What's new
By:
Filters

R-12 auto A/C tech in chit chat

plym49.2

plym49.2

Sasquatch49.2
Joined
May 20, 2020
Member Number
550
Messages
440
The A/C in my 1988 K1500 that I purchased new in 1987 has been out for a while.

A bunch of years ago the compressor started making noise. At the time I was mostly using the vehicle in Vermont so it was no big deal.

A couple-three or four years ago I headed South so I needed the A/C working again. I had a buddy, who has run a very good auto repair business for almost 50 years, do the work for me up north. He installed a new compressor, new receiver dryer, and whatnot. I had a full jug of R-12 so we kept it an R-12 system. He recalls using regular R-12 oil.

The system worked well for a while and then started losing refrigerant. I replaced the Schroeder valve cores. I topped it up and it lasted a few weeks. I went to top it off again to see if I could find the leak and ended up blowing the o-ring at the connection head on the back of the compressor. One bolt holds the manifold in place and there are two o-rings underneath, inlet and outlet. My buddy said that he had a hard time sourcing the correct o-rings because the new replacement compressors were different or something. Neither of us recall the details.

My buddy would gladly straighten it out for me but we are now 1000s of miles apart. In the interim I have had no a/c in the vehicle. I would now like to get the a/c going again.

I don't know if the o-ring was the leak and it got worse or if there is another leak somewhere else. I am now in a place where I do not know any shops and suspect that most of them do not know R-12 systems anyway. I am also running low on R-12.

What are the pros and cons for these options:
  1. Replace the o-rings and keep it R-12. But if leaks persist I will run out of R-12. Is there R-12 leak dye any more?
  2. R-134a conversion. But what about the R-12 lube and the fact that R-12 system pressures are not right for R-134a? What other stuff would I need to do?
  3. Bacon.
I have gauges. I would prolly purchase a HF vacuum pump (they have 2 models - is the less-expensive one any good?).

My friend who originally did the work says that I would need to flush out the R-12 lube and replace the receiver dryer if I was going to convert. Another mechanic friend of mine - also in business for 40 years - said that nowadays you just evacuate and refill with R-134a and that's all that is needed. Could it be that simple, and if so what are the potential gotchas?
 
at work we dump in 134 with PAG oil
don't worry about the left over mineral oil from the r12
it works fine

what I do on my own shit is to break the vacuum with propane, then charge with 134, the propane carries the mineral oil through the system
it also works fine, just less... approved by the powers
 
Do the conversion!


If the cheaper pump was any good there wouldn't be a more expensive version of if it.



Stop being a cheap fawk and fix it right.
 
It's got the pancake pump and is probably leaking around the shell. Convert it to r134 it'll be fine.
 
[486] said:
at work we dump in 134 with PAG oil
don't worry about the left over mineral oil from the r12
it works fine

what I do on my own shit is to break the vacuum with propane, then charge with 134, the propane carries the mineral oil through the system
it also works fine, just less... approved by the powers
Click to expand...
What fittings are needed to connect a propane tank? I have a full 15.5 oz tank of Coleman butane/propane mix for a camp burner. That should be enough for a flush, yes? So you pump it down, connect the propane, and pump it down again?

I know that a propane/butane mix is workable but I don't think the Coleman ratios are correct. I have no problem running propane, butane, or swamp gas.
 
M92PV4U said:
It's got the pancake pump and is probably leaking around the shell. Convert it to r134 it'll be fine.
Click to expand...
Yes, it is the pancake pump. It is new for what that is worth. A couple of years ago I added 134a stop leak to a 1995 vehicle and that has been just fine ever since.
 
where are you located?
134 swap, but also works better with an added electric fan, and the serpentine style condensor.
 
plym49.2 said:
What fittings are needed to connect a propane tank? I have a full 15.5 oz tank of Coleman butane/propane mix for a camp burner. That should be enough for a flush, yes? So you pump it down, connect the propane, and pump it down again?

I know that a propane/butane mix is workable but I don't think the Coleman ratios are correct. I have no problem running propane, butane, or swamp gas.
Click to expand...
what

install pag oil into dryer (iirc those old GM ones were one of the very few that call for the 150 viscosity, but 100 or 46 will probably be just fine), attach all the hoses and shit
vacuum
break vacuum with propane
charge with 134 until it makes enough cold with max blower

r12 fittings are just 1/4" flare, you can figure out the propane tank to that if you aren't dumb
don't bother with disposable cans or butane stuff
the butane would work better for carrying the oil but it is going to be harder to adapt so...
 
Last edited:
plym49.2 said:
Yes, it is the pancake pump. It is new for what that is worth. A couple of years ago I added 134a stop leak to a 1995 vehicle and that has been just fine ever since.
Click to expand...
I replace the one in my dad's '89 blazer every 4-5 years it starts to leak.

I did the conversion on a '89 extra cab c3500 new dryer, pump and orfice tube flushed everything else add pag oil and r134, it works great. I used a scale to measure the amount of r134 that I used.
 
Jason4x4 said:
where are you located?
134 swap, but also works better with an added electric fan, and the serpentine style condensor.
Click to expand...
Central TX. I have auxiliary electric fans already. Motor has the serpentine belt.
 
I hear Duracool works as well as R12 and it's fairly cheap.
 
unless it's hammered dog shit:laughing:

I just assumed you cared about it and it was cherry. But maybe you're one of those guys that wants his money's worth:flipoff2:long bed extra cab 4.3 5speed 4 mismatched 245s, top post yard sale battery with auto zone adaptors, bed cut for the fuel pump, half inch door sag....

Fucking run 134, propane, butane, whatever:laughing:
 
[486] said:
at work we dump in 134 with PAG oil
don't worry about the left over mineral oil from the r12
it works fine

what I do on my own shit is to break the vacuum with propane, then charge with 134, the propane carries the mineral oil through the system
it also works fine, just less... approved by the powers
Click to expand...
What do you mean by "break the vaccum"

For someone getting the little pressure cans of lubricant from Walmart instead of working out of a gallon jug in a shop environment what's the purpose of "breaking the vacuum". I can see why you'd want to get the system to atmospheric pressure if you're gonna pour oil in with a funnel. I typically just pressure test for leaks, vacuum, confirm it's still not leaking, then hook up one of those little cans of lube followed by a can of R134.
 
Another tip: Replace the condenser with one from a 1994 model. Those are slightly larger to account for the additional cooling needs of the 134a. Make sure you add 10% less R134 than the system calls for, as the R12 weighs 10% more.

Oh, yeah... the pressure switches are interchangeable as well, so grab those from the 94, too.
 
  1. Replace the o-rings and keep it R-12. But if leaks persist I will run out of R-12. Is there R-12 leak dye any more?
  2. R-134a conversion. But what about the R-12 lube and the fact that R-12 system pressures are not right for R-134a? What other stuff would I need to do?
  3. Bacon.
1. I have the o rings sitting in my toolbox. There’s a ton of adaptor o rings depending on exactly what updated compressor you have (there were several updates). A pic of the line separated from the comp so I/we can see what else are dealing with would be best. A lot of the adaptor o rings/seal never worked exactly right, but worked.
2. I would do the conversion though. I was at the dealer when this all came about, so I’m familiar with it. The 2 oils are but are not compatible. Basically, GM recommended replacing the accumulator (trying to remember if the orfice needed replacement too, I don’t think so though) and flushing out as much oil as possible. You can flush the lines with denatured alcohol and compressed air. If you feel frogs, pull the compressor and try to dump any oil that’s in there too. Then you add in the r134a oil. There was a big mathematical equation GM had for the conversion for the amount of Freon needed. Basically, it was .5# less :homer:
3. mmmmmmmmmbacon. Aaaaahhhhhh
 
I would just vacuum it and charge it with 134 it from cans. You can get a can with oil and dye in it. Then use a blacklight to find the leak When it leaks out.

Many shops have a big AC O ring assort box for matching up odd stuff. You can usually look up the dimensions online but sometimes it’s compare and guess. If you get dimensions I’ll look at my O rings.
 
The low pressure cutout switch. When you convert to R134 back it off about a turn to 1.5 turns. So the cutout is down around 10 psi. It helps keep the pressures down and gets colder. .

But yeah convert. Won't be long and R134 will be the new R12 with the 1234yf coming.

Right now you can buy 30lb R134 for $80. Everyone should grab a few.

Air powered vac pump from harbor freight is fine. Just leave it on there as long as your compressor will allow.

Old oil is fine.
 
Tiha said:
But yeah convert. Won't be long and R134 will be the new R12 with the 1234yf coming.

Right now you can buy 30lb R134 for $80. Everyone should grab a few.
Click to expand...
I had to buy one recently, I think it was 130ish at the supply house, where you finding them for $80?
I was thinking about buying a spare
 
Projectjunkie said:
I had to buy one recently, I think it was 130ish at the supply house, where you finding them for $80?
I was thinking about buying a spare
Click to expand...
He lives in Minnesota and you in Arizona so their may be a difference based on supply and demand. They go on sale here in Pennsylvania for $80 a couple of times a year.
 
True

Any particular chain? I get a break at the supply house, but not enough business to get the best pricing
 
Projectjunkie said:
I had to buy one recently, I think it was 130ish at the supply house, where you finding them for $80?
I was thinking about buying a spare
Click to expand...
Truck parts places don't have the same mark up as auto parts.

Most truck supply places run specials. Right now it is Freightliner dealer that has it for $80 a jug.
Next month it will be Kenworth.

Next November it will be International.

Places like American radiator, or midwest radiator will run specials. There is probably similar business close to you. Just gotta call around. I remember seeing it go as high as $400 a jug in high demand summers. So I always grab a few when the price is around this.
 
  • Like
Reactions: DMG
Tiha said:
Won't be long and R134 will be the new R12 with the 1234yf coming.

Right now you can buy 30lb R134 for $80. Everyone should grab a few.
Click to expand...
There's no reason to be stocking up on refrigerants as long as propane is readily available.
 
Anyone remember when they were bringing R12 in from Mexico that was "blended" with propane and it was turning AC systems into bombs?

Yeah that was fun.

I have tried a few different drop in replacements. At the end of the day just convert it and make the best of it. No R134 doesn't work as well in a R12 system but it is cheap and you can do some things to improve performance.
Had a surburban I converted. It would get to 40 degrees but it needed a new compressor about every year because the pressures were just too high.
So live with 50 degrees and everything will last longer.
 
Ester oil & 134 low side conversion fitting is my go to.
Fix what's leaking, spin on low side fitting, pull and hold vac, add some ester oil & charge to 80% of the original capacity. I've had really good luck doing it this way. Probably do 3 or so cars a year
 
[486] said:
oh noes the sparks from the brushes in your brushless compressor motor are gonna light up the magical flammable gas that can burn in an oxygen free environment
Click to expand...
LOL, I agree, I have no idea how they ignite, but the videos, and warnings, and media sure made a big deal of it.

I am sure it was more of a guy smoking while venting the system to atmosphere or maybe the condenser getting opened up during an accident.
 
LSxFJ said:
Ester oil & 134 low side conversion fitting is my go to.
Fix what's leaking, spin on low side fitting, pull and hold vac, add some ester oil & charge to 80% of the original capacity. I've had really good luck doing it this way. Probably do 3 or so cars a year
Click to expand...
That 80% is a great start. It is properly charged when the inlet and outlet of the evaporator are the same temperature.

Original capacity gets thrown off so far by different hose size and lengths. Or different oil charges.

We hardly fix leaks anymore unless they are really bad. Cheaper just to top it off. If it will run the summer on one or two fill ups then we leave it. Not worth fixing.
 
You must log in or register to reply here.
Top Back Refresh