R-12 refridgerant to 134

[sqaurebodyrestore]

I have a 1986 GMC Jimmy with front AC only. I just replaced all components and checked system for leaks by evacuating system.

I need to know two things.

1. How many pounds of R-12 is used in the system. (The sticker from side of evaportator box is missing)

2. What percentage of that do I use if I am using 134?

Thanks for any help that I can get!

 

[Rusty Nail]

If you are converting the AC, you need to change a few components also.
You know that, right?
I'm thinkin dryer, condenser, and orifice tube is required for 134A.
Likely the same amount to switch. It's not much..but I dunno how much juice. Aint but a couple pounds....2.2?

Not really interested in AC - Ive always let another tech have those jobs...but I converted my IROC.

Hope this helps!

 

[RoryH19]

When I converted my R10 to 134, I replaced every component as they there 30+ years old.
Compressor, orifice tube, condenser, dryer, hose and evaporator.
As far as Freon, you need ~ 80 - 85% of the R12 amount.

 

[1987 GMC Jimmy]

The condensers of today are made to accommodate R134a better, but changing them is optional. Flushing is not. I run the OEM condensers in all my factory R12 vehicles, and they get pretty darn cold in the summer. They’d do a little better with a new condenser, but I still prefer the serviceability of the old condensers versus a degree or two less at the vents.

Harrison says 3.25 pounds of R12. People will say varied things for the percentage of refrigerant. I did 38 oz. of R134a and 7 oz. PAG 150. It worked beautifully, but keep in mind I got a new compressor. If you’re using your old one and does take a charge, I give it anywhere from a week to 18 months before the seals give out. It’s just the nature of the R4. Sitting is the worst thing they can do.

Looking back, it looks like I did 75% of the original charge. I don’t know why I did that because I’ve pushed it closer to 85% on subsequent jobs. Maybe I was scared that the little R4 would blow up, and I didn’t wanna stress it out.

 

[RecklessWOT]

DON'T CONVERT TO R134a FOR THE LOVE OF GOD!

You can still find R12 if you look hard enough. Cool part about R12 is that it actually works. The few vehicles that I've owned that have been converted sucked (including my current Burb), most you'll get out of that thing is "cool" air for a while. On new stuff that is designed for R134a it is sufficient, but for old stuff that should have R12 it doesn't really do a great job IMO

 

[gmbellew]

DON'T CONVERT TO R134a FOR THE LOVE OF GOD!

You can still find R12 if you look hard enough. Cool part about R12 is that it actually works. The few vehicles that I've owned that have been converted sucked (including my current Burb), most you'll get out of that thing is "cool" air for a while. On new stuff that is designed for R134a it is sufficient, but for old stuff that should have R12 it doesn't really do a great job IMO

My 1990 suburban has been converted to R134a and works very well as long as you are consistently moving 35mph or faster. Cooling performance drops rapidly at idle or in stop and go traffic. I plan to add an aux cooling fan this spring to see if that helps in the summer. If not, I'll wait for a major component to die before I make bigger changes, like a new condenser, compressor, etc.

 

[sqaurebodyrestore]

Thanks for all of your advice and comments.

I already replaced the whole system with new components except the compressor. I had a retired GM mechanic replace the seals in the compressor. So everything is new and has been evacuated. I them pressurized the system to make sure it held pressure and it does so far. Tomorrow if gauges are same as today, I will evac again and be ready to charge. I did contact a GMC dealer and an experienced service advisor told me the original system called for 2.25 pounds of R-12 and that I could use from 75 to 80% of that if it was converted to R134A.

Hopefully the gauges are good tomorrow. Charging air is last mechanical issue I need to take care of before I take to paint shop!

thanks again to all of you.

 

[AuroraGirl]

Have you considered alternative refrigerants?

R152a and R401a. second is an R12 drop in replacement, but nearly no ozone damage potential. less than R134a. First commonly runs at lower pressures, but im not sure on its other properties.

 

[1987 GMC Jimmy]

Thanks for all of your advice and comments.

I already replaced the whole system with new components except the compressor. I had a retired GM mechanic replace the seals in the compressor. So everything is new and has been evacuated. I them pressurized the system to make sure it held pressure and it does so far. Tomorrow if gauges are same as today, I will evac again and be ready to charge. I did contact a GMC dealer and an experienced service advisor told me the original system called for 2.25 pounds of R-12 and that I could use from 75 to 80% of that if it was converted to R134A.

Hopefully the gauges are good tomorrow. Charging air is last mechanical issue I need to take care of before I take to paint shop!

thanks again to all of you.

3.25 is original charge. You definitely addressed the main issue of the R4. Hopefully it’s not anymore noisy than normal and you get good use out of it.

 

[Rusty Nail]

Dang!
2.2

Word up.
(I just did this)

 

[jjester6000]

Some say that if you flush the system, you can fill it up with 134a/ester oil, and it will work, but other problems may arise.

 

[Doppleganger]

I know guys who are getting 35F at the vents on old York compressors with this stuff.

https://www.autorefrigerants.com/

 

[RecklessWOT]

My 1990 suburban has been converted to R134a and works very well as long as you are consistently moving 35mph or faster. Cooling performance drops rapidly at idle or in stop and go traffic. I plan to add an aux cooling fan this spring to see if that helps in the summer. If not, I'll wait for a major component to die before I make bigger changes, like a new condenser, compressor, etc.

Exactly. My 87 Burb was also professionally converted about a year before I bought it. I haven't used it in years, I don't think it even works anymore because I haven't bothered recarging it. The first summer I had it when it was nice and fresh If I was going 60mph it worked alright, kept the truck "cool". But at those speeds so does rolling the windows down. When I'm at a crawl in a traffic jam or just going light to light in a more populated area it did nothing whatsoever, and I would bake to death inside the damn thing.

ESPECIALLY in a Suburban that doesn't have rear A/C, with the sun beating down on those 147 linear feet of un-tinted windows like a big greenhouse made out of magnifying glasses the poor thing couldn't even stop the heat from rising in the cab let alone cool it down. Better to just roll all the windows down and stick your head out to gasp for air

 

[Rusty Nail]

Exactly. My 87 Burb was also professionally converted about a year before I bought it. I haven't used it in years, I don't think it even works anymore because I haven't bothered recarging it. The first summer I had it when it was nice and fresh If I was going 60mph it worked alright, kept the truck "cool". But at those speeds so does rolling the windows down. When I'm at a crawl in a traffic jam or just going light to light in a more populated area it did nothing whatsoever, and I would bake to death inside the damn thing.

ESPECIALLY in a Suburban that doesn't have rear A/C, with the sun beating down on those 147 linear feet of un-tinted windows like a big greenhouse made out of magnifying glasses the poor thing couldn't even stop the heat from rising in the cab let alone cool it down. Better to just roll all the windows down and stick your head out to gasp for air

Great post!

 

[gmbellew]

Exactly. My 87 Burb was also professionally converted about a year before I bought it. I haven't used it in years, I don't think it even works anymore because I haven't bothered recarging it. The first summer I had it when it was nice and fresh If I was going 60mph it worked alright, kept the truck "cool". But at those speeds so does rolling the windows down. When I'm at a crawl in a traffic jam or just going light to light in a more populated area it did nothing whatsoever, and I would bake to death inside the damn thing.

ESPECIALLY in a Suburban that doesn't have rear A/C, with the sun beating down on those 147 linear feet of un-tinted windows like a big greenhouse made out of magnifying glasses the poor thing couldn't even stop the heat from rising in the cab let alone cool it down. Better to just roll all the windows down and stick your head out to gasp for air

I have rear AC...it definitely helps even out the cab. Can't imagine how bad it would be without that! I feel for you, man....

When I was a kid, we had a suburban with no AC....windows down all the time!