Like others here, I've decided to take the plunge to convert my R12 A/C system to R152. I've been reading through some various threads here about it and am looking at what I'll need tool / equipment wise. I've noticed that most manifold gauge set systems available now are set up for R134. I've saw a couple listed as R12 / R134.

Since I plan on converting just the old R12 systems, can I buy a gage set with fittings for R134, and then buy adaptors to connect to my old R12 compressor, or should I look for a gage set already set up with the right connections? Or does it matter? Just looking to tap into the experience of those who have already crossed this bridge.

 

I don't think it matters how you connect, only that they fit securely...so R12 fittings to your R12 style compressor should work. In my case, I had already converted to R134 before the 152 so the adaptors were already attached when I got my (super cheap Amazon) R134 style gauge set.

As far as oil compatibility going from R12 to R152, I'm not sure. Best practice would be to drain/clean out the compressor, purge your system and get a new receiver dryer...probably telling you stuff you already know!

 

If you want a manifold gauge set that can do both r12 and r134a, I found that Yellowjacket makes one. It's been helpful to use on my RX7s and other newer cars too and seems to have a good reputation as a high quality set

Check out Yellow Jacket model 42007

If you buy this, the hoses are ready for r12 and you can attach the r134a quick disconnect fittings on the end too

 

When you retrofit, the retrofit kit should come with R134A fittings that that thread over the existing R12 fittings. This will make it easier when trying to find a current AC manifold gauge set. I converted the system in my 85 and replaced the receiver/dryer assembly and installed new green Viton o-rings. The system worked well, however the engine would hunt at idle with the AC switched on. Small price to pay I suppose.

 

Thanks for the replies so far. The manifold set hooks up to the Schrader valve connections on the back of the compressor correct? It must also connect to the refrigerant in order to transfer it from the can to the system. SA's have a Sanden, SD-508 compressor. The OD threads on the Schrader valve (where the gauge would screw onto) are a 7/16-20 thread.



I guess what I don't know is, do the later model compressors that run the R-134 have a different size / type of Schrader valve or hookup? If I got a gage set that says its for R-134, would I need an adaptor for it to fit my compressor? Are the gage sets that are advertised as R-12 / R-134 adaptable for both compressors / type fittings?

Or, is it the hookup to the refrigerant source that is different? I have a Vampire Tap for the R-152 refrigerant, it has 2 different threaded connections. The one on the right angle is the same 7/16-20 as my compressor fitting. The one that comes straight out is an odd ball thread I have not identified yet. It's not a true V thread, the crest of the threads (O.D.) have very wide lands (they appear flat) like an Acme thread form. I'm wondering if this is the style that the R-134 systems use?

If so, Then it appears I would need at least 2 adaptor fittings if I got a gauge set that is for R-134. If I get one that is compatible with R-12, then maybe I would not need any adaptor fittings?

 

Based on that compressor photo, I *think* this might be what you need for the physical connection to your SUC (blue) and DIS (red) ports





I bought this:


And it came with the addon valve that I use with the can tap, installed in the 2nd photo below, via the oddball threading you note.
The blue line goes to the suction side, red to discharge, and yellow goes between the gauge set's sight glass and the can tap.
On the gauge set, the blue and red valves open or close the gauge and the attached hose to the compressor port.



My can tap:

 

It looks like for R12 you screw the lines directly onto the Schrader valves and for R134 you have quick disconnects.

Here's a gauge set that looks like mine and has that same valve adapter for the "oddball thread", They call that part the "Brass can tap".

 

Thanks for the added info. I did a little research today and found that the Schrader fittings on the back of my R-12 compressor are what they call 1/4 Flare, the actual thread on the OD is 7/16-20. When they switched over to R-134, they changed the fittings to try and prevent someone from mixing the 2 gases. As I deduced, they went to a 1/2-16 Acme thread.

A quick search brought up several different male / female adaptors from one thread form to the other, so it shouldn't be a problem. Guess I just need to decide on a gage and buy it. After I get it it my hands, I can figure which type of adaptor(s) I need (if any) and go from there. The Vacuum pump is another unknown but I think can be treated in the same way. I've saw some pump suggestions in those other threads. Just gathering all the necessary components for this conversion is a project in itself.