Not to hijack this thread, but I’ve got a similar question. I’m replacing the old r12 compressor with a new Denso unit, and the FSM says to remove oil from the new compressor: 80ml - (ml removed from old compressor).
Almost no oil came out of the old compressor - like one drop. That would indicate that I should drain almost all of the oil (80ml) from the new compressor, minus 10ml for the accumulator I’m replacing as well. Is this common with NSXs? I just don’t want to drain all the oil and fry the new compressor.
For what it’s worth there’s not a big leak in the system - the refrigerant leak is the o-ring between the evaporator and one of the lines. The condensers are intact and not leaking.
As you stayed with the R12 compressor, don't know the current system configuration described below and the reason for replacing the compressor.
You are using R12 compressor because;
1. you stayed with the R12 refrigerant and thus using mineral oil ND-OIL6.
2. the system was retrofitted to R134a with ND-OIL8 (PAG) and kept using the R12 compressor.
3. using alternative refrigerant such as RS24 with mineral/synthetic oil and kept using the R12 compressor.
You are replacing the compressor to the new Denso one prefilled with the total system amount of;
a) mineral oil (R12)
b) ND-OIL8 (R134a)
First, the information in the original workshop manual is wrong.
The information you have (80cc - wrong) is for the R12 mineral oil and that is the wrong info.
Should have been 120 - 130cc of R12 mineral oil instead.
For your reference, for the R134a ND-OIL8 (PAG), the total system amount is 160cc - 180cc max.
You should not drain more than 50cc from the new compressor but, and this is a big but.
Because you lost so much refrigerant that the oil couldn't return back to the compressor, you just don't know how much oil is left in the system or even what type of oil.
Fair amount of oil could have leaked to the outside world if the refrigerant was leaking.
You stated that
'For what it’s worth there’s not a big leak in the system' - and this is the problem.
Even when the car is parked, the system is under pressure that you are losing the oil all the time.
Please remember that the compressor oil travels all around the system by bonding/mixing with the refrigerant.
Thus, the 'guessing work' as mentioned in my post.
You may have certain amount of oil left inside the system and it could be combination of mineral, PAG, POA oil depending on what was done in the past.
On top of these, you don't know how much contamination you have inside the system.
Because you only saw one drop of oil out of the compressor, you may have burnt oil left in the system, contaminated with the moisture, oxidised, etc.
If the refrigerant leaked in the past, don't know the full a/c service history and getting new compressor, don't bother with the oil balancing.
Just have your system flushed.
Many compressor manufacture won't warranty your new compressor unless required processes were followed.
This will also include but not limited to replacing the drier/receiver and the exp. valve at the same time.
Kaz