Volvo 850 still confused about total a/c oil

[cn90]

Don't overthink this issue, it is very simple.

PAG oil is ONLY needed in the compressor (as an analogy...think engine, piston, engine oil for lubrication).
Anywhere else in the system (such as evap, dryer etc.), PAG oil is a nuisance but PAG is mixed with R134a and is distributed throughout the system.

So, engineers know that during the life of the car, some PAG will be in evap, dryer etc. and they know that roughly, the compressor needs about 4 oz for itself.
If you replace ONLY the AC compressor, then most passenger cars, whether it is Zexel or Denso, uses about 4 oz for the compressor itself.

This is why most pass cars leave the showroom with 6-7 oz of PAG oil, with the main purpose of keeping about 4 oz for the compressor itself.
During servicing such as replacing individual component, let's say condenser, a specific amount of PAG is added to the condenser, not to make the condenser happy, but to make sure the compressor has about 4 oz.

Compressor can handle some abuse, when I removed the Denso compressor from my 2007 Honda Odyssey van, it leaked PAG oil and only 15oz came out. Yet it was still cooling the car (I replaced it b/c I knew I had a front seal leak).

[JimBee]

Like I said above, I thought I had a correct understanding from the Volvo tech I talked with a couple of weeks ago (at a dealership). He recommended 50 ml in the new dryer, 140 in the empty compressor.

But what got my head spinning were several things: I think Jimmy or Lee said the whole system takes about 200 ml. Yet the badge on the compressor says: "Oil 200 ml". Is that 200 into the compressor or the system. No clue is provided. Then the spec sheet came along that shows quantities to add for each component replaced. They add up to almost 400 ml for all components. That's more than 13 ounces. Then the Volvo indi today thought 140 in the compressor was way too much. Then the second generation auto a/c guy I visited today told me he puts 3 oz in a new dryer and 3 oz in a new compressor (so now we're back to ~6 oz + what's in the other components).

So while we still lack an ultimate authoritative last word on this from industry engineers (I did email Valeo who bought the Zexel brand from Bosch, got no response), the consensus seems to be how you (cn90) summarize it above—the spec sheet notwithstanding.

My apologies for doing some second guessing here. I just don't want to toast another compressor. At highway speeds that could cause a mess.

So hoping for a good outcome.

[jimmy57]

i have worked on loads of automotive a/c in many makes over the years. This oil quantity topic rattles a lot of people. I have not read the Volvo manual for an 850 in a while to see what the test around the oil chart says.

The leak rate always gives a question mark. How much blew out?

If there is doubt do more rather than less. BUT keep in mind the new fill amount. Most new fill amounts for single system is 7-9 oz. If it is a vehicle with a rear then 4-6 oz more.

I have repaired low cooling issues after previous repairs by dumping out oil. Back when there was a sight glass you could see clear-amber-clear- amber as the oil would puddle and then move through system. The pressure gauges would fluctuate in concert with the more viscous oil slowing flow through TXV or orifice tube. I had a 960 that would jolt the whole car 6 seconds after engine start after overnight rest due to oil puddling only after the compressor and accumulator was changed. The tech put compressor on with full oil load then put in 4 ounces in accumulator. There was no flushing so the evaporator and condenser each had around 1.5 ounces.
P2 has compressor run during starter motor cranking to clear liquid to prevent this even with correct oil and refrigerant amounts..

[cn90]

JimBee,

My guess on the "200mL" label is that: on the factory floor for a dry fill, all the assembly line worker needs to know is: add 200 mL.

[abscate]

Jim - remember the compressor manufacturer has no clue about what AC system the compressor is being used with - so how can they really make a recommendation on system fill. Does that help?

[JimBee]

UPDATE, Edit:
What made the most sense to me was the suggestion of the indie a/c shop guy who has been in business for 40 years. With the compressor known to be empty, as mine were, and new dryers, I put about 90 ml in each component in the 96 855 that I mostly drove through the summer and, functionally, it seems fine.
Unfortunately, the dryer's large hose coupling does have a small leak that I'm monitoring. That car is stored until spring. If it needs a recharge, I might redo that coupling. Otherwise, it seems good. Keeping fingers crossed on the evaporator.

Looking back at my notes, I see that the other 96 855 got 50 ml of PAG oil in the dryer and 140 in the replacement compressor, based on a dealer's tech suggestion. Though that car has been driven very little, the a/c system seems to be working fine.

[abscate]

My recent Valeo sticker said 180cc, alldata says 70 cc if the system has not been blown open. Taking the average was 125cc, which is exactly how much I had in PAG 46. I put 62.5 cc into each port and shook it for 3 minutes by inversion