TheSamba.com :: View topic - How much oil (and where) in AC compressor

Thu Jun 13, 2013 9:01 am

After all the reading I've done, including the math on the Sanden SD-508 manual, I still don't feel confident about how much mineral oil to add back into the drained compressor and where. I have drained it, put new oil in/through, and drained again. Then I put 4 oz. into the plug hole. This is here I get stuck. Do I add more mineral oil to the H/L orifices? How much? This compressor is from my '84.

Hans

Thu Jun 13, 2013 11:11 am

In this YouTube, I belive the guy adds the oil into the line.

Thu Jun 13, 2013 1:43 pm

Thanks Markz. That video kinda answers the question about mineral oil in the lines. I'm still wondering how much.

How much did you (anyone) put in and where?

Hans

Thu Jun 13, 2013 2:04 pm

hansh wrote: Thanks Markz. That video kinda answers the question about mineral oil in the lines. I'm still wondering how much.

How much did you (anyone) put in and where?

Hans

Here's another youtube video.

I refreshed my AC based on the feedback I got in the RedTek thred ~ five or so years ago. Last summer I just topped it off with another can. I find myself in need of another can or so, so I'm planning a more of a deep dive into the AC system. Full flush, etc. I kinda like it when the kids are complaining about being too cold in the back when it's 90 ouside. :lol:

cool is where it's at.
Mark

Thu Jun 13, 2013 2:30 pm

If you check Bentley, it tells you what goes where. If you want to ignore this post technical details, what you add is what you drain...as the amount in the compressor varies depending on RPM. The SD709 does not have a sealed crank, therefore whatever you add to the fill port on the top of the compressor (small bolt with 0-ring) will end up distributing itself through the system. The compressor "fill" is pretty much there to protect the compressor during the first few minutes of operation. Beyond that the technical manual on the compressor makes it clear that lubrication comes from oil circulating with refrigerant. It's also why you need to be carefull in terms of what you add. Ester100 is the base of Redtek's oil charge product.

Here is the technica manual for the SD709: http://www.sanden.com/originals/images/SD_Service_Guide_Rev.2.pdf

From the manual:

6.8.1 Oil Flow Theory
• Compressor lubrication occurs as the oil which circulates with the refrigerant passes through the compressor crankcase during operation. The Sanden SD series compressor achieves optimal durability and cooling performance when oil circulates through the system at a ratio of 3.3% to 8% oil to refrigerant. Excess oil can act as an insulator limiting heat transfer in the evaporator and condenser, while too little oil can negatively affect durability.
• Oil will collect in low pressure cool components (evaporator, accumulator and suction hose) of the refrigerant loop. For example a long suction hose which sags can collect several ounces thus reducing overall oil circulation ratio.

6psi refrigerant on the low side is Sanden's threshold..and the vanagon AC will not run at this pressure...the pressure switch will trigger the AC relay to turn off the compressor. Otherwise, you would damage the AC compressor due to oil starvation.

11.The amount of oil in the compressor after running for 10- 15 minutes should be as per the table at right. Determine from the table what the correct amount of oil should be for the particular speed used in step 3. (The table shown applies to SD5H14 and SD7H15 compressors. It is important that a quantity of oil remains in the crankcase. (these compressors wobble cylinder pumps like sd709).

Compressor RPM
Oil In Compressor fl oz

1000rpm -> 3oz
2000rpm -> 2.5oz
3000rpm -> 1.7oz
4000rpm -> 1.3oz
5000rpm ->1.2oz

So at 4000 rpm, ( compressor) only 1.3 ounces in compressor. if you were to shut down the immediately after 4000 rpm, I would expect only 1.3 ounces in the compressor crank/heads, plus the .5 ounces they suggest is left behind coating internals.

Ester 100 synthetic will mix ok with mineral, and is a better lubricant. From one of my previous posts:

Quote: denwood Wed Aug 29, 2012 11:27 am

--------------------------------------------------------------------------------

From Sanden themselves: http://www.sanden.com/originals/images/compressor_installation_instructions.pdf

If you're replacing a compressor from a system that has not been flushed..they are advising to drain the new compressor drain the old compressor...and only add to the new, the amount drained from the old. I believe Terry Kay has made the same recommendation the redtek thread.

I assumed that as Bentley calls for 5 oz in the fill plug, then that is what you would expect to drain out...not true.

Thu Jun 13, 2013 3:43 pm

denwood wrote: If you check Bentley, it tells you what goes where.
I would really appreciate it if you provide the location. I am not able to find any reference to the AC for my model year.
Quote: The SD709 does not have a sealed crank, therefore whatever you add to the fill port on the top of the compressor (small bolt with 0-ring) will end up distributing itself through the system.
Is this also true for the 508?
Quote: Beyond that the technical manual on the compressor makes it clear that lubrication comes from oil circulating with refrigerant.
True, but I don't know if this is all inserted via the fill port or if I add mineral oil to the H/L ports on a 508.
Quote: Here is the technica manual for the SD709: http://www.sanden.com/originals/images/SD_Service_Guide_Rev.2.pdf
I've read this...several times.
Quote: The Sanden SD series compressor achieves optimal durability and cooling performance when oil circulates through the system at a ratio of 3.3% to 8% oil to refrigerant.
This is the best info I have so far. However, I don't have my refrigerant in-hand yet and I'd like to get he system connected to pull a vacuum check on it. Given the fact that Sanden is concerned with accounting for the .5 oz coating the internals of the compressor, I'm not comfortable esimating how much remains coating the bucket used to drain the oil. Also, how do you distinguish old refrigerant from the ports from the mineral oil? That's another variation in he volume. If .5 oz is important, I'm not feeling like guessing.
I'd really like to know how much oil others who have an '84 with the 508 have added and where.
Quote: If you're replacing a compressor from a system that has not been flushed...
I'm not.
Quote: I assumed that as Bentley calls for 5 oz in the fill plug, then that is what you would expect to drain out...not true.
For an '84? I don't get it, you said I should use Bentley but, you think it is incorrect?

So, really, the '84s with the SD-508 should all be the same. I've done my homework and I've either not found the info or I'm not smart enough to understand it. Does anyone know how much and where?

Thu Jun 13, 2013 7:00 pm

Can't help you so much on the 84, however the 508 is just a 5 cylinder variation of the SD709.

If there is no fill port on the 508, then add via the low pressure side port before installing it. This is usually how it's done. Adding 5oz for example would not be correct, as the compressor will have differing amounts of oil in it depending on what rpm it was running at (for 5-10 min) when you shut it down. 3 oz would be a safe bet, assuming the last time it was used, the AC was shut off at 1000 rpm. The system is not as complicated as it seems..so if you did a full flush with a new compressor, adding 5 oz to the compressor (assuming you drained it first!), 1oz to the evap, 1 oz to the low pressure hose, and 1 oz to the compressor low pressure intake, would be just fine. The oil is carried everywhere by the refrigerant and will distribute more or less in the proportions listed below.

Keep in mind that the van has a lot more refrigerant (therefore oil) than a typical car. Your van has twice the amount of oil as in a typical Sanden setup in a car (4 oz vs 8 oz) so your margin for error is better.

Refrigerant Circuit with
Sanden SD 709 Compressor
(only Vanagon)

Condenser ~ 20 cc (0.7 fl oz)
Evaporator 60 cc (2.0 fl oz)
Receiver Drier 10 cc (0.3 fl oz)
High Pressure Hose 10 cc (0.3 fl oz)
Low Pressure Hose 10 cc (0.3 fl oz)

Total System Oil Capacity 240 cc (8.0 fl oz)

If it was my van, I would add 3 oz ESTER 100 to the compressor via the fill port. Rotate by hand to circulate the oil, reinstall. Given the Sanden rpm chart I posted above, and what was likely in your compressor when you removed it, then 3 oz is plenty. The oil will immediately start mixing with refrigerant in the compressor when it spins up, and circulate through the entire AC system with the refrigerant as a "solvent" of sorts. If you were to flush your system entirely, then adding 8oz to the compressor would in fact end up distributing the oil as per the chart above. The 508 vs 709 compressor likely has a volume difference, however the difference in terms of what is left "coating the internals" is likely very, very similar.

Been through the full flush/entire rebuild and a lot of messing around..so confidence with that information above is very high. You've already done more research on the topic than most mechanics would do :-)

Cheers,
Dennis.

Thu Jun 13, 2013 10:12 pm

Wow. Great info Dennis! Thanks for stricking with me. That was exactly what I needed to know. I can't wait to get it back together and stick the vacuum on it.

Hans

Fri Jun 14, 2013 9:43 pm

Enjoy the cool air :-)