View Full Version : Automotive refrigerant question

02-08-2016, 01:19 AM
Hello everybody, I'm brand new to this sight and had a couple questions for you since I am unable to find the information elsewhere.... I have a 1993 dodge pickup that has an R12 refrigerant system in it that does not blow cool air at all, and trying to find R12 without spending a mini fortune is almost impossible. I'm wondering, if I draw the entire system under full vacuum, and recharge with R134a, will that be sufficient in removing all the mineral-based oil from the system?? I do not want to replace the system components to accept 134a just for air conditioning and to my understanding the "stand-in" refrigerant doesn't work worth a hoot. And, if not, I'll just spend the money on the R12 and recharge that way. In that case, can you tell me the weight of liquid needed in a fully evac'd system and the operating pressures across the pressure and vacuum sides?

Ok, a little background information about myself; I am a union pipefitter apprentice that works with a plethora of refrigeration service mechanics so I have a really good grasp of how said units operate, oils required, kinds of refrigerants, pressures, etc. I will be doing all work myself and completely understand all safety needed, equipment use, etc. I hope this question has not been asked before but any and all information on this is extremely appreciated!! Thank you all in advanced.

02-08-2016, 03:32 AM
Change the oil to ester oil in the compressor,then charge it with 134a

02-08-2016, 10:36 AM
1993 American vehicle. There should be an A/C charge weight in the engine bay or in the Vehicle Manual.
Check the A/C flexible hoses for writing that could say R12. Most R12 hoses have pressure release Indents.

R134a will leak from these. Found out the hard way back when i converted a Jaguar V6 to 134A :(

02-08-2016, 11:44 AM
That's part of my question, is just pulling a complete vacuum on the system enough to remove all the mineral oil so I can replace with the ester oil? Thank you for the info about the pressure release indents. How did you stop them from leaking?

02-08-2016, 02:06 PM
Best thing to do is take off the compressor, empty it to a can, fill up the same amount + 10% poe oil, repjace all the flexible rubber hoses.

Once the compressor is out, check if there's a leak from the shaft seal.
Good luck.

02-08-2016, 03:33 PM
Vacuuming the system will not remove the oil, only draining the compressor will achieve that, sorry.

02-08-2016, 04:11 PM
Hi Fitter2008
Welcome to the forum.
As Mikeref and other have stated you need to replace all your flexible hoses.
As was explained to me by an instructor who knew better than me.
You need to change the hoses because the Refrigerant molecules within the R134a are smaller than the ones in R12.
So a gastight R12 Hose will leak like a sieve when it contains R134a.
I like others have made that mistake.
Also when I converted an Ice-cream Van to R134a Iseon (R134a Manufacturers) Advised me to charge the system by the weight on the Data Plate Less 10%!
Its worked for me, reason being the system runs at slightly higher Condensing pressures I believe?
Good Luck

02-08-2016, 08:38 PM
So, if I were to replace any rubber/flexible lines, remove compressor & turn it upside down to drain oil (via the pressure/suction ports on top I assume) and flush it with approved "flush-style" solvents, refill with ester oil of equal volume minus 10%, reassemble system, vacuum, and recharge with R-134a refrigerant, I should be good?? That sounds to be the easiest plan of attack actually. Please somebody with much more experience than I verify that I have this understood correctly.

charlie patt
02-08-2016, 09:12 PM
As cad says change oil in comp in a hot climate I would use poe 100 you do not need to change hoses if u are using a .....a ..... ie 134 refrigerant so if your using r134a pull comp change oil if it has a suction accumulator remove and drain pull good vac drop in r134a of you go it won't be quite as efficient as 12 but the closest you will get to 12
If you are changing to a b refrigerant then you would change pipes dodge use a c type maullie hose which is compatible with mineral or ester

03-08-2016, 02:12 AM
I got it. I have the oil on order and I will be working on it within the next 2 weeks.... Random question for you all; what's the cooling potential/efficiency if I were to you R-410a in this system compared to R-134a?? They're both a refrigerants so the oils should have the same compatibility. Or would the operational pressures required with 410a be higher that the abilities of a typical automotive application??

03-08-2016, 04:00 AM
Use only 134a,

03-08-2016, 12:06 PM
Don't even consider R410A as the compressor and all of the component parts are not designed to work on or withstand the potential pressures.

03-08-2016, 06:14 PM
I'm not considering using 410a by any means..... Just just asking purely from an academic standpoint... Everyone here has already helped me greatly. I have products on order and will be working on it within the next two weeks. Thanks again!

05-08-2016, 08:26 PM
Alright, I started working on the air conditioning system on my truck to do a preliminary check for any leaks, and I found a R-12 to R-134a adapter on the high side already there from the previous owner.... Now, that arises a couple questions I don't know the answer to;

1- if the previous owner just got an adapter and recharged with R-134a without swapping oil and doing things properly, could that have damaged anything internally with the compressor from the incompatibility of *****/oil combination??

2- the low side port is smaller and my gauge set won't fit. So, that leads me to believe either I do not need to pull a vacuum on that side of the system because it makes a loop, or, I need an adapter.

3- What's the 12a refrigerant I keep seeing advertised when I search R-12? Is that fully compatible with existing R-12 if I decided not to pull compressor??

Many thanks!