TheSamba.com :: View topic - How much refrigerant oil when converting to r134a?

Fri Jun 08, 2018 8:15 pm

I have revived a 1990 Vanagon waterboxer. All done with the exception of the AC. The system was empty of freon (it had sit in a grove for 4 years).Pumped the system down and it held vacuum well. Converted it to r134a. Cools well but my question is, how much refrigerant oil to add. I gather that ester oil is the oil of choice but how much to add? The manual states that the system holds roughly 8 ounces of oil. However, how much of that would remain in the system if it just slowly lost freon and had no sudden hose burst which would undoubtedly cause a significant loss of oil along with the freon evacuation. The conundrum I face is guessing how much oil to add at this point. Any insight is appreciated.

Fri Jun 08, 2018 8:46 pm

There is actually no way to know. But you should at least hear this: you need to empty all of the oil out of the system if changing from freon to r134a as they are incompatible and need to be replaced and changed and the lines purged of all air again. Instead you may find that there are compatible refrigerants that you could use that may have a lower pressure and possibly not need to completely drain the system. Look around and maybe find a better solution than R134a, it will be in your long-term best interest. You will need to do some removal of oil regardless and see that it is in good condition.

Look for thread titled RedTek (abit pricey), or such others as Envirosafe R134a replacement, like 3 cans for $20 total.. I'm bad at spelling BTW..

Sat Jun 09, 2018 8:32 am

A far cheaper alternative to Redtek is Envirosafe - it works fine. $5 for a 6oz can that's equivalent to 16oz of R134a. I bought a case of 12 when I was sorting my A/C, as I knew I'd be finding leaks and replacing hoses eventually. :)

https://www.es-refrigerants.com/products/w/id/173/...etails.asp

Sat Jun 09, 2018 10:40 am

fxr wrote: A far cheaper alternative to Redtek is Envirosafe - it works fine.
x2...same r12a refrigerant as RedTek, plus "fresh pine scent"... :lol:

(not kidding) :roll: <shrug>

http://afabdistribution.com/AFAB-Enviro-Safe/ENV-5-oz-12a.htm

- Dave

Sat Jun 09, 2018 12:42 pm

On the assumption that the OP wants to stay with the R-134a refrigerant, the rule of thumb is about 1/3 of the oil will stay in the compressor, less than a 1/3 scattered in the hoses/pipes and a little more than 1/3 in the evaporator & condenser (not sure where I saw that). Anyway, the bottom line is, the oil will be pretty much scattered throughout the system at any given time. So, it will take a flush to get it all out.

Use PAG 100 Oil with R-134a.

As some have stated, the total amount is about 8 ounces. Based on my experience, I feel certain that amount can be plus or minus an ounce without any negative results. I'd rather be a smidge over than significantly low.

After two summers of less than desired results (long story), last July, I replaced all the hoses/fittings on my 84 Vanagon AC system which has a Sanden SD7V16 Compressor as on the TDI ALH engine and installed R-134a (I did flush). It functioned very well and is doing fine now.

Having said the above, I'm sort of inclined to agree with the suggestions to go with something besides R-134a. There is a "window" for the correct amount to be installed to obtain the best cooling affect. Also, the older Vanagon AC system (like in my 84) is barely on the edge of being an acceptable candidate for R-134a, in my opinion. I suspect the later models, such as yours and my 89 may be a bit better. There is a long Thread on Red Tek. I am not familiar with the EN V5.

EDIT: A bit of info on Red Tek: http://www.redtek.com/win_12a_prod.html

Sat Jun 09, 2018 3:12 pm

thanks to everyone who commented. I welcome ALL feedback. (retired auto mechanic here but retired about the same time r12 did. :-)

Sat Jun 09, 2018 4:34 pm

That stuff about mercaptans turning to acid is made up Internet shinola by the way. The trace amounts aren’t what kill systems but moisture will.

Sun Jun 10, 2018 2:39 pm

R134A is compatible with mineral oil. If you feel your system has not lost any oil don't add any. One of the reasons for the composition of the R134A blend was to be compatible with mineral oil. If you add oil, add mineral oil, or you should remove all oil in the system if you want to use another oil type.

You could add a can of R134A that has an oil charge in it if you are worried that your oil level is low, it won't be much and you should not have any issues. You will need to add that can upside down to get the oil in your system, just throttle the valve most of the way shut and add it slowly.

John

Sun Jun 10, 2018 3:40 pm

vanagonjon wrote: R134A is compatible with mineral oil...

Interesting statement, I've never seen anything supporting this, all of the data that I've read states that mineral oil and 134a should not be run together in a system. For example:

From: www.vasa.org.au/wp-content/rtp/volume1/RTPRETV1B3.pdf

Myth No. 1
“I have heard some people retrofit to R134a with no oil
change - no addition of PAG or Ester whatsoever with
no problems”
The test data clearly shows oil return/circulation is close to zero when mineral
oil is used with 134a. The reason why some retrofits do not fail is that the
operating conditions of the vehicle are city cycle/low speed where a
significant portion of oil is retained in the compressor.
Under these conditions oil circulation/miscibility/solubility is far less critical.
The problem is of course that with continued use eventually the oil will be
displaced into the system and not returned - but after a period of 2 years
(nominal) a compressor failure is unlikely to be directly attributed to the
insufficient oil return.
The second problem is far more serious. When the vehicle is placed into a
high speed/highway cycle environment the compressor simply pumps itself
dry due to insufficient oil return in a much shorter time frame.

Mon Jun 11, 2018 3:45 am

I re-read my seminar material and realize that I was a little confused. Yes, the mineral oil doesn't return well with R-134A, but since most of the system is essentially laid out flat, it should be ok. You can add some of the correct oil and it will mix ok with the original oil.

John

Mon Jun 11, 2018 6:30 am

Seems as if we don't know weather it was already converted or not. More likely, it was purged of Freon, and now waiting for 'new' stuff...

Thing about R134A is its pressure range. Its working pressure is way way higher than Freon, and the RedTek and Envirosafe have a lower working pressure than Freon. That made it an easy choice for me. Can't imagine taking a 28+ year old system and ask it to operate at double the pressure.

Mon Jun 11, 2018 8:03 am

tampaguy, Since your Van has been sitting for a while and is about 3 decades old, like all the Vanagons, it will probably need some work to have reliable AC.
Remove the compressor and drain out as much oil as possible through the hose connections and drain/fill plug. Disconnect all the fittings and install new O-rings. You can usually get 134A "retrofit" kits at auto parts stores that have an assortment of O-rings. The original O-rings used in most R12 systems will leak if used with 134A.
Leave the the filter/drier unit off and flush out the system. You may want to have a shop that does a lot of AC work do this for you. In many states only shops that do AC work can buy the flushing fluid. Many people use all kinds of solvents to flush the system. This may or may not work.
Then install a NEW drier and the compressor. Add the recommended amount of oil in the "Bentley" book for your year. Vac down the system and add the 134A. Ops check and you should be good unless there are leaking hoses, other bad components or the compressor is worn out.
And yes there is a way to check the oil level in the Sanden compressor, but it is rather complicated and may be outside the capabilities of most of us.
The procedure was on the Sanden website. You need to do what I outlined above then run the system for a while, evac and recover the refrigerant, then remove the plug from the compressor. They detail how to make a "dipstick" to check the oil level. Then add or remove until level is in range. Reinstall plug evac and recharge system.
Simple yeah? I have done this quite a few times, but the amount spec'ed by the vehicle maker was always correct in a clean system. So I stopped doing this check. This check is only valid if the system has been run.
Also adding oil, if you don't start with an empty system, can be trouble. I have fixed some AC systems where people kept adding "oil charge" cans as the thought was "the refrigerant is leaking so is the oil". With too much oil the system performance, cooling, is reduced and the compressor could be noisy leading to unnecessary replacement. Way too much oil will wreck the compressor.
I'm not going to wade into the discussion of other refrigerants except to say that if the van ever ends up at a repair shop for AC work with something other than R12, R134A, or the new stuff (I think it is 1234) they will not work on it.