Factory A/C Compressor: Is it any good? Upgrade Options?

[weekenderraf]

May be Sanden SP-10 is already DEC PAG oil?
I stil do'nt know if it is possible to replace the Sanden SP-10 with DEC PAG oil? If SP-10 is DEC this will not be a problem.

[LemonCove]

[Howesight]

"Pre-installation" of oil in new compressors is something that has always bothered me. Reputable companies pressurize moisture-sensitive AC parts like compressors, receiver-driers, and accumulators with nitrogen, but even then, the caps holding in the nitrogen are questionable. Once your system is moisture-free, then as long as you have sufficient refrigerant in the system, there will be no moisture ingress. This is due to the fact that the lowest pressure in your system will be about 26 psi, which, the last time I checked, is just shy of two times atmospheric air pressure. Moisture cannot travel from a low-pressure environment to a higher-pressure enclosed system. This is why moisture-related damage is ALWAYS a result of improper evacuation.

The newer PAG formulation helps keep the ambient moisture out of the compressor oil when on the shelf or in transit, which is great. However, the most important safeguards against moisture in the system are still, IMO, to dump the pre-installed oil, and then, just before evacuating the system, to install PAG from a new, never-opened container. Then the evacuation needs to be done for a sufficiently long time for the water to boil out of the system under vacuum. The time this takes depends on ambient temperatures, so don't try this in Colorado in December unless your garage is heated - - well heated.

Here's a link to a chart that shows the extreme importance of the level of vacuum one achieves in relation to the boiling point of water:

http://www.engineersedge.com/h2o_boil_pressure.htm

Note how much the boiling temperature of water changes so dramatically from 29.02 inches of mercury to 29.91 inches of mercury. If you are evacuating your system at ambient temperature of 59 degrees F, then unless your vacuum is at greater than 29.42 inches of mercury, YOU WILL EVACUATE NO WATER from your system. At those numbers, you have only equilibrium, and no boiling of the remaining water in your system.

Remember that all the nooks and crannies in your AC system need to have sufficient heat and sufficient vacuum to force the low pressure STEAM to your vacuum pump, or else you will have destructive moisture in your system. At these low vacuums, the motion of the steam to the vacuum pump is rather slow, hence the time allotment which, ideally, should be a few hours or even overnight if ambient temperatures are marginal for vacuuming your system.

You will thank yourself later, much, later, when your rejuvenated system is still performing perfectly five or ten years down the road whereas Gilligan's system is stranded, dead, on a desert Isle with no Ginger and no Mary-Anne and only the Skipper for company.
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'86 Syncro Westy SVX

[MsTaboo]

Howesight-Thanks for the information!
The ambient temperature while evacuating is one of those things you don't think of until someone brings it up and then it's a "duh, should have thought of that!" moment.

Unfortunately I'm having to deal with this right now as I try to button up everything on a Zetec reinstall. My shop is heated, but just. I'll be bringing in more electric oil filled space heaters to supplement my overhead heater for the evac.

I would imagine that elevation will also play a part in the efficiency of boiling out the moisture? I'm at just over four thousand feet here, so not Colorado, but not sea level either!

My new Zetec compressor came oil free and that and the Nostalgic condenser both came nitrogen filled and the seals held good, lots of gas blew out when breached. Of course I lost all that doing the pre-fitting of new hoses, fittings, etc. Had to be done.
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Currently:
'90 Syncro Westy 3 knob w/Zetec

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[Farf]

Altitude is not a factor in the evacuation of a system. A perfect vacuum would be 0 microns regardless of the altitude you start your process at. As Howesight said, the addition of heat will help vaporize any "water" in the system. As discussed in other posts its best to use a vacuum pump that can achieve low micron levels. 28.92" Hg or 25400 microns really won't get you to where you want to be without some serious heating of the system.

Edit: Your gauge if zeroed out when starting your vacuum will not read as low as one at sea level. This does not change how effective your evacuation is.



Altitude will have an affect on your pressure readings, higher head pressures and lower suction pressures. At 4000' altitude I don't think you will really notice much difference.

[djkeev]

[Farf]

Dave,

Thanks for the chart showing how altitude affects your gauge readings. Most DIY a/c people here on The Samba will use their gauges to measure the level of vacuum achieved with their vacuum pump, and it is important to understand this.

It is also important to note that vacuum pumps are rated by CFM and the ultimate vacuum "in microns" (reference point absolute zero pressure) that they can achieve. Microns being the more important factor.

Because of this, my comment to MsTaboo regarding altitude remains unchanged. Altitude will be a factor when referencing gauge pressure, but, will not have any effect on the level of vacuum achieved when referenced to absolute 0 pressure. Therefore, no changes to procedure need to be done with respect to moisture removal at altitude. The link provided below hopefully clears up the relationship between gauge pressure and absolute pressure at altitude.

Mike

http://www.esi-tec.com/news/2013/06/difference-between-gauge-and-absolute-pressure-measurement

"If you want to measure pressures that are not influenced by changes in atmospheric pressure, e.g. leak testing a completely sealed non-flexible container, you would use an absolute pressure sensor. If a gauge pressure sensor was used instead to measure the container pressure, and the barometric pressure changed, then the sensor’s reading would change, despite the fact that the pressure in the container remains the same".
​

[MsTaboo]

A quick look with google produced this:
https://books.google.ca/books?id=kg5tCgAAQBAJ&...mp;f=false
_________________
Currently:
'90 Syncro Westy 3 knob w/Zetec

The information age has morphed into the age of disinformation and willful ignorance. Agnotology!
Help the fight against Truth Decay.
Defend democracy, support Ukraine.

[Farf]

Edit: I think my attempt at answering MsTaboo's question regarding the relationship between altitude and its affect on a/c evacuation procedures was a bit "snarky". This edited version is how I should have answered in the first place. Sorry to all those who took it that way. This is an informative thread and I want to keep it that way.

MsTaboo,

Your link left me wondering??? Do I really need to purchase and actually read an automotive a/c manual?

So I think the link below is what you were referencing.

https://books.google.ca/books?id=Vr_Zm07ipB8C&...mp;f=false

After reading the article I realized that the author has made the same mistake in regard to referencing gauge pressure with absolute pressure as a lot of people do. His example using the elevation in Denver and boiling points of water from the chart is quite correct if Denver was located at sea level.

The chart that Dave provided with the % losses due to altitude is a handy reference for the reduced vacuum you can expect from your pump at various altitudes. This reduced vacuum is only due to the reduced atmospheric pressure one sees at elevation. In the authors example, the calculated maximum possible vacuum in Denver is 25.44" Hg, or looked at in absolute 0 terms, 25.44" Hg of atmosphere above the absolute 0 point that could be removed. In other words when starting your vacuum pump in Denver you are already at 4.48" Hg vacuum when referencing sea level. This point is your new 0 psig on your adjusted gauge, but you cannot use these gauge pressures to reference the chart for your boiling points of water. The chart is somewhat accurate using your gauges at sea level, but to get any useful data one would have to use a micron gauge especially at altitude. Most of us do not have access to a micron gauge and have to trust that our pumps will in fact reach a deep enough vacuum to be effective at moisture removal. New oil in the pump and a leak free system should be adequate for what we are trying to do.

I remembered a post from TK answering a similar question, I think its a good verbal explanation of what's happening.

[Terry Kay]

Why does simple stuff always become totally impossible here?

Make the altitude adjustment from the chart provided--mentally or write it down or copy it--you will forget the details, suck the system down, and reload it accordingly.

Don't read anything into this-- again, like most stuff, it isn't heart surgery.

What I would do way prior to asking anyone here in the hobbiest train of thought, is slide over to a local AC shop and ask a couple of quick questions, of what the gauge should be reading at full vacuum and again loaded up.

I know that air conditioning has been serviced in Denver since day one of AC and they will have the correct altitude adjustments all figured out.

Ask a professional in your area, that has done this AC work forever, for the correct gauge readings / figures first--then come here for some off the wall answer's, and offerings of some more reading materials that you really don't need.

Make it simple.

Air conditioning is just one of them items you can't possibly jip the job on.
it's all or nothing.
New hoses, dryer, expansion valve, compressor, and clean all of the snot out of everything original your going to use.
And then add new o-rings to all of the unions.

Then you have a chance of it operation properly, at whatever altitude you're going to be at.
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T.K.

[Farf]

Hi Terry,

I agree with you. This latest stuff is just to explain that you really don't need to torch your van with a flame thrower to get moisture out of the system regardless of what altitude your at. Yes, heat does make the evacuation process easier but with a decent pump and leak free system heating the system is not a must do thing.

I'm impressed by how much our fellow Samba members do know about a/c systems, and how much I continue to learn when pondering their questions. And I personally believe that its better to know why certain things are what they are, and not just accepted as facts from any one source on the internet. Myself included.

To twist a Samba mantra around...."Do the Research"

Hope you all have a great Christmas and New Year,

Mike

[Terry Kay]

Mike,

There is nothing etched in stone invthis AC work, there are too many variables.
If one guy was doing all of the work & only one, there would be concrete answers & solutions.
Problem is, say one specific operation to a hundred people, there will be 100 different takes on that info, twists & turns.

One guy here in PA has been attempting to get his AC up and running for at least 2 years, has been told point blank how to get the job done, and he is bound & determined to get it done his way, which is so far off the beaten path, it's ridiculous.
And he still doesn't have any air conditioning.

What's the correct vacuum reading supposed to be in Guadalajara Mexico?
Hell, I don't know, but if I was there I most certainly would ask an delegated AC shop that does nothing but AC work in that area, way before jumping into a general information forum, where there is many opinions on a lot of stuff, nothing specialized or concrete.
Guesses would be a good description, no hands on knowledge.

So, if your in Denver, do as the folks in Dever would do.

That's All.
This would be the most accurate info you could get.

Merry Chtistmas to you too.
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T.K.

[minnisp]

Hi Dave,

This thread and others have been a huge help. Thanks. I have a question since it has been a while since you posted the sanden compressors that would work. The SD7H15 - 8227 appears to have been discontinued and replaced by the http://store.sanden.com/index.php/4272.html. have you heard of anyone using this newer model and have it working ok? Mine is the sd709 model on 1989 GL manual with factory air. It is completely dead and it's getting hot in New Orleans it's time to make a move on AC..

[cobysmolens]

Just to perhaps clear up a little confusion about the lack of VW wiring diagrams for the Vanagon 83-85, early 86 AC system: To the best of my understanding, as I remember it, talking with the VW parts folks at the dealer back in my early days of servicing Vanagons (starting 1989 and on): This system was a dealer installed aftermarket system, and there were never any factory diagrams for this system. I believe it was mainly, if not exclusively, a dealer option in the US, possibly Canada as well. And wanted to say a HUGE THANK YOU to Dave for persisting in this! Just started looking at a customer's Westy with this exact system, and happy to have found this!
_________________
Coby Smolens
VoltZwagon!

Friendly service for vagabond vans (and their humans) since 1988.

[email protected]
(415) 747-5709

[scotty timmerman]

Im working on an 84 a/c system. the wiring diagrams that were posted here were a little different and were hard to read. i am currently trying to install a trinary switch. i have eddied the below diagram on how i think it should be wired. i have also posted the original wiring diagram. I would like to know if this is correct and any opinions on it. thanks

I have edited the wiring to do the following:

-when the evaporator fan is turned on by the switch it will activate the a/c clutch and turn on the low speed radiator fan.

-when the a/c clutch is turned off by the trinary switch or thermostat module the low speed fan will also turn off. (originally the radiator low speed fan is on all the time)

-the high speed fan will turn on/off with the trinary switches set pressure.

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71 ghia coupe: Build thread http://www.thesamba.com/vw/forum/viewtopic.php?t=511738&highlight=
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71 type 3 fastback manual
73 super beetle
57 oval: build thread: https://www.thesamba.com/vw/forum/viewtopic.php?p=8616563#8616563
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84 vanagon westfalia wolfsburg edition

[Abscate]

Absolute vacuum has no altitude correction. Most analoggauges use a differential pressure measurement so a reduced pressure on the air side will influence the vacuum reading.

All of this rendered moot by a leak test. With all new oring and workmanship your system should hold vacuum for days. If it holds for an hour, you can just pump on it and water will be gone, usually pump for2-3 hours with a dual stage pump.

If you have just opened the system and closed it within 24 hours, and don’t live in monsoon country, you don’t need to replace the drier like the Internet parrots claim. Just pump it down, check your work, recharge.
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.ssS!