conversion from R12 to R134

I'm doing a conversion from R12 to R134 on a 1982 Vette.
I replaced the compressor ( new AC Delco), seals, hose assembly, and dryer.
I had the condensor checked for leaks, resealed the heater box, installed a new heater core, checked and or repaired all vacuum lines, checked all actuators for operation, including the right vent door.
I plan to evacuate the system for one hour, then see if it holds vacuum for one more hour.
My question is - What amount of oil do I put in the system ( I have Estercool oil and some Pag oil )and how many pounds of R134?
I'm just an old wrench wanting to finish a five year project. Thankx,
xfire

The rule of thumb is 2 oz per hose, 3 oz for the accumulator/dryer, 3 or 4 oz for an evaporator or condenser, depending on size.

This does vary. Partly depending on how thoroughly the system was cleaned out already. New parts are completely clean, but sometimes come with some oil. Which ones were yours?
The compressors vary a great deal. Check the mfg specs. The information that came with the compressor will usually tell you.

I know this is general stuff, but it's a starting point.

Thanks for the help Ken, I think I have the oil part figured out now, but, when I put the R134 in, do I look for the same Hi Side / Lo side readings on my gauges same as if it had R12 in the system, or, do you put in so many pounds? One kit I saw said to only put in 85% of what the system is to have in it.
The older I get, the less I know!!!


Thanks,
Denny

85% is a good starting point. Then check the performance and pressure of the system. You may or may not need a bit more.

Low side pressure will be about the same. The high side pressure could easily be 10% greater.

And with the original expansion valve, you will have about 10% less efficency. But in the small cabin of the C3, you won't notice the difference.

Thanks again Ken, for your help. I'll let you know how it turns out.
I still have lots to do on the thing, I rebuilt the motor and about everything else inside, under, over, and on top!

Denny

I'm thinking of doing a conversion on my 79. Was it expensive ? and do you really have to replace all the parts. My R12 system works but with the future demise of it....

The answer is both yes and no.  None of the rubber parts or seals in our cars are designed to hold the R134a.  But through age and time a coating forms on the inside of the system, which provides a barrier seal.  If you don't flush the system, it will usually hold.  But a leak will require updated components anywhere it needs to disturb the coating.

I'm not sure yet, I just got the motor in and started. I still have to put the A/C pump and smog junk on yet. I'll let you know how it works when I'm done.

I replaced everything, including the "o" rings for R134.

xfire

Jim, if your system is working well the answer is no, it's not worth it.

But if you need to do repairs, then yes it is worth it.  R-12 is going away.  Sooner or later we will all need to convert.