[mike69]

Guys,

I'm currently looking to get my 70 GTO A/C working. It has worked until a couple years ago when I pulled the motor to rebuild it. It was previously R12 and I am trying to decide on whether to go back to R12 or switch to R134a. I have some R12 I have purchased over the years so that's not an issue. I was prepared to switch to the R134a so I drained the R12 oil from the compressor and flushed it several times with R134a compatible ester oil. Now I'm having second thoughts about the switch to the R134a.

Here's my questions:
Can I use the Ester oil I flushed the compressor with if I stick with R12? If not what is the currently available R12 compatible oil.

I purchased a manifold gauge set online (waiting for it to be delivered). But I believe it is set up to work with R134a fittings. I know there are R12 to R134a fittings conversions, but are there also conversion kits to allow me to use these new gauges with R12 fittings? I realize I could use the R134a adapter fittings and just fill the A/C with R12 anyway, but I prefer not to convert the fittings if I'm still using the R12. thanks for your input.

Mike

 

[johnsongrass1]

I am not an expert but in my experiences the 134 likes higher operating pressures so it tends to work better in systems designed for it.
If it were me, Id use the 12. 134 in a 12 system never seemed to cool as well as 12 in 12 system.
Adaptors aren't much. probably a good thing to have around anyway. Especially if your inclined to mess with AC systems in general.

 

[mike69]

Does anyone know what size the traditional R12 couplers are? If I can find that out I can order generic couplers so I can charge through R12 fittings. Is there a specific size of those R12 fittings? I've searched online and I can't find it.

 

[curtis73]

There are R12-R134 adapters that screw on your old tubes.

Even though you flushed the compressor, there is still a ton of mineral oil not only in the compressor, but throughout the whole system. You'll never get it out. From what I understand, PAG oil with R12 will turn the whole system into a frothy mess and kill the compressor, but I've never really looked into it.

Your compressor won't work well with 134, and the expansion valve needs to be replaced. R134 needs a higher pressure delta than R12. If you just charge it with R134 you might get a little bit of cooling, or no cooling. I have done a couple with just filling it with R134 on an older system, and it makes some semi-cool air.

The way to do it right is to replace every single piece. Start fresh with new lube, and get components that work with R134.

The short story is, you have to use the oil that goes with the refrigerant because it is miscible (soluble) in that refrigerant only.

 

[mike69]

I pretty much decided that I'm going to stick with the R12. The only issue I have is the new manifold gauges I ordered I believe have R134a valve compatible quick release couplers. Does anyone know what the size is for the old R12 valves so I can order the couplers?

Mike

 

[mike69]

I think I answered my own question. I looked up a youtube video and it shows that there are no quick connect couplers for R12 systems. The AC manifold hoses screw to the high and low ports on the AC. I guess my next question is how do you keep all the refrigerant in when your attempting to unscrew the hose from the connector?

 

[Eduramac]

I think I answered my own question. I looked up a youtube video and it shows that there are no quick connect couplers for R12 systems. The AC manifold hoses screw to the high and low ports on the AC. I guess my next question is how do you keep all the refrigerant in when your attempting to unscrew the hose from the connector?

You Never flush a compressor. That is never done and you don't flush the system with oil. You flush it with ac flush. And you add the appropriate amount of the correct oil to the components you flushed evaporator the condenser etc. There are charts that tell you how much to add while recharging the system. Now you lost all of the correct oil from the compressor flushing it. You need someone that knows what they are doing to correct what you did.

 

[Phillip Nickles]

I think I answered my own question. I looked up a youtube video and it shows that there are no quick connect couplers for R12 systems. The AC manifold hoses screw to the high and low ports on the AC. I guess my next question is how do you keep all the refrigerant in when your attempting to unscrew the hose from the connector?

In the old days we used a shut off valve on the high side manifold hose. Eliminated a big burst of refrigerant when taking off the high side manifold hose, a/c off. The low side is disconnected with the engine a/c running, only about 30 lbs then, just a little pfft.
Check, R-12 hoses are probably still available.
With older system they don’t do well with R-134. The older systems are too large IMO. Even with a proper condenser and 134 compatible compressor (Sanden) and 134 expansion valve the problem I ran into was the evaporator was too large to work properly. 134 runs higher head pressure so the system can’t be filled to the capacity it was designed for, the reason for cool not cold air. I would unwrap the tape to partially expose the capillary tube from the expansion valve where it attaches to the outlet tube of the evaporator tube and this would partially flood the evaporator achieving a decent amount to boil off. The POA would also need to be recalibrated for a lower pressure.
There was a refrigerant marketed awhile I believe was called freeze 12 that was 134 mixed with butane or something of that sort. It would mimic 12 pressures and cooling, but I haven’t seen freeze 12 in years. A safety concern with a flammable additive I’m sure.
I don’t know what shape your system is in but back in the day we saw hoses, shaft seals and compressor cases leak on cars that were only 5-10 years old.
I think 134 works best in systems designed for it.

 

[Ford blue blood]

Let's not forget the hoses. 134 needs barrier hoses, the old 12 hoses will leak or perhaps even rupture under the higher pressure of the 134.