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Old 06-12-2012, 05:47 PM   #1
kenn921
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Default ac question

system had no freon in it. vacuumed for 10 minutes, held 30" vacuum for 10 min. charged 1.5 lbs. ran system with gauges hooked up. ac on high speed, condensor fan comes on. hi side at 150 psi, lo side at 35psi. noticed that compressor clutch doesnt cycle on/off. stays on. is this normal in a 2001 sl1?

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Old 06-12-2012, 06:14 PM   #2
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Default Re: ac question

In one word, yes. No Saturn compressors cycle at all as we have better designed compressors; variable displacement compressor that default to the lowest output at start up and ramp up according to heat loads (more cooling needed). This allows year 'round use of a/c while using heat for comfort and control windows from fogging up, using less power when freezing conditions aren't needed like in the winter. The older style compressors that output 100% also use the most power all the time whether needed or not.

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Last edited by fdryer; 06-12-2012 at 06:19 PM..

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Old 12-16-2012, 04:35 PM   #3
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Default Re: ac question

So what specifically is wrong with one when it no longer ramps up past about 100 psig on the hide side, and barely cools? Ours is a 2001, SL1, Saturn.

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Old 12-16-2012, 05:24 PM   #4
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Default Re: ac question

Late edit:

So what specifically is wrong with one when it no longer ramps up past about 100 psig on the high side, when fully charged, and barely cools? Could be the expansion valve, or only the compressor? Is the problem part serviceable if on the compressor? IF either one is possible is there a way to test and verify which it is?


Ours is a 2001, SL1, Saturn.

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Old 12-16-2012, 05:52 PM   #5
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Default Re: ac question

Well, for one thing, you'll have to spend some time reading about refrigeration fundamentals to accurately answer the question. Without any refrigeration knowledge, your system leaked, period. The difference between understanding refrigeration and how your system leaked out enough R134a over time was pointed out by your observation of seeing only 100psi with a/c on. Simply put, normal a/c system pressures @2000 rpm (Saturn specified rpm when measuring low/high side pressures) will show low side always around 30-35 psi while the high side will vary from 150-250+ psi. High side pressures vary relative to ambient temperatures and humidity. There's more to a/c than simply measuring pressures and topping off.........................

Your incomplete descriptions, to me, spells a system that's already lost refrigerant, and not a compressor fault. A compressor failure can result from too many refill attempts, using sealer, incorrect troubleshooting, and incorrect a/c repairs.

What do you mean by fully charged? There's only one way to know what a full charge of R134a is - starting with an evacuated system empty of all air and moisture (in preparation for leak testing and recharging) then filling with the amount of R134a specified on labeling. Any other method used is guessing.

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Old 12-16-2012, 07:06 PM   #6
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Default Re: ac question

Quote:
Originally Posted by fdryer View Post
Well, for one thing, you'll have to spend some time reading about refrigeration fundamentals to accurately answer the question. Without any refrigeration knowledge, your system leaked, period. The difference between understanding refrigeration and how your system leaked out enough R134a over time was pointed out by your observation of seeing only 100psi with a/c on. Simply put, normal a/c system pressures @2000 rpm (Saturn specified rpm when measuring low/high side pressures) will show low side always around 30-35 psi while the high side will vary from 150-250+ psi. High side pressures vary relative to ambient temperatures and humidity. There's more to a/c than simply measuring pressures and topping off.........................

Your incomplete descriptions, to me, spells a system that's already lost refrigerant, and not a compressor fault. A compressor failure can result from too many refill attempts, using sealer, incorrect troubleshooting, and incorrect a/c repairs.

What do you mean by fully charged? There's only one way to know what a full charge of R134a is - starting with an evacuated system empty of all air and moisture (in preparation for leak testing and recharging) then filling with the amount of R134a specified on labeling. Any other method used is guessing.
Thanks for the courtesy of a reply, but please leave the grade school stuff for others. I have been doing AC work since I was in diapers 57 years ago, I am also a hands on Chemical engineer. Now that we have that out of the way...

Now please assume I know what I am talking about, and if you have some useful insight, other than lectures about leaks, leaks, leaks please post them. I already read way too many of your posts all over this section today about leaks, leaks, leaks.

I want to know what is different and newish about the Saturn compressor and expansion valve versus the other old style common systems.

Now to try and answer some of your questions:

To my knowledge the system has never ever been serviced since day one. 230,000 miles, and last 2 owners had it since about 110,000 miles 6-7 years ago, me being the second of the two. IT has worked flawlessly until now.

Yes it has a leak, small leak, and I added R-134-a to test the rest of it, and the high side pressure gauge never got over 100-105 psi, and the needle vibrates wildly from 85-105 on the high side (sign of bad valve seal to me). The compressor started making a mechanical internal noise at about 90 psi as the system was recharged (I added 12 oz) and the high side pressure climbed from about 65 to 100, initial pressures with compressor running before I added any significant charge was 20/65 low/high sides. I had to add a little to get the compressor clutch to engage. The initial system pressure (off) was about 45 psi (as best I recall), which confirmed to me a low charge, and your notorious LEAK, LOL!!!!

I suspect the compressor is bad, but you mentioned these compressors are a new breed, and I see there is a replaceable part listed for the later year Saturn compressors that from what I read could cause a similar problem to the one I have here, but it did not show that part on the 2001 (as far as I have seen so far, but I just got started digging into this one). It was some kind of variable regulator on the compressor I think, starting in 2006(?).

Also I want to make sure there is not a special history of bad expansion valves that fail in such a way as to make the compressor noisy enough to sound like a bad compressor since I am not familiar with the Saturn expansion valve yet. That is why I posted my question here and not on an A/C repair site. I was hoping someone here might know something about Saturn A/C systems, other than "They leak"?

Edit: Here is a link to the compressor part I mentioned above:

http://acpartshouse.com/showitem.asp...ontrol%20Valve

Last edited by Ecomike; 12-16-2012 at 07:12 PM..

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Old 12-16-2012, 07:56 PM   #7
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Default Re: ac question

If you don't want the grade school stuff then let us know right off the bat that you know AC systems. If you do this then you don't have to give us something that to me appears to be attitude, I could be wrong on the attitude but to me it seems to be attitude.

AC problem

100 PSI on the high side at what RPM?
Ambient temperature is?
What is the low side pressure?
System of course was recovered, vacuumed and checked for vacuum loss before being recharged to the correct ampount of R-134 by weight?

The S-series AC compressor is a variable displacement swash plate compressor not scroll. The compressors tend to be trouble free. The expansion valves also tend to be trouble free but I would suspect it before a compressor.

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Old 12-16-2012, 09:39 PM   #8
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Default Re: ac question

If my replies seem to be lecturing about refrigeration, you'll find not many here that know anything about vehicle a/c systems. Whether you're a chemical engineer and gifted with skills in a/c repairs since you were in diapers, the more information you post just verifies that the LEAK has played a large role in disabling the a/c system until you tried a refill to unknown amounts (12 ozs + what remained in the system). A gamble by adding another 8 ozs may raise pressures but its your gamble. Not knowing the exact amount of R134a in a system just skews pressure readings. I presume you know about the temperature/pressure relationships in a closed system. If you do then you'd understand how incorrect amounts of R1344a will throw off pressure readings. As mentioned, no pressures measured against service manual recommendations at 2k rpm prolongs troubleshooting. VDC's, when Googling for information, will describe this type of compressor as not an add-on modification but a well improved compressor from older style constant displacement types. Varying the displacement may seem new to you but has been around since Saturn came out in 1995. That makes it approximately 17 years for Saturns and who knows how much earlier in GM's family of cars. Compressors and thermal expansion valves are reliable and have not shown any history of premature failures in comparison to straight displacement compressors. What makes them fail is lack of understanding in troubleshooting as most insist a compressor failed or other imagined issues when finding the leak that caused the original problem is almost always overlooked. A noisy compressor is one of the first signs of a leaking system. Noise equates to lack of oil lubrication with the compressor already scraping itself internally, damaging the plain aluminum chamber walls. Have you seen the disassembled compressor (donated to me) and the damaged vanes in my picture album?

If you want to get on board about vdc's then post the pressures with the engine idling at 2k rpm, not at idle. All the engineering degrees are meaningless if you fail to follow guidelines. These suggestions aren't mine, they're from the service manual.

In my limited time here on Saturnfans, only one or two members that followed service manual guidelines when a/c troubleshooting and acquired all the equipment needed for a full a/c repair were able to determine their compressors failed and replacing it along with a receiver/filter/drier fixed their issues. These members are fully aware of all the pitfalls when it comes to "DIY" a/c repairs. One is a Vue owner with less than 10 years on the original compressor when it was determined a compressor finally failed with partial cooling at idle but adequate at all other speeds. Extensive testing, evacuating, recharging, and full pressure monitoring narrowed the problem to the compressor.

If you have equipment then by all means evacuate, leak test, and recharge with the specified amount of R134a and post pressures. This isn't what I would do but it is written in the service manuals to do so to accumulate data before determining what course of action to take. Almost anything you do without the pressure/temperature charts is guessing.

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Last edited by fdryer; 12-16-2012 at 09:47 PM..

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Old 12-16-2012, 10:03 PM   #9
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Default Re: ac question

Quote:
Originally Posted by ssicarman View Post
What is the low side pressure?
+1

This is very important. If the low side pressure is high, the compressor is likely the problem, but if the low side pressure is correct, it is doing its job (the displacement is varied to maintain a constant low side pressure, so if the low side pressure is correct, the compressor is operating at a low displacement, as it should, and the problem (if there is one) is something else).

Quote:
Originally Posted by ssicarman View Post
The S-series AC compressor is a variable displacement swash plate compressor not scroll. The compressors tend to be trouble free. The expansion valves also tend to be trouble free but I would suspect it before a compressor.
It's a vane type compressor, actually (like most power steering pumps). Displacement is varied by a cam plate that adds or removes "extra space" on the compression side.

As long as there is an appropriate amount of oil in the system, they are pretty reliable.

I have seen an S-Series expansion valve fail, causing a very similar concern.

If the valve sticks in the closed position, or does not open as far as it should (based on evaporator outlet temperature), it will take little displacement to keep the low side pressure low, so despite the excessive restriction of the TXV, the high side pressure will be low. This can easily be misdiagnosed as a faulty compressor: the low side pressure is what gives it away. If the compressor is maintaining the correct low side pressure, it is not at fault, regardless of a low high-side pressure.

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Old 12-16-2012, 10:53 PM   #10
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Default Re: ac question

"Have you seen the disassembled compressor (donated to me) and the damaged vanes in my picture album?" The only picture I see is a rotary vane style:

http://www.saturnfans.com/photos/sho...ressor/cat/500

But ssicarman says the compressor is a "variable displacement swash plate compressor not scroll"

This looks like a good break down .......See page 2-9

http://student.ccbcmd.edu/~smacadof/...ompressors.pdf

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Old 12-16-2012, 11:53 PM   #11
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Default Re: ac question

Saturn variable displacement compressors are the rotary vane type. That's all Saturn uses. No swash plate at all as shown in the disassembled one.

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Old 12-16-2012, 11:54 PM   #12
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Default Re: ac question

Quote:
Originally Posted by PlasticCarsRock View Post
+1

This is very important. If the low side pressure is high, the compressor is likely the problem, but if the low side pressure is correct, it is doing its job (the displacement is varied to maintain a constant low side pressure, so if the low side pressure is correct, the compressor is operating at a low displacement, as it should, and the problem (if there is one) is something else).



It's a vane type compressor, actually (like most power steering pumps). Displacement is varied by a cam plate that adds or removes "extra space" on the compression side.

As long as there is an appropriate amount of oil in the system, they are pretty reliable.

I have seen an S-Series expansion valve fail, causing a very similar concern.

If the valve sticks in the closed position, or does not open as far as it should (based on evaporator outlet temperature), it will take little displacement to keep the low side pressure low, so despite the excessive restriction of the TXV, the high side pressure will be low. This can easily be misdiagnosed as a faulty compressor: the low side pressure is what gives it away. If the compressor is maintaining the correct low side pressure, it is not at fault, regardless of a low high-side pressure.

The only reason I highly suspected the compressor, is it sounds like a bad valve or rod knock in an engine, or for a rotary vane like a busted vane floating around and the high side pressure needle vibrated extremely fast from about 90 to 105 psig. Could a TXV valve failure do that? Have you seen one that failed do that? Let me add the compressor was noise free until it reached about 90 psig on the high side, with about 9 of the 12 oz already added. Also the ambient was about 70 F.


I will need to rerun the gauge data collection, but as I recall I let the 12 oz can slowly fill the system, and the low pressure started at about 20-25, ran up to about 40 as I opened the bottle to add refrigerant (maybe as high as 80 at first before the clutch engaged), and then dropped from 80 low side to about 20/50 low/high side, then both slowly climbed at idle (about 800 rpm) for about 15 minutes as the refrigerant was added. With about 2-4 oz left to go (out of 12) it reached about 30/90 and then started making the mechanical noise that made me the think the compressor was about to croak. I am not 100% sure how high the low side was the last 5 - 10 minutes, but it seems like 30-40. I was paying more attention to the noise and the high side gauge then.

I know I revered the engine a few times but as I recall the low/high side pressures did not change with engine rpm at all. I will check and verify this. Also This is to my knowledge the first time it ever needed R-134a added, and there is no sign of a leak that took oil in the refrigeration system with it, that I could see. I have seen plenty of those, I know what they look like, so I do not believe oil loss is an issue here, yet.

Last edited by Ecomike; 12-17-2012 at 12:08 AM..

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Old 12-17-2012, 12:35 AM   #13
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Default Re: ac question

This link shows the General Motors V-5 Compressor (Zezel) which is the compressor that the s-series uses.
This thread mentions and gives a link. My searching the net shows the same compressor as the V-5. It also matches my experiences in doing compressor autopsies of S-series compressors.

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Old 12-17-2012, 12:40 AM   #14
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Default Re: ac question

Lack of oil lubrication is due to loss of R134a; when a leak occurs, slowly or quickly, oil lubrication ceases as liquid R134a under pressure moves oil around the system to eventually wind up being suctioned back into the compressor. Oil circulation relies on R134a at full capacity. Compressors are not self oiling. With no visible leak being marked with compressor oil, the leak can be coming from anywhere, one or both service valves with caps left loose. Caps serve as the primary seal. Loss also occurs over the lifetime of a/c systems at calculated rates so 15 years may go by without issues for normal wear and tear.

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Old 12-17-2012, 04:44 PM   #15
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Default Re: ac question

Quote:
Originally Posted by ssicarman View Post
This link shows the General Motors V-5 Compressor (Zezel) which is the compressor that the s-series uses.
This thread mentions and gives a link. My searching the net shows the same compressor as the V-5. It also matches my experiences in doing compressor autopsies of S-series compressors.
Quote:
Originally Posted by fdryer
Saturn variable displacement compressors are the rotary vane type. That's all Saturn uses. No swash plate at all as shown in the disassembled one.
Quote:
Originally Posted by Plasticscarsrock
It's a vane type compressor, actually (like most power steering pumps). Displacement is varied by a cam plate that adds or removes "extra space" on the compression side.
Hmm, there seems to be a large difference of opinion as to which compressor it is, a rotary vane, or a V-5? Unless I miss understood you?

http://student.ccbcmd.edu/~smacadof/...ompressors.pdf

The online stores show this:

http://www.oreillyauto.com/site/c/se...02&make=Saturn

A DCV11s compressor, but I can not find anything online that shows the guts of that model.

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Old 12-17-2012, 05:09 PM   #16
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Default Re: ac question

For anyone in doubt, take a look at FDryer's photo gallery. He has pictures of a disassembled compressor, and it's quite obvious that it's a vane-type compressor.

And, if you still don't believe us, at least listen to Saturn.

Quote:
Originally Posted by Saturn Field Service Manual: A/C Description and Operation
The Saturn compressor is a variable displacement rotary vane type pump. The rotor assembly houses five lightweight vanes that extend outward contacting the cylinder wall creating the compression area. The compressor has an internal control valve that allows it to change its pumping capacity or displacement, reacting to heat loads on the air conditioning system. The range of displacement can vary from 5 percent (5.5 cc) to 100 percent (110 cc). The compressor's natural or resting state is at minimum displacement.

The compressor should not be making noise during normal operation. Causes of noise include mechanical damage, severe overcharge, lack of oil, or filling quickly with liquid refrigerant, instead of gas (which can lead to mechanical damage, although it's pretty rare).

If the low side was 30 or lower at 2,000 rpm, the compressor is good. If the low side is much over 30 psi (certainly anything near 40 psi), and the system is known to be properly charged, the compressor may be worn or damaged (unless it is particularly hot--higher than normal low side pressures can be normal if the HVAC fan is sucking in particularly hot air).

Note: it is very important that this test be performed at 2000 rpm. At idle, it is normal to see higher low side pressures.

If the compressor is new/rebuilt, or if it hasn't been used in a while, the vehicle should be driven with the a/c on for a little while before checking anything. This may be necessary to extend vanes that are stuck from lack of use. (Some high-ish rpms would be a good idea, too, but nothing near redline or anything crazy like that.)

A bit of flutter in the gauges is normal (it will rise with each compression pulse of the compressor), but abnormal (excessive) flutter does indicate bad valves. The only way to tell the difference, as far as I know, is by comparing the readings to another vehicle with the exact same a/c system (known to be working properly).

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Last edited by PlasticCarsRock; 12-17-2012 at 05:24 PM..

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Old 12-17-2012, 06:07 PM   #17
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Default Re: ac question

Quote:
Originally Posted by Ecomike View Post
Hmm, there seems to be a large difference of opinion as to which compressor it is, a rotary vane, or a V-5? Unless I miss understood you?

http://student.ccbcmd.edu/~smacadof/...ompressors.pdf
Unfortunately, this document doesn't show the rotary vane type vdc. Try Searching the library in ackits.com for compressors and exploded diagrams. I found them there after disassembling the compressor for show and tell. Look for Zexel pdf's.

Quote:
Originally Posted by Ecomike View Post
The online stores show this:

http://www.oreillyauto.com/site/c/se...02&make=Saturn

A DCV11s compressor, but I can not find anything online that shows the guts of that model.
oreilly's shows the correct replacement. Unless you're willing to perform extensive testing to determine where the failure lies, running 230k miles without any servicing seems to be one of the longest running a/c systems and may be all about normal wear and tear that points to the compressor. There are several ways to consider this repair but all are major repairs/rebuilding a worn out system.

1-Testing involves what was described previously to measure pressures at 2k rpm with known amounts of R134a to compare against the service manual temp/press chart for accuracy.

2-Cut to the chase and rebuild the entire system according to the service manual recommendations; disconnect all hoses, remove the compressor, receiver/drier, and thermal expansion valve for replacement, flush out all hoses, condenser coil and evaporator coil to remove all old oil and any contaminants that may damage the replacement compressor, add make up oil to all major parts according to service manual guidelines, reassemble everything using new O-rings lubed with R12 mineral oil, and evacuate/leak test/recharge with R134a. This is Saturn's procedure for the best protection against contaminating or damaging a new/rebuilt compressor. This is the most expensive repair to fully restore a system to factory condition.

3-Modify step 2 somewhat by examining the oil from the system when fittings are disconnected or compressor removed and drained. Refrigerant oil is clear to light honey colored when new. Circulating for years will cause the steel vanes to scrape the aluminum chamber walls and create fine aluminum dust that changes the oil color. Expect either a dark gray oil that's opaque or translucent. Feel it for grit as this grit is adding to the wear and tear of the compressor. Most rebuilds will involve replacing the compressor and filter/drier while leaving the txv in place. Replacing the txv on the firewall is just insurance against a worn out one. Your choice. Flushing should be a serious consideration to rid the system of old oil and any crap to prepare for rebuilding back to factory condition. New oil used for a fresh start.

4-Replace the compressor and filter/drier without any other work and adding make up oil. The least expensive repair and not guaranteed by anyone since old oil remains in the system, everywhere.

...
VCX NANO

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Old 12-17-2012, 08:21 PM   #18
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Default Re: ac question

I found the DCV11A (not the DCV11S) here:

http://www.ackits.com/diagrams/Dieselkiki.pdf

The Zexel pdf is not a rotary vane.

http://www.ackits.com/diagrams/Zexel.pdf

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