Question about oil in new system

[65NovaAC]

I have a 1965 Chevy Nova and am putting together an AC system for it. I am using a factory under dash evaporator that I have cleaned up and changed the TXV to work with r134a. I also had it retrofitted with o-ring fittings. The engine is a 2006 5.3 Ls engine with a brand new Denso 10S20 compressor. The rest of the system is brand new modern components.

My question is about PAG oil. I looked the oil capacity of the system up in several places and it was listed at 7.1oz. I added this to the low port of the compressor and it seems like way too much at first glance. When I rotate the clutch, oil shoots out of the high pressure side. Did I misunderstand something and add too much? Any help or advice would be greatly appreciated. Thanks in advance!

[Cusser]

I looked the oil capacity of the system up in several places and it was listed at 7.1oz. I added this to the low port of the compressor and it seems like way too much at first glance. When I rotate the clutch, oil shoots out of the high pressure side.

Disclaimer: I'm NOT an AC professional. That said, I do have some AC experience.

So - like OJ - I'd like to take a stab at this. Except when I've had to flush out a new compressor that came filled with PAG and I needed 525 mineral-type oil for R-12, I have not rotated the compressor drive plate until the low and high side fittings have been installed; I'd EXPECT and HOPE that oil would come out the high pressure side, the compressor is a pump. Yes, I would rotate the compressor (once installed) at least 10 revolutions by hand before evacuating and charging the system.

Remember - UV dye is fine, NEVER ADD ANY SEALERS OR REFRIGERANT CONTAINING SEALER.

[JohnHere]

My question is about PAG oil. I looked the oil capacity of the system up in several places and it was listed at 7.1oz. I added this to the low port of the compressor and it seems like way too much at first glance. When I rotate the clutch, oil shoots out of the high pressure side. Did I misunderstand something and add too much?

Maybe. It appears that the OEM A/C compressor for the 1965 Nova was a Frigidaire/GM A-6, which had a sump to contain the original 525 mineral oil. The specification that you found for the total amount of mineral oil might or might not be the same for the modern Denso compressor, which doesn't have a sump. In the Denso literature, I would look up the exact model number of your compressor that's listed on the data plate to determine how much oil and what viscosity the manufacturer recommends. Note that 10S20 is a compressor series, not the specific model.

Based on the Denso specs for the total oil amount, I would distribute it as follows: 1-1/2 fluid ounces in the condenser, 1 ounce in the evaporator, 1/2 ounce in the receiver/dryer, and the rest in the compressor.

As pointed out earlier, the compressor is a pump. So if you rotate the main-shaft by hand after putting the oil into the low-side port, it will just eject it from the high-side port. What you want to do is distribute the oil throughout the system as mentioned, assemble everything, then rotate the main-shaft by hand 10 or 12 times to ensure the compressor doesn't "slug" on initial system start-up.

What mechanism(s) are you using to prevent the evaporator from icing-up?

[65NovaAC]

The only part of the system that is original is the evaporator. Everything else is modern and new

[JohnHere]

The only part of the system that is original is the evaporator. Everything else is modern and new

Yes, I understood that from your original post. What I'm suggesting is that maybe the 7.1-ounce oil specification that you found elsewhere was the spec for an original A-6 used in a factory A/C system installed in a '65 Nova, not your car with its mostly non-OEM, modern, and new system. I can't say for sure. I would go by whatever Denso says is the correct oil amount and viscosity (usually ND-8 or PAG-46) for your new compressor and put that in, distributing the oil among the various new components and the OEM evaporator as mentioned earlier.

[65NovaAC]

Ah ok gotcha. The 7.1 oz spec is for a 2006 Silverado which was the donor vehicle for the compressor. Thanks

[Tim]

What I'm suggesting is that maybe the 7.1-ounce oil specification that you found elsewhere was the spec for an original A-6

Just for reference, any OE style A6, single-unit system. Will take 11 ounces of oil.

[JohnHere]

Just for reference, any OE style A6, single-unit system. Will take 11 ounces of oil.

Thanks. I thought 7.1 ounces seemed "light" for an A-6.

The 7.1 oz spec is for a 2006 Silverado which was the donor vehicle for the compressor.

Ahhh...now that we have clarification about where the compressor came from, yes, my references say that 7.1 ounces of PAG-46 is the correct amount for an '06 Silverado.

If you haven't already done so, solvent-flush the OEM evaporator to remove all the old mineral oil. Then distribute the PAG-46 as discussed previously and assemble the system, preparing it for evacuation and charging.

[DetroitAC]

The oil qty is determined for a complete system, not a compressor only. Oil qty is also very conservative, the factory amount is usually more than necessary. There is nothing wrong with 7.1 oz, sounds just fine, it's a random shot in the dark, but I suppose a front only car is ballpark the same size as a pickup.
I have no idea how you are calculating precise amounts to put into each component. In my world nothing is that well defined, a new car on the assembly line has 100% in the compressor, very first engagement has an unique cycling routine to pump it out slowly. IMHO as long as you aren't putting 100% in the suction port, things will be just fine, I personally wouldn't open known good connections to add oil, but there are lots of ways to skin a cat.

Good luck with your LS swap

[JohnHere]

The oil qty is determined for a complete system, not a compressor only. Oil qty is also very conservative, the factory amount is usually more than necessary.

Yes, I know. But we should keep in mind that this is a custom system composed of parts from a '65 Nova (OEM evaporator), an '06 Silverado (OEM Denso compressor), and possibly other new aftermarket parts, although the OP didn't specifically say. So the oil specification for this custom system will most likely vary from a '65 Nova factory system and an '06 Silverado factory system. However, I'm leaning toward the Silverado oil specification as being more in line for this custom R-134a system using the aforementioned components. In any case, it's somewhat of a guess, I think.

There is nothing wrong with 7.1 oz, sounds just fine, it's a random shot in the dark, but I suppose a front only car is ballpark the same size as a pickup.

If a '65 Nova factory A/C system with an A-6 takes roughly 11 ounces of oil and the '06 Silverado specs call for 7.1 ounces, it seems as though the latter amount is at least in range for the OP's custom system. So, yes, I agree with you.

I have no idea how you are calculating precise amounts to put into each component. In my world nothing is that well defined, a new car on the assembly line has 100% in the compressor, very first engagement has an unique cycling routine to pump it out slowly. IMHO as long as you aren't putting 100% in the suction port, things will be just fine, I personally wouldn't open known good connections to add oil, but there are lots of ways to skin a cat.

Let's just say that 7 ounces is the oil "sweet spot" for this particular custom system as deduced above. As I recall, the OP inferred that he had a hard time getting much oil in the compressor when he had it on the bench, let alone all 7.1 ounces, although I don't recall his mentioning exactly how much. So, let's presume he was able to pour in about 4 ounces, a relatively small amount, with approximately 3 ounces yet to be put in...somewhere...leaving us with the evaporator, condenser, R/D, and lines/hoses as possible additional oil receptors.

The amounts I mentioned distributing into the components aren't absolute by any means, just a suggestion. So if one wanted to distribute, say, 1 ounce to the evaporator, 1/2 ounce to the condenser, 1/2 ounce to the R/D, and 1/2 ounce to each hose--or any other combination to make up the approximate 3-ounce compressor shortfall--seems fine to me.

In summation, I think we agree that we still need about 7 ounces of oil, in total, in this system for the compressor to stay "healthy." If the compressor will take only about 4 ounces maximum (or whatever amount it will take), then the rest will have to be distributed elsewhere regardless of what the manufacturers do on the assembly line.

Not disputing...just discussing for consideration.