R12\R134 mix.....

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R12\R134 mix.....

Postby DodgeFreak » Thu May 21, 2015 5:06 pm

My crewcab's air isn't working it is low on refrigerant. My dad doesn't remember if he filled it with R12 or R134A. I'm 90% it was with R12....how bad would it be if I drained the rest of the 12 out and refilled with 134 with out changing the dryer or anything??
92 D350 Cab and Chassis. Auto stock, wiring gremlins. 330k miles
92 W250 Ext cab rotted completely out. Auto, pump maxed, 215 ppump nozzles, Denny T2 pin.
85 D350 single wheel, converted to cummins, getrag, turned up 2 turns and afc screw flush.
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Re: R12\R134 mix.....

Postby ellis93 » Thu May 21, 2015 6:17 pm

If you can get past the whole freak show "you gotta swap everything out" stuff that's been circulated for years then do it. When I first bought my truck.....it had 12 in it. It got low and I did the same thing your asking about. The system lasted another 3yrs before the expansion valve took a dump and wouldn't close up to make cold air.

Roll the dice....there's no need to swap out oil between the two gases (proven fact) so I doubt changing the dryer is necessary,other than just a CYA measure.
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Re: R12\R134 mix.....

Postby DodgeFreak » Thu May 21, 2015 6:22 pm

Thanks! That's what I was thinking/hoping to hear.
92 D350 Cab and Chassis. Auto stock, wiring gremlins. 330k miles
92 W250 Ext cab rotted completely out. Auto, pump maxed, 215 ppump nozzles, Denny T2 pin.
85 D350 single wheel, converted to cummins, getrag, turned up 2 turns and afc screw flush.
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Re: R12\R134 mix.....

Postby DodgeFreak » Wed May 25, 2016 10:42 pm

I'm replacing the expansion valve, air dryer and I'm going to flush the condenser and evaporator. I was wondering how much oil I should add since I will be technically replacing all 4 items.
92 D350 Cab and Chassis. Auto stock, wiring gremlins. 330k miles
92 W250 Ext cab rotted completely out. Auto, pump maxed, 215 ppump nozzles, Denny T2 pin.
85 D350 single wheel, converted to cummins, getrag, turned up 2 turns and afc screw flush.
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Re: R12\R134 mix.....

Postby b4autodark » Thu May 26, 2016 5:05 am

I have added R134 to R12 systems on a bunch of old cars and trucks I've owned over the years with good results, never drained a system completley and refilled though.
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Re: R12\R134 mix.....

Postby Cburb » Mon Jul 25, 2016 2:58 pm

R12 uses mineral oil r134 uses PAG...they are not miscible with eachother, which means they will be separated and very very little lubrication will be occurring. not to mention just very small amounts of r12 in a system will raise the head pressure higher than it should be with 134.

The 134 with mineral oil wont circulate like it should and will just migrate to low spots and sit, very hard on the compressors since the oil isnt going to be flowing with the refrigerant.

You really should recover everything, change filter drier then at least remove compressor and drain old mineral oil and add some pag, then blow the lines with nitrogen, pull into a deep micron vacuum and you should be set. Could change o rings while your at it and youll have a solid system. Otherwise you are just rolling the dice and not going to have a properly working system and wont last as long as it could.

If you dont feel like doing that then just get some 414b hotshot and charge with that, at 80% of the factory charge, its compatible with mineral and works fine.

I really dont care if people have done this with no problems, you cant argue science its still not right but some compressors are tougher then others. It could run fine for a while, then again maybe not. At a minimum it will definitely not last as long as it could and wont be as efficient either.
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Re: R12\R134 mix.....

Postby BC847 » Mon Jul 25, 2016 4:09 pm

Cburb wrote:R12 uses mineral oil r134 uses PAG...they are not miscible with eachother, which means they will be separated and very very little lubrication will be occurring. not to mention just very small amounts of r12 in a system will raise the head pressure higher than it should be with 134.

The 134 with mineral oil wont circulate like it should and will just migrate to low spots and sit, very hard on the compressors since the oil isnt going to be flowing with the refrigerant.

You really should recover everything, change filter drier then at least remove compressor and drain old mineral oil and add some pag, then blow the lines with nitrogen, pull into a deep micron vacuum and you should be set. Could change o rings while your at it and youll have a solid system. Otherwise you are just rolling the dice and not going to have a properly working system and wont last as long as it could.

If you dont feel like doing that then just get some 414b hotshot and charge with that, at 80% of the factory charge, its compatible with mineral and works fine.

I really dont care if people have done this with no problems, you cant argue science its still not right but some compressors are tougher then others. It could run fine for a while, then again maybe not. At a minimum it will definitely not last as long as it could and wont be as efficient either.

It's a pleasure to read professional derived advice. ;)

He could skip replacing the mineral oil and charge it with R290. ;)
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Re: R12\R134 mix.....

Postby Cburb » Mon Jul 25, 2016 7:50 pm

BC847 wrote:
Cburb wrote:R12 uses mineral oil r134 uses PAG...they are not miscible with eachother, which means they will be separated and very very little lubrication will be occurring. not to mention just very small amounts of r12 in a system will raise the head pressure higher than it should be with 134.

The 134 with mineral oil wont circulate like it should and will just migrate to low spots and sit, very hard on the compressors since the oil isnt going to be flowing with the refrigerant.

You really should recover everything, change filter drier then at least remove compressor and drain old mineral oil and add some pag, then blow the lines with nitrogen, pull into a deep micron vacuum and you should be set. Could change o rings while your at it and youll have a solid system. Otherwise you are just rolling the dice and not going to have a properly working system and wont last as long as it could.

If you dont feel like doing that then just get some 414b hotshot and charge with that, at 80% of the factory charge, its compatible with mineral and works fine.

I really dont care if people have done this with no problems, you cant argue science its still not right but some compressors are tougher then others. It could run fine for a while, then again maybe not. At a minimum it will definitely not last as long as it could and wont be as efficient either.

It's a pleasure to read professional derived advice. ;)

He could skip replacing the mineral oil and charge it with R290. ;)


Haha yea it works fine just little dangerous to some, makes people a little worried. 414b hotshot is pretty good stuff as well.
93 W250 CTD Club Cab, 5 speed: Complete 4 inch Exh. ASA/ AFE Intake, Denny t stage 2, Pump turned up, Pump timing, Injector Nozzles, #3200 Gov Spring.
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Re: R12\R134 mix.....

Postby 1STGENFARMBOY » Thu Oct 13, 2016 11:31 am

My truck will blow frost out the vent, it has a mix of 12 and 134, has for 4 years, but I guess it could be better, and it could take a dump tomorow.

when it goes I will fix it right.
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Re: R12\R134 mix.....

Postby DodgeFreak » Thu Oct 13, 2016 1:25 pm

I ended up dumping the oil out of the compressor running pag and blowing the evap and condenser out. I believe though that I have an Evap problem as its not blowing very cold. I put a new dryer and expansion valve in. Its getting cold now and I'm just going to drive it for now until I tear it apart.
92 D350 Cab and Chassis. Auto stock, wiring gremlins. 330k miles
92 W250 Ext cab rotted completely out. Auto, pump maxed, 215 ppump nozzles, Denny T2 pin.
85 D350 single wheel, converted to cummins, getrag, turned up 2 turns and afc screw flush.
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Re: R12\R134 mix.....

Postby DMan1198 » Fri Oct 14, 2016 10:39 am

Best oil to use is actually pao. It's fairly new, but is universally compatible, and non hygroscopic, so it has a lot of benefits. Absolutely any time you mix refrigerants you create an azeotrope which will always create higher pressures on both sides of the system. Azeotropes will also destroy A/C machines
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