the system is tight however its likely. R134 no way. The good thing about this stuff it is compatible with seals and oil from both types of systems today so it is easy to change and it doesn't pollute at all unlike R12 and R134. Yes Dean I can hear you saying someone shut up that Dini guy. Hey it works!!

HC-12a - Wikipedia

en.wikipedia.org

ZEROR Universal AC Refrigerant (six) 6oz Cans 16oz R134a Replacement Made in US for sale online | eBay

Find many great new & used options and get the best deals for ZEROR Universal AC Refrigerant (six) 6oz Cans 16oz R134a Replacement Made in US at the best online prices at eBay! Free shipping for many products!

www.ebay.com

I was thinking about the Ford Ranger 2007--2015 statement.
There has been a lot of advancement to make air-conditioning more efficient since Mr. Carrier invented the electric air-conditioner in 1902 but the basic theory is pretty much the same.

Hey when I went to refrigeration and electrical school we had high side floats and Sulphur Dioxide systems, along with cap tube systems and belt drive compressor refrigerators and freezers to play with.
Keeping up with more modern systems requires a memory.
(which I do not have)😩

 

[swampy 6x6]

hi
Dean
The same principles apply to any car its all refrigeration .
R12
evaporators are inefficient
condensers were larger tube and fin and work far better with twin electric fans

R134a
evaporators are more efficient
condensers are more efficient but alot smaller in size typically . Called parallel flow units . Large units are available.

The key is to run as low a pressure as possible on the high pressure side ie 150psi
R12 in industry did run this pressure in the 70`s
Automotive manuals do a pressure vs ambient chart 70F ambient is 150psi high side

1/ THE LOWER THE hIGH PRESSURE =THE LOWER THE TEMPERATURE OF REFRIGERANT FEEDING THE EVAP CORE= colder vent temps
2/ THE LOWER THE HIGH PRESSURE = THE SYSTEM THEN CAN BE FULLY CHARGED
EVAP HATE BEING FED GAS AND LIQUID MIX FROM CAUSED BY UNDER CHARING
3/ UNDER CHARGING IS CAUSED BY HAVING EXCESSIVELY HIGH HEAD PRESSURES WHICH LIMIT CHARGING CAUSED BY A SMALL CONDENSOR

this applies to all airconditioning and refrigeration

 

[Tmiller]

hi
R12 performs better unquestionably no doubt !!
A good service will include the following

flush all components compressor condensor and evaporater and rigid pipe
pressure test for leaks compressor condensor and evaporater
if evap core is stained or very dirty replace
replace Tx vavle /ccot
replace receiver drier
replace at least discharge /high press hose and preferably suction hose
replace all o rings
reoil compressor
Add a 12 inch elec fan to front of condensor

I have since done all you suggest. I stayed with r-12 and blowing cold ass air. Thanks for the suggestions. Found r-12 on fb. A buddy sent it to me for free.

 

[swampy 6x6]

hi
full service is generally required on most vehicles between
65000 miles to 130,000miles depends on the operating environment .
This is for reliable operation

Well done for giving your A/C a good birthday .