A/C recommendations for the MB vehicles - Page 24 - PeachParts Mercedes-Benz Forum

Zulfiqar · #**346** 06-17-2016, 02:12 PM

after going through lots and lots of books I concluded that the only reason to use nitrogen is that its clean, dry and inert - compressed air quality is only as good as the filter/separator on the compressor.

the R22 along with N2 is used for sniffing out purposes, (good for leak checking on evap coils trapped deep inside a dashboard.

I assume the reason shops dont use nitrogen is because of cost (the air tank is right there always pumped up) - N2 bottle will require more money, space and has its own dangers too like asphyxiation and that the shops rely on the filter/dryer/accumulator to collect whatever moisture was pushed in.

The other reason home A/C techs usually have a n2 bottle is that they go to the A/C for repair rather than the car which comes to the shop for repair. a portable n2 tank is basically portable compressed gas medium - easy to work with without additional work - just like when racing teams show up to track events with some n2 tanks to run their tools and air their tires.

But in the end - nitrogen is far far better than using compressed air for A/C work - it doesnt add contaminant to the system you are working with, compressed air will unless you have some really good filtration.

leathermang · #**347** 06-17-2016, 02:15 PM

Quote:

Originally Posted by funola

So the 6 AC shops I called are also stupid and lazy because they do not use nitrogen/ R22? These are professional shops, the techs there probably had to go to school to learn the trade. Could it be that nitrogen/ R22 is just not a standard procedure for leak testing mobil AC?

You still have not read the EPA guide have you ?
Those shops do not think the extra time and labor is worth doing..

WHY do you not address the physical properties and theory behind the Nitrogen being used testing for leaks under pressure....

and the fact that the R22 can be legally vented into the atmosphere after a test to find any leaks.... and lets throw in again.. the fact that a dye used for leak checking will not find a leak in the evaporator or in lots of other hard to see...

Perhaps you do not understand the concept of ' Aficionado ' ...

aficionado Definition in the Cambridge English Dictionary

Perhaps you would understand if I described working on your own MB AC system as ' A Labor Of Love'.... I think our members trying to do their own AC work on these old cars fall into that classification... so them knowing the physics of the situation is entirely proper.. if they choose to use lesser methods that is their decision... it is their car..

but this is not how those shops see the job....

Do you deny that on home HVAC systems the industry standard of ' triple evacuation '.. meaning using the nitrogen multiple times AS the method of extracting moisture is legit ?

funola · #**348** 06-18-2016, 10:00 AM

Quote:

Originally Posted by leathermang

You still have not read the EPA guide have you ?
Those shops do not think the extra time and labor is worth doing..

WHY do you not address the physical properties and theory behind the Nitrogen being used testing for leaks under pressure....

and the fact that the R22 can be legally vented into the atmosphere after a test to find any leaks.... and lets throw in again.. the fact that a dye used for leak checking will not find a leak in the evaporator or in lots of other hard to see...

Perhaps you do not understand the concept of ' Aficionado ' ...

aficionado Definition in the Cambridge English Dictionary

Perhaps you would understand if I described working on your own MB AC system as ' A Labor Of Love'.... I think our members trying to do their own AC work on these old cars fall into that classification... so them knowing the physics of the situation is entirely proper.. if they choose to use lesser methods that is their decision... it is their car..

but this is not how those shops see the job....

Do you deny that on home HVAC systems the industry standard of ' triple evacuation '.. meaning using the nitrogen multiple times AS the method of extracting moisture is legit ?

Please stay on topic: Why Auto AC shops do not use nitrogen/R22 pressure test.

I will call more shops next week in different states like Texas, California, Arizona, Florida and see if I can find a shop that use nitrogen/r22.

Vstech still has not answered my question on his statement:

"to properly test a refrigeration (A/C) system for leaks you need PRESSURE! it must be in the form of a gas. NO liquid can be present or it invalidates the test. "

Which makes the test pretty much useless unless it is a brand new system before oil charging, or the system has been disassembled and the old oil flushed out and the system reassembled.

leathermang · #**349** 06-18-2016, 10:38 AM

I have told you why the shops do not do it.
You are the one trying to make why the shops do not do it as ' the subject' when it is not... the question is whether Nitrogen used under pressure with R22 added for a sniffer test agent is the best way to test....and it clearly is... other noble dry gases can be used but nitrogen is cheap... the R22 is LEGAL to VENT... and you should be able to understand the concept of testing the seals in their working direction...
The shops do not do it because they can get by without it... not because it would not be the better procedure.

ah-kay · #**350** 06-18-2016, 11:50 AM

Quote:

Originally Posted by leathermang

The shops do not do it because they can get by without it... not because it would not be the better procedure.

I am sure using N2 and R22 is a best way of performing leak test in an IDEAL world. There is always an ideal way and a down-to-earth shady mechanic way of doing things. This is a DIY forum where fund and resources is limited. A practical mechanic like me will improvise, make do, substitute, to achieve the same result. The end result will the the same IMHO. The A/C system is not the be all and end all of a car, there are other important components which makes up the car. They can fail at any time without notice on an old car. So move on.

ROLLGUY · #**351** 06-18-2016, 04:32 PM

Although I am not an A/C "professional", I do have quite a bit of mobile A/C experience. I have a local shop that I work with to do the leak checking, vacuuming, and charging on the systems I install. I can't say what other shops in my area use for leak checking, but I can say what my local shop uses and does not use. They/I use nitrogen and soapy water for checking before vac and charge, and UV light and a sniffer for afterward. They do not ever rely on a vacuum for leak checking. As far as I know, they do not have any R22 in the shop (does that give them an A- instead of an A since they don't use R22?). Very rarely do they miss a leak with the nitrogen, but when they do, they immediately recover the refrigerant and fix the leak. They employ the latest equipment for A/C work, as well as special schooling when needed (Chris the main guy). I believe their work to be top quality, and I have learned a lot working with them. I think they have done upwards of 20 vac/charges for me on my Sanden retrofits, and I am sure they will do many more......Rich

leathermang · #**352** 06-18-2016, 05:14 PM

Quote:

Originally Posted by ah-kay

I am sure using N2 and R22 is a best way of performing leak test in an IDEAL world. There is always an ideal way and a down-to-earth shady mechanic way of doing things. This is a DIY forum where fund and resources is limited. A practical mechanic like me will improvise, make do, substitute, to achieve the same result. ......

I am sure you did not intend to use the word ' shady' LOL... probably meant ' shade tree ' style...

Thanks for the thumbs up on the bigger picture and physics... since that really is not in dispute ...

BUT here is the part I think is short sighted and untrue in its implication in your description...
""" This is a DIY forum where fund and resources is limited.''''''

The MOST frugal way to do a job IS TO DO IT JUST ONCE....and it WORK correctly the FIRST TIME..... so , cheap nitrogen rented from the local welding shop... part of a 15 oz can of R22 ( which means it can be used legally for THREE separate TESTS... if you have to start over for some other reason.... or have more than one car to address....

Rollguy, I agree except for one large point.... without R22 or some SNIFFABLE ingredient ... your chances of finding a leak in the evaporator easily and quickly are really slim.... and that is one of the two leaks I had on my wagon 15 years ago...

ROLLGUY · #**353** 06-18-2016, 07:21 PM

Quote:

Originally Posted by leathermang

Rollguy, I agree except for one large point.... without R22 or some SNIFFABLE ingredient ... your chances of finding a leak in the evaporator easily and quickly are really slim.... and that is one of the two leaks I had on my wagon 15 years ago...

The SNIFFABLE ingredient is the refrigerant (R12, 134a etc). I have yet to have an evaporator go bad in a 123, and the leaks are found with the Nitrogen and soapy water. The installations I do are not the only work the shop does. Right now they are two weeks backed up, so I would be lucky to be able to slip in a vac and charge. All that to say that they know what they are doing, and have a great track record, even if they don't use R22. Even though I know that pressure and R22 is the best way to find leaks, I doubt I would be able to find a shop within a 100 mile radius that uses R22. There may be some that use a dry gas, but I wouldn't doubt most just vacuum to check for leaks.

leathermang · #**354** 06-18-2016, 08:50 PM

Quote:

Originally Posted by ROLLGUY

The SNIFFABLE ingredient is the refrigerant (R12, 134a etc). I have yet to have an evaporator go bad in a 123, and the leaks are found with the Nitrogen and soapy water. The installations I do are not the only work the shop does. Right now they are two weeks backed up, so I would be lucky to be able to slip in a vac and charge. All that to say that they know what they are doing, and have a great track record, even if they don't use R22. Even though I know that pressure and R22 is the best way to find leaks, I doubt I would be able to find a shop within a 100 mile radius that uses R22. There may be some that use a dry gas, but I wouldn't doubt most just vacuum to check for leaks.

So because You have never had a 123 evaporator go wrong... you argue against using that method... as an SOP for others ? I have only had two 123 evaporators and ONE of the TWO had a leak....

Why are you talking about ' finding a shop that uses R22 ? We are NOT talking about a shop needing their equipment to be R22 compatible... as one would have the problem with HFC's and a shop only having R12 and R134a equipment...
I am glad you admit to
''''. Even though I know that pressure and R22 is the best way to find leaks'''' Rollguy
If a person wants to try nitrogen and soap .. great... but if they want the best check... read SNIFF ..... and for the sniffer to cover the entire AC system in one move.... then they know what to do...

ah-kay · #**355** 06-18-2016, 11:31 PM

Quote:

Originally Posted by leathermang

So because You have never had a 123 evaporator go wrong... you argue against using that method... as an SOP for others ? I have only had two 123 evaporators and ONE of the TWO had a leak....

Why are you talking about ' finding a shop that uses R22 ? We are NOT talking about a shop needing their equipment to be R22 compatible... as one would have the problem with HFC's and a shop only having R12 and R134a equipment...
I am glad you admit to
''''. Even though I know that pressure and R22 is the best way to find leaks'''' Rollguy
If a person wants to try nitrogen and soap .. great... but if they want the best check... read SNIFF ..... and for the sniffer to cover the entire AC system in one move.... then they know what to do...

I don't think you get it. I think you live in a ivory tower. If the shops, the professional, do not use it then it is either not practical, expensive or cumbersome to use R22. You don't understand the law of diminishing return. R22 may catch 0.1% of the leak but if the shop can make do with N2 and soap water to catch the other 99.9% then why bother? If you are happy with using R22 then so be it. It does not mean everyone has to do it or follow you. Next subject.

leathermang · #**356** 06-18-2016, 11:55 PM

I have a can ...... I think 15 oz.... sitting on a shelf here in the house... easy to get from Ebay....

You are completely misrepresenting the effectiveness of soap and water... that is totally unrealistic for finding a leak in the evaporator.... or many places on the car where insulation covers the joints.... or mid hose.... as was other leak on my wagon... that long line which goes up over the engine leaked...and the evaporator leaked....

I think I paid $130 for my nitrogen tank... I bought it because I do not like to pay demurrage ,,, I do not use my gases very fast... might take years to empty one..
and I have a plasma cutter.. so in addition to testing ac systems.... I can use it for that....

How a Plasma Cutter Works

https://en.wikipedia.org/wiki/Demurrage

'''Gas cylinders
The rental fee for a gas cylinder assessed by the vendor until the tank is returned.'''

I am about as frugal and practical as anyone you will run across... and I understand the physics..... and I hate to do things twice when a little extra work can make the first time a slam dunk.

gskurka · #**357** 06-19-2016, 04:32 PM

Guys,
This explaination might help..... I found the article at: Aircondition.com
Greg

What are the Benefits of Leak Testing with Nitrogen?

We found the answer to that question in an article which first appeared in the May/August 2001 edition of Cool Profit$ Magazine. This article was written by John Noble, and has been reprinted here with permission from Cool Profits Magazine.

Understanding the Basics

System Residues hide leaks. Sludge and residues coat the interior of system components and temporarily seal corrosion pits, fissures, seams, seals, o�rings, and other small leak points. Some of those residues include refrigeration oils, acids, desiccant, pulverized metal, Teflon piston ring material, brazing fluxes, dye particles, etc.
Overcoming Residue Surface Tension: Leaks are harder to find because leak testing is performed with the system turned off. Lost are the benefits of an operating system: a) constant washing of interior surfaces of components; b) higher operating pressures that encourage leaks. With a system at rest, the undisturbed residues mentioned above are able to coat the insides of the evaporator, condenser, compressor, and other components. When Residue Surface Tension is greater than the interior pressures� ability to displace it, there is no leak occurrence, thus no leak detection.

Residue Displacement: If surface tension is the culprit, then how do we overcome it? Answer: By adding 4-ounces of chlorine-based refrigerant R-22 to the system. R-22 disturbs the surface tension. We follow that by pressurizing the system with 175-200 psi of nitrogen. Both are cheap.

At the higher system pressure, the R-22 overcomes the residue surface tension and forces the leak path to reopen. Now, enough R-22 gas is available so that leaks are detected easily. The R-22 is the residue-displacing agent.

R-22 summary. R-22: (a) creates a leak path because of its oil solubility and residue displacement potential; (b) is more readily detectible by electronic leak detectors than HFCs; (c) is non visual-dependent, unlike dyes, thus can be used effectively to locate leaks in enclosed areas; (d) will not cross-contaminate nor cause any harmful consequences to CFC, HFC, nor blend refrigerant systems (i.e., after leak testing an HFC (R-134a) system using R-22, there is typically zero percent cross-contamination if evacuated afterwards).

Nitrogen summary. Nitrogen has the following qualities: (a) inert, very dry and non-flammable; (b) does not go into solution with refrigeration oil to create non condensable pressure problems (i.e., after leak testing an HFC (R-134a) system using R-22 and nitrogen, there is typically zero percent non condensables (nitrogen or air), if evacuated afterwards).

Diluted Liquid Soap. Speed is important to technicians when performing a leak test. Large and medium size leaks can be quickly located in exposed areas such as under hood components by applying diluted liquid dishwashing soap directly to suspected leak points.

Multiple Leaks. If a large leak is discovered repair it and perform a follow-up leak test. Leak tests should be performed following each repair until all leak points are found and fixed.

Pinpoint versus Area Testing Pinpoint Accuracy. Technicians need to know exactly where leaks exist. Consequently, leak testing needs to be pinpoint accurate, regardless whether by visual or non-visual means. With dyes, the detection is strictly visual and general area, not pinpoint. Dyes do not provide the rapid and finite definition of the Combination Method [non-visual: electronic leak detector detecting the nitrogen-pressured R-22, and, visual: diluted soap solution bubbling].

Electronic Leak Detectors. Heated diode leak detectors are currently the best non-visual, dependent leak detection instrument for sensing a gaseous leak. They have the necessary characteristics of sensitivity, repeatability and recoverability (after a leak), which are so important.

Releasing Test Mix. The EPA approved the releasing of the �test mix� (R-22 & nitrogen) with the stipulation that: �All existing refrigerant within the system be recovered properly, and a 102mm (about 4�) mercury vacuum drawn on the system.�

By their definition, the R22-nitrogen test mix used for leak testing is not considered a refrigerant and therefore may be released to atmosphere. Their rationale is that one tiny loss which results in the discovery and repair of a leak reduces the greater loss over the life of a system. It�s better than multiple recharges of refrigerant and multiple losses to atmosphere.

Note: We�ve learned that the R22-nitrogen test mix should be released outside the building via copper (or other) tubing to prevent fouling the air inside the shop. This prevents false alarms by the leak detector. Also, always maintain a well-ventilated work area.

Summary
There is currently no equally effective (in all situations) substitute for the combination leak test method described above. It has neither the problems nor shortcomings of dye. I have heard the argument that nitrogen is dangerous. Well, the stationary industry has been using it for at least 60 years, and my company has been using it since 1973. Some of the major stationary manufacturers think that is important enough to dedicate a section of their training manuals exclusively to its use for leak testing their a/c systems. It is not unsafe, unless one uses it improperly. Mobile a/c technicians are simply untrained in its use. What a shame, it is so simple and effective and easier, safer, and cheaper, etc.

Once upon a time, folks were afraid to fly in an airplane that didn�t have a propeller�it was thought to be too dangerous. I encourage any a/c technician to get a good quality nitrogen regulator and bottle of nitrogen from a welding supply store. Set the regulator to 200 psi. It is safe to use with all conventional a/c systems, and will not damage any system components.

Make sure that the nitrogen bottle is secured to a wall or in a dolly, and that everyone in the service department is taught not to fool with the regulator setting. Or, install an Allen head set screw and lock nut with the regulator so that it can�t be adjusted once it is pre-set. We have safely tested a/c system components at 200-psi nitrogen pressures on over 40,000 tests. Remember, 200 psi is only about 50 psi higher than the compressed air lines used by you and every other technician nation wide. I encourage all technicians who aspire to become more professional in a/c service to invest in a good quality nitrogen regulator and bottle. Then take the time to practice the method. You will be doing a service to yourself and your customers. $$$

About the Author: Before opening an automobile repair business, Cool Flow, Inc. founder John Noble spent 7 years in the aircraft service industry, and prior to 1971 worked as an FAA certified airframe & power plant technician. During the next 4 years he began to make the transition to specializing in automobile a/c related services. Today, the company is currently undergoing another transition into development of several a/c related products.

vstech · #**358** 06-19-2016, 08:00 PM

WORD!

Nicely put.

Quote:

Originally Posted by gskurka

Guys,
This explaination might help..... I found the article at: Aircondition.com
Greg

What are the Benefits of Leak Testing with Nitrogen?

We found the answer to that question in an article which first appeared in the May/August 2001 edition of Cool Profit$ Magazine. This article was written by John Noble, and has been reprinted here with permission from Cool Profits Magazine.

Understanding the Basics

System Residues hide leaks. Sludge and residues coat the interior of system components and temporarily seal corrosion pits, fissures, seams, seals, o�rings, and other small leak points. Some of those residues include refrigeration oils, acids, desiccant, pulverized metal, Teflon piston ring material, brazing fluxes, dye particles, etc.
Overcoming Residue Surface Tension: Leaks are harder to find because leak testing is performed with the system turned off. Lost are the benefits of an operating system: a) constant washing of interior surfaces of components; b) higher operating pressures that encourage leaks. With a system at rest, the undisturbed residues mentioned above are able to coat the insides of the evaporator, condenser, compressor, and other components. When Residue Surface Tension is greater than the interior pressures� ability to displace it, there is no leak occurrence, thus no leak detection.

Residue Displacement: If surface tension is the culprit, then how do we overcome it? Answer: By adding 4-ounces of chlorine-based refrigerant R-22 to the system. R-22 disturbs the surface tension. We follow that by pressurizing the system with 175-200 psi of nitrogen. Both are cheap.

At the higher system pressure, the R-22 overcomes the residue surface tension and forces the leak path to reopen. Now, enough R-22 gas is available so that leaks are detected easily. The R-22 is the residue-displacing agent.

R-22 summary. R-22: (a) creates a leak path because of its oil solubility and residue displacement potential; (b) is more readily detectible by electronic leak detectors than HFCs; (c) is non visual-dependent, unlike dyes, thus can be used effectively to locate leaks in enclosed areas; (d) will not cross-contaminate nor cause any harmful consequences to CFC, HFC, nor blend refrigerant systems (i.e., after leak testing an HFC (R-134a) system using R-22, there is typically zero percent cross-contamination if evacuated afterwards).

Nitrogen summary. Nitrogen has the following qualities: (a) inert, very dry and non-flammable; (b) does not go into solution with refrigeration oil to create non condensable pressure problems (i.e., after leak testing an HFC (R-134a) system using R-22 and nitrogen, there is typically zero percent non condensables (nitrogen or air), if evacuated afterwards).

Diluted Liquid Soap. Speed is important to technicians when performing a leak test. Large and medium size leaks can be quickly located in exposed areas such as under hood components by applying diluted liquid dishwashing soap directly to suspected leak points.

Multiple Leaks. If a large leak is discovered repair it and perform a follow-up leak test. Leak tests should be performed following each repair until all leak points are found and fixed.

Pinpoint versus Area Testing Pinpoint Accuracy. Technicians need to know exactly where leaks exist. Consequently, leak testing needs to be pinpoint accurate, regardless whether by visual or non-visual means. With dyes, the detection is strictly visual and general area, not pinpoint. Dyes do not provide the rapid and finite definition of the Combination Method [non-visual: electronic leak detector detecting the nitrogen-pressured R-22, and, visual: diluted soap solution bubbling].

Electronic Leak Detectors. Heated diode leak detectors are currently the best non-visual, dependent leak detection instrument for sensing a gaseous leak. They have the necessary characteristics of sensitivity, repeatability and recoverability (after a leak), which are so important.

Releasing Test Mix. The EPA approved the releasing of the �test mix� (R-22 & nitrogen) with the stipulation that: �All existing refrigerant within the system be recovered properly, and a 102mm (about 4�) mercury vacuum drawn on the system.�

By their definition, the R22-nitrogen test mix used for leak testing is not considered a refrigerant and therefore may be released to atmosphere. Their rationale is that one tiny loss which results in the discovery and repair of a leak reduces the greater loss over the life of a system. It�s better than multiple recharges of refrigerant and multiple losses to atmosphere.

Note: We�ve learned that the R22-nitrogen test mix should be released outside the building via copper (or other) tubing to prevent fouling the air inside the shop. This prevents false alarms by the leak detector. Also, always maintain a well-ventilated work area.

Summary
There is currently no equally effective (in all situations) substitute for the combination leak test method described above. It has neither the problems nor shortcomings of dye. I have heard the argument that nitrogen is dangerous. Well, the stationary industry has been using it for at least 60 years, and my company has been using it since 1973. Some of the major stationary manufacturers think that is important enough to dedicate a section of their training manuals exclusively to its use for leak testing their a/c systems. It is not unsafe, unless one uses it improperly. Mobile a/c technicians are simply untrained in its use. What a shame, it is so simple and effective and easier, safer, and cheaper, etc.

Once upon a time, folks were afraid to fly in an airplane that didn�t have a propeller�it was thought to be too dangerous. I encourage any a/c technician to get a good quality nitrogen regulator and bottle of nitrogen from a welding supply store. Set the regulator to 200 psi. It is safe to use with all conventional a/c systems, and will not damage any system components.

Make sure that the nitrogen bottle is secured to a wall or in a dolly, and that everyone in the service department is taught not to fool with the regulator setting. Or, install an Allen head set screw and lock nut with the regulator so that it can�t be adjusted once it is pre-set. We have safely tested a/c system components at 200-psi nitrogen pressures on over 40,000 tests. Remember, 200 psi is only about 50 psi higher than the compressed air lines used by you and every other technician nation wide. I encourage all technicians who aspire to become more professional in a/c service to invest in a good quality nitrogen regulator and bottle. Then take the time to practice the method. You will be doing a service to yourself and your customers. $$$

About the Author: Before opening an automobile repair business, Cool Flow, Inc. founder John Noble spent 7 years in the aircraft service industry, and prior to 1971 worked as an FAA certified airframe & power plant technician. During the next 4 years he began to make the transition to specializing in automobile a/c related services. Today, the company is currently undergoing another transition into development of several a/c related products.

leathermang · #**359** 06-19-2016, 08:41 PM

WORD!!! X3

funola · #**360** 06-20-2016, 07:49 PM

I called 6 more shops today. 3 were major national chains: Firestone, Midas, Sears, the rest were independent shops specializing in Auto AC. None of them had Nitrogen/ R22. To find leaks, all recharge with refrigerant/ dye/ detect with sniffer/ UV light.

Called up a welding supply. To rent a Nitrogen tank requires an account and cost $15 a month just for the tank, smallest size is 20 Cu ft, gas and regulator ($100) is not included. 20 cu ft of Nitrogen is $30. If you don't use it up, they don't give you a refund for what's left in the tank.

R22 is not cheap because it is being phased out by the EPA due to it being ozone depleting. Going rate on Ebay is around $50 for a 15 oz can.

A good electronic UV or infra red sniffer is $400 to $500. You don't want to buy a $20 sniffer from Ebay because they false alarm

For DIY, spending $500 to $600 for the equipment and gases to do Nitrogen / R22 testing just does not make sense. None of the auto AC shops use it. What does that tell you?