Whole A/C system Oil Capacity from R12 to R134A

[ConixC]

Just like the title of the thread says I'm trying to figure out what the whole A/C system oil capacity. I'm completely rebuilding my ac system only the dryer and evaporator remain in the truck and its been that way for the past 20+ years so I ordered all new parts and I don't know how much oil to add after I rebuild the system. I have read different capacity's in a couple places one says 8 and another says 10 ounces and I don't want to over or under fill the system.

 

[fast 99]

Use same amount of oil going from R12 to 134. Using a little more oil is much better than not enough. I have never seen a trashed compressor from excessive oil. Nearly every seized or noisy compressor is dry. Excessive oil can reduce cooling but 2oz won't be noticeable, takes much more than that. Be sure and reduce refrigerant volume from R12 specs.

 

[ConixC]

Do you know what the amount of oil used in the stock system was? That's the main problem I'm having is locating that information.

Use same amount of oil going from R12 to 134. Using a little more oil is much better than not enough. I have never seen a trashed compressor from excessive oil. Nearly every seized or noisy compressor is dry. Excessive oil can reduce cooling but 2oz won't be noticeable, takes much more than that. Be sure and reduce refrigerant volume from R12 specs.

 

[fast 99]

10oz sounds about right, don't have access to Mitchell right now, may be some can provide that information. Originally should have been a sticker on drier top. New compressor might have that information in the box.

 

[Bextreme04]

Do you know what the amount of oil used in the stock system was? That's the main problem I'm having is locating that information.

It depends entirely on what compressor you have. If you have the big A6 compressor it take significantly more oil because the compressor has a large reservoir at the bottom that you fill separately. Generally speaking, you should add some to every new component and then make up the difference to final capacity through the charge port while charging the system. I would put at least 1.5 ounces in the return side of the compressor, inlet side of the condenser, inlet side of the evaporator, and 1 ounce in the filter/dryer.

A new(or rebuilt) A6 compressor gets 10.5oz of PAG 150 and then sends that throughout the system. Subtract whatever you added to each component from 10.5 and then add the rest into the reservoir of the A6 compressor on the bench before you install it. An R4 equipped vehicle would take ~8oz of the same PAG 150, but the compressor doesn't have a reservoir to fill. Just add the amount to each component and then put the remaining amount in when you fill it through the charge port.

 

[Bextreme04]

Do you know what the amount of oil used in the stock system was? That's the main problem I'm having is locating that information.

I would also recommend updating the stock orifice tube to a blue one when changing out to R134. It gives it almost stock R12 performance. I have an A6 compressor and blue orifice tube with the O.E. condenser and evaporator and it works awesome. ~50-55 degree upper vent temps with 100 degree outside air temp stationary at idle. Gets even colder while moving. Would be even better with a newer parallel flow condenser.

 

[ConixC]

The A/C Compressor I have is the pancakes style I believe. Here's a picture of the the one that came with the truck. I have it had mocked in place to make sure I ordered the right one.

 

[RustyPile]

The A/C Compressor I have is the pancakes style I believe. Here's a picture of the the one that came with the truck. I have it had mocked in place to make sure I ordered the right one.

That's an R-4 compressor - no reservoir... Unless you're going for the "stock look", that's the last choice in compressors.. An A/C system doesn't know which compressor is installed in the system.. All A/C compressors work the same way, they all pump freon while it's in a gaseous state... The big A-6 compressor doesn't lend itself very well to cycling off and on. A Sanden or similar would be a better choice. Vintage Air and other automotive A/C manufacturers offer a line of replacement compressors along with proper mounting hardware.