Can Someone Explain A/C Oil

[adamsanders]

Can someone please explain the A/C oil situation. A lot of resources I have read so far make it seem over complicated and not very clear. I’m trying to retrofit my R12 system in my 91 F250 to run R134A. I planned on replacing my accumulator and orifice tube, pulling a vacuum, and then charging. I had also contemplated taking my compressor out and draining the old oil out and blowing out the lines with compressed air. Is that a good idea? What about o-rings?

Finally, what about the oil? Is there a fill port on the compressor or do you put it in with the manifold gauge set? With the system pull enough vacuum to pull a liquid oil into the system? How do you know it will go where it’s supposed to?

Thanks

 

[Booyah45828]

Old R12 systems used mineral oil to lube the system. Mineral oil isn't a compatible lubricant with R134a.

So you should clean the old oil from the whole system using a flush of some sort. Drain as much of the old oil from the compressor that you can, and then add the correct oil and amount to the system. I recommend replacing all of the o-rings and seals to ones that are r134a compatible. If you bought a retrofit kit, the o-rings and oil should be included.

It's fine if there is a little of the old oil left in the system, you just don't want the entire volume left in there, so remove as much of it as you can.

I typically put half the system oil volume in the compressor, and the other half into the accumulator. You have the system apart, pour the oil into the ports where the lines go. A vacuum on the system will pull oil if you need it to, but you should already have the oil in the system prior to putting it together and pulling the vacuum.

The only time I add oil to a system by vacuum is if I need to add UV dye to a leaking system.

The only thing in the system that needs lubricated is the compressor. With the system running, the oil will be circulating with the refrigerant throughout the whole system. As long as the compressor isn't dry or slugged with oil, you need not worry about it being lubed, as long as the correct type and amount of oil is in there.

 

[adamsanders]

So when you say “flush” the system how do I go about doing that? Would the system have to be running to do that? I assume there are products that claim to do that. Or just blow compressed air through it?

 

[Booyah45828]

Google ac system flush. You essentially blow the liquid through the condenser, evaporator, and hoses.You should have the system apart or at least disconnected at certain points to do it. Doing a flush removes old oils, acids, and other contaminants that might be in there. Most parts stores will have some sort of ac flush solvent on the shelf. Most oem's recommend only using that, so don't use brake cleaner, carb cleaner, gasoline, etc.

They make commercial tools that do it, here is an example https://www.amazon.com/FJC-2710-System-Flush-Kit/dp/B0002JMEQW , but you can get by without it by using an air nozzle.

You'll have to use flush to clean the oil, it's too thick to simply blow out with air.

 

[Kizer]

So when you say “flush” the system how do I go about doing that?

I "rented" the tools from the parts store (O'Reilly's).

 

[franklin2]

Old R12 systems used mineral oil to lube the system. Mineral oil isn't a compatible lubricant with R134a.

There is more than one oil used with r134a. Ester oil, used in conversion kits that you buy, is compatible with the old r12 mineral oil. PAG oil is not.

So get the old r12 gas out of your system, do not flush anything, do not pour anything out. Don't change any o-rings unless they are leaking. If the compressor spins free and seems ok, don't mess with it, don't pour any oil out. Follow the instruction on the retro fit kit and put the new retro fit gas/oil mix into the system after you pull a vacuum on the system. Done.

Can't get much simpler than that.

 

[adamsanders]

How would I know how much oil is in the system currently though?

 

[riphip]

Check here: https://www.techchoiceparts.com/refrigerant-and-oil-capacities/ford-light-truck

 

[franklin2]

How would I know how much oil is in the system currently though?

Why does it matter? The old oil just lays in the system, it does not mix with the 134a. The new ester oil in the conversion kits mixes with, and circulates around with the new 134a refrigerant.

 

[Booyah45828]

There is more than one oil used with r134a. Ester oil, used in conversion kits that you buy, is compatible with the old r12 mineral oil. PAG oil is not.

So get the old r12 gas out of your system, do not flush anything, do not pour anything out. Don't change any o-rings unless they are leaking. If the compressor spins free and seems ok, don't mess with it, don't pour any oil out. Follow the instruction on the retro fit kit and put the new retro fit gas/oil mix into the system after you pull a vacuum on the system. Done.

Can't get much simpler than that.

I know of the different oils and whats compatible.

I'd rather not have the old oil taking up space in the system. Causes a decrease in ac performance and most retrofits typically need all the help they can get.

A flush on an unknown system can reveal why it wasn't working in the first place.
His system likely has a leak, which is why he's looking to retrofit it, good chance it's one of the o-rings or compressor seals. I've never heard anybody retrofitting a working system. Usually it's after it's sat dormant and unused for several years and then an owner change.

To each their own.
You do you, I'll do me chief

 

[Booyah45828]

How would I know how much oil is in the system currently though?

It doesn't matter how much is in it. You're getting rid of it so get as much out as you can.

The only time the amount of oil removed is important is if you're replacing a single component in the system and need to keep the total volume the same. Then you'll measure the oil removed from what you're replacing, and add the same amount of oil into the new component.

 

[Clb]

@franklin2
How do you explain the conversion, green o rings and seals in the conversion kit if nothing (edit but ester oil) is required for a 134 gas change?

Asking cuz I am doing this on the crawler soon...

 

[Jay_d]

I just poured flush into the lines with everthing unhooked and blew it out with air hose. Also did the evap core. Id put a new compressor, expansion valve and dryer if i was that deep in, probably a new low side psi switch too.

The retrofit fittings are trash and will either leak ftom being loose, or break from being tight enough. Be wary

 

[chris142]

Non chlorinated brackcleaner is a great flush solvent. You want 3.5oz of oil per pound of R134a. Then add 1 more oz of oil. It does not matter where you put the oil as it will get moved around as soon as refrigerant is added.

Better to slightly over oil than under oil. Too much oil will effect cooling but it has to be a lot extra. Make sure to use the orange orifice tube and adjust your cycle switch to shut off @20 psi.

 

[franklin2]

@franklin2
How do you explain the conversion, green o rings and seals in the conversion kit if nothing (edit but ester oil) is required for a 134 gas change?

Asking cuz I am doing this on the crawler soon...

Because the green o-rings are compatible with the r134a. But wait. Guess what they figured out from real world experimentation. The old r12/oil mix "pickles" the o-rings and the r12 hoses. If they have been exposed for a long time to the r12/mineral, they will hold up to the r134a.

If you ever change the o-rings or the hoses with new ones, you must use r134a compatible components.