How much oil to add when replacing the evaporator?

[Jason]

If replacing just the AC evaporator and accumulator, and not flushing the system, how much oil should be added before putting back the refrigerant?

The AC system was evacuated and opened to remove the evaporator box so I could add some missing foam sealing. And while the evaporator box was out I figured it was a good idea to replace the evaporator. But otherwise the system had no leaks and was working fine, which is why I'd like to avoid flushing it and messing around too much with the compressor.

[Nicholas R]

From reading through threads, I've understood the accumulator to typically hold ~3oz.

With that being said, if you're going to the trouble of replacing the accumulator and evaporator, it seems almost a shame to not flush the system.

If nothing else, once the system is vented, it's pretty easy to pull the compressor off, take out the plug, turn it upside down until all the oil drains out, then re-fill it with fresh oil. At least then you know exactly how much oil is in the system (besides the negligible amount that is lining the hoses and condenser), and you're not mixing new oil with old oil. You have to put the new oil into the compressor anyway so you might as well un-bolt it and drain it first.

[81dmc]

From reading through threads, I've understood the accumulator to typically hold ~3oz.

With that being said, if you're going to the trouble of replacing the accumulator and evaporator, it seems almost a shame to not flush the system.

If nothing else, once the system is vented, it's pretty easy to pull the compressor off, take out the plug, turn it upside down until all the oil drains out, then re-fill it with fresh oil. At least then you know exactly how much oil is in the system (besides the negligible amount that is lining the hoses and condenser), and you're not mixing new oil with old oil. You have to put the new oil into the compressor anyway so you might as well un-bolt it and drain it first.

+1

If the system is a r134a system, it would also be a good idea to replace all o rings with the new green ones if it already hasn't been done.

It's a little more work, but it's well worth it.

[DMC-81]

From reading through threads, I've understood the accumulator to typically hold ~3oz.

With that being said, if you're going to the trouble of replacing the accumulator and evaporator, it seems almost a shame to not flush the system.

If nothing else, once the system is vented, it's pretty easy to pull the compressor off, take out the plug, turn it upside down until all the oil drains out, then re-fill it with fresh oil. At least then you know exactly how much oil is in the system (besides the negligible amount that is lining the hoses and condenser), and you're not mixing new oil with old oil. You have to put the new oil into the compressor anyway so you might as well un-bolt it and drain it first.

+2 . You're already 2/3 there. Flush, replace the O-rings and service valves, replace the oil in the compressor, vacuum down and charge. Bam, you have a refurbed system. I just finished rehabbing the AC system in my DD yesterday ( new compressor, expansion valve, and drier) and did the same thing. Like Nick said, you don't have to guess what the oil charge is and you're starting fresh.