Another A/C question

[doclees]

I think I posted this in another section but didn't get much response.
I have 2 R12 systems to convert to 134a..maybe. efproducts.com says you don't need to open your system and remove the mineral oil before filling with 134a and PAC oil. Specifically states that GM says you do not need to change O rings.
on the other extreme I am told and read that you need to evacuate, flush, change the compressor, o rings and accumulator/dryer, reassemble and re-evacuate. Then recharge.
I think my GM system is just a little low on R12. If I could get an R12 charge at a reasonable rate I would just do that. My 93 SHO has a very rusty accum/dryer so I think changing that out is going to be necessary.
Is the truth out there? Can you do a successful and non-damaging closed system retrofit?
Doesn't make much sense to replace a working compressor.

 

[jelloslug]

I have done 12 retrofits over the years on several different makes. My personal current method is to replace all the o-rings (because they are most likely why it's low to begin with) and if it has sat open of any length of time replace the dryer. You should also replace 1/2 of the old oil with PAG. Make sure to vacuum it for at least an hour after you add the new o-rings, oil and other parts. This method had worked for the last 3 years on my '90.

 

[doclees]

OK let me recap your method. Evacuate, open system to change O rings, keep same dryer if only open a short time, vacuum for 1 hour, add 1/2 the systems recommended oil volume with PAG, charge with 134A. correct?

 

[jelloslug]

OK let me recap your method. Evacuate, open system to change O rings, keep same dryer if only open a short time, vacuum for 1 hour, add 1/2 the systems recommended oil volume with PAG, charge with 134A. correct?

You should really verify the oil level if possible before you add more oil. You need to replace half the oil, not add more oil. Other than that, that's exactly what I did.

 

[doclees]

So how do you verify the oil level?

 

[jelloslug]

So how do you verify the oil level?

AFAIK you pour it out of the compressor and measure it....

 

[doclees]

So now we need to remove the compressor? Why not replace all the old mineral oil with PAG? I thought the controversy was the compatibility of PAG and mineral oil?

 

[jelloslug]

So now we need to remove the compressor? Why not replace all the old mineral oil with PAG? I thought the controversy was the compatibility of PAG and mineral oil?

PAG and mineral oil are compatible. The controversy was with mineral oil and the R134 o-rings. The current school of though is replace at least[/]1/2 your oil with PAG and no matter what o-rings you have you will be OK. Personally I would just put in a little PAG to make sure it's topped off (especially if you have a visible oily leak at any fittings) and just skip the oil checking procedure all together. IMO the most important thing is the vacuuming of the system and then changing the old o-rings (not because of incompatibility issues, because they are old and brittle).

 

[doclees]

OK now it is coming together and making sense. I understand the purpose of vacuuming a system is to pull impurities out of the mineral oil. I understand that evacuating is just to recover the R12 or 134A. Correct?

 

[JustinSane]

they make conversion kits that allow you to convert r12 to r134, these kits come with oils and conditioners that allow the r12 system to work once filled with r134, they cost under 50 bucks and work very well. this is taking into account your r12 parts are in good working order.

 

[jelloslug]

OK now it is coming together and making sense. I understand the purpose of vacuuming a system is to pull impurities out of the mineral oil. I understand that evacuating is just to recover the R12 or 134A. Correct?

Evacuating is to pull out any remaining R-12. Vacuuming the system after you change any parts boils out any moisture that may have entered the system while you were working on it. I would consider it a mandatory step.

they make conversion kits that allow you to convert r12 to r134, these kits come with oils and conditioners that allow the r12 system to work once filled with r134, they cost under 50 bucks and work very well. this is taking into account your r12 parts are in good working order.

To really convert a system properly one of those kits are just some of the parts you need. You still need to vacuum the system and you still need to fix the leak that caused your R-12 system to need to be recharged in the first place.

 

[naval-avi8or]

I would suggets you do some research (on the internet) on R-134 retrofit/servicing. You will not only find a wealth of kowledge it will also give you the reasons to change out different items. Don't use a GM based site as GM had issues with R-12 compressors not being able to handle the higher pressure of the R-134. R-134 is not near as forgiving as R-12. By this I mean that you can't just charge it up to the manufacterer black and white number. The slightest amount of error can reduce its cooling factor in a non linear way. Same goes with the oil little to much and the compressor will work way to hard and therfore not cool as well. You can get by with just reclaiming the R-12 and as much oil as possible then service it with PAG/ESTER Oil and refrigerant but you should replace the high press cutout switch orings, expansion valve and its recommended that you replace the acc/dryer as well.

If your looking for the quickest method, just pick up a retrofit kit from autozone and it will have all you need to quickly get going minus changing any recomended stuff (connection adapters, freon and POE oil which is compatible with R-12/R134) and you would still need to purchase a R-134 High press cut out switch.

 

[I'll sho u]

Do not use pag oil! It is not compatable with the mineral oil in r-12 systems. Pag is for 134 only. When switching from r12 to 134 use ESTER oil.After a deep vacume replace half the sysetms oil charge with Ester and charge to 80 percent of the r12 charge then enjoy cold air once again. By the way I work in a radiator/ac shop.