DIY: R-12 to R-134a Conversion (How To)

turbogate

Life is Boost
Authorized Seller
Contributor
Joined
May 18, 2005
Messages
424
Likes
0
Location
South, FL
Just checking on this again, I'm abotu to redo my system. I'm going 2jz which has a r134a compressor. Is it possible to still use r12?

Another important question, where can I still get the paralell flow condensor? I've gotten a few part numbers looking stuff up, one being 1039293 from american condensor. Is this right?
Great thread! Can anyone confirm this part number above or if anyone recently got a parallel flow condenser, can you share which brand/model condenser you got? Thanks all.
 

Doat

New Member
Authorized Seller
Joined
Feb 6, 2012
Messages
2,599
Likes
0
Location
Houston, TX
I bought mine from Carpartswholesale.com part number P39293P. I recently replaced my condenser, compressor, dryer, and expansion valve following this guide for the most part and now my AC blows ice cold. You might have to bend a bracket that holds one of the suction tubes to make it fit but that's about it.
 

turbogate

Life is Boost
Authorized Seller
Contributor
Joined
May 18, 2005
Messages
424
Likes
0
Location
South, FL
I bought mine from Carpartswholesale.com part number P39293P. I recently replaced my condenser, compressor, dryer, and expansion valve following this guide for the most part and now my AC blows ice cold. You might have to bend a bracket that holds one of the suction tubes to make it fit but that's about it.
Thanks for the info. Was it recent? I guess they are discontinued, they don't have it in the link provided and other places which pop-up with that part #
 

supranaut

Rock'n Death with Spikes
Authorized Seller
Joined
Apr 5, 2005
Messages
99
Likes
1
Location
STL
How different are the 89+ condensers? The ones ive found show only for 86/87 model years...
 

SupraClaou

Member
Authorized Seller
Contributor
Joined
Sep 1, 2006
Messages
840
Likes
0
Location
Athens,Greece
Can somebody help me on that :
I have a 2JZ swap. The 2JZ already has an R134 compressor on..., so the car's A/C system is left with only one charging port which is located on the hard line that is located on the right side of the condenser , since the other port was originally on the 7M compressor which is no longer on the car! What's the deal now with only one charging port??

Last , on a MA70 7M Supra mk3 ,which charging port is the Low pressure and which the High pressure ???
 

jetjock

creepy-ass cracka
Authorized Seller
Contributor
Joined
Jul 11, 2005
Messages
9,439
Likes
1
Location
Redacted per Title 18 USC Section 798
According to the TSRM and Cygnusx1 the LOW pressure port is located on the 7M compressor manifold isn't it? And the HIGH pressure port is on the hard line near the dryer/condenser...
Yes. The compressor manifold has two lines. One is suction and the other is discharge. The low pressure port is on the suction line.
 

Nick M

Established 1994
Authorized Seller
Contributor
Joined
Sep 9, 2005
Messages
8,810
Likes
8
Location
U.S.
The low pressure port can only be between the pressure drop and compressor. On any car. Some are convenient, like with an orifice tube, which we don't have.
 

Asterix

Lurker of Power
Authorized Seller
Joined
Mar 31, 2005
Messages
441
Likes
2
Location
Vienna, VA
(Back from the dead on Halloween!)

I'm collecting all the bits and bobs to get my A/C running again after so very long and I'm rather annoyed by the lack of definitive information about conversions from R-12 to R-134a. I'm not interested in turning into an ice cube, but I do want the system to last, be reliable, not leak, and do a good job of cooling/defogging during the cooler months in northern Virginia.

Perhaps someone who knows can address my concerns!

I bought a new Denso compressor, and it is labeled that it has ND-6 oil inside already, which is for R-12. Yes, I understand it's OEM spec, but R-12 has been super expensive and obsolete for over two decades now. I also bought a new receiver/dryer from Toyota and now I'm worried that the drying material inside is not R-134a compatible, again because "OEM spec for a 1988 car". Poo to that. To continue, I got a new expansion valve for my vehicle according to Rock Auto, so again I'm seriously concerned it's not right for R-134a.

From the linked Toyota TSB, I need to check and see if I have the replacement dryer or not. At least that question is answered.

The new condenser I bought (also directly from Toyota as nobody else has them) is serpentine, but there are 2 paths between ports. Is this considered "parallel flow"?

The peeps at Sanden have a guide about changing to R-134a (https://www.sanden.com/objects/retro.pdf) that includes a warning that changing the refrigerant will result in greater wear. I'm guessing their comment about discharge pressuring being 10-15% higher is the cause of the extra wear. Changing the refrigerant results in higher high-side pressure doesn't make sense to me. But, I'm an engineer, not a chemist. Still, 15% doesn't seem like enough for me to worry about.

I'm up for changing all the seals and o-rings anyway, so that's not a concern. All of mine are ancient, and definitely worth changing.

At least the two hoses to the compressor I bought claim they are compatible with both R-12 and R-134a. Kudos to Four Seasons! Toyota has discontinued one of them, so Four Seasons is the place to go anyway.

So, the compressor is full of ND-6 oil for R-12. The original post of this thread just talks about draining as much as I can, then putting in PAG oil for R-134a. Well, what about what's left? Thanks to the linked TSB I know the answer to this! Don't worry about what's left. However, the sight glass in the receiver will be worthless. I can live with that.
 

JDMMA70

Active Member
Authorized Seller
Joined
Dec 4, 2006
Messages
2,645
Likes
12
Location
Houston
(Back from the dead on Halloween!)

Luckily I'm alive and well eh?

The new Denso compressors are compatible with R12 and R134a and have been R134a spec'd since the mid 90's. The Oil inside is most likely ND-6, all you have to do is drain the old oil out by turning the compressor over and turning the clutch a few revolutions. About 60-80mL of oil is in the compressor from factory in most cases, sometimes more. Once drained you can add either ND-8 (Pag 46) or Ester #100. The amount you add is dependent on what parts you replace.

The Denso driers, and TXV are all R134a spec, but compatible with R12 as well. The barrier hoses are different for R134a but to be fair as long as R134a oil is used even the old R12 barrier hose will be just fine.

Also your sight glass will be fine, they just wanted techs to black it out so it wouldn't be used to judge a vehicles charge. You can leave it be since it still aids in diagnosing certain A/C issues by being able to see the refrigerant flow.

As far as wear is concerned, increased wear was an issue when the gas was initially introduced, that was over 20years ago and improvements have been made on both the mechanical hardware and fluid side of things. Its true it runs at a slightly higher pressure than R12 but as long as your system conversion is done properly, you should be problem free for many years.

To make charging easy as my guide states, just charge 24oz or two 12oz cans into the system when you get around to charging if you are doing it yourself.

Hope that helps, let me know if you have any other questions.

P.S. its going to be very cold so don't worry.
 
Last edited:

Asterix

Lurker of Power
Authorized Seller
Joined
Mar 31, 2005
Messages
441
Likes
2
Location
Vienna, VA
Thanks for the info, JDMMA70! I feel better about it all now. I want to do this right, not just so it works.

The Denso compressor definitely has ND-6 in it from the factory. I worry about putting incompatible lubricants together, but apparently it's not a problem.

I'm probably going to buy a 30lb jug of R-134a so I have enough for the rest of my life (and my second car). It looks like it's going to be phased out in a few years, so I want to avoid not being able to get it.
 

3p141592654

90T
Authorized Seller
Contributor
Joined
Oct 11, 2005
Messages
4,008
Likes
43
Location
Thousand Oaks, CA
The old oil is not miscible in R134a. So any remaining residue will have no ill effect, it will just sit as a blob somewhere in the system.
 

JDMMA70

Active Member
Authorized Seller
Joined
Dec 4, 2006
Messages
2,645
Likes
12
Location
Houston
Yes the condenser were different. They changed in September 1987 which is the same for all MK3s going forward. Looks like the condenser was discontinued. Hopefully Denso starts manufacturing them again.
 
Last edited:

plaaya69

87T Supra
Authorized Seller
Contributor
Joined
Nov 18, 2006
Messages
1,282
Likes
51
Location
Lake County, IL