Need Air Conditioning Help

The point raised about load (and also ambient temp, operating/airflow conditions across the condenser) is critical when evaluating system pressures. Given the conditions provided those pressures look perfect to me. If a fan was placed in front of the car to encourage more airflow across the condenser (as if traveling down the road) you would see the high side come down significantly.
The only concern I have is that you stated after stopping the compressor the system pressures only stabilized a small amount. I am assuming you only watched the gauges for a very short time. The pressures on the low and high side should be the same after about 5 to 7 minutes after shutdown. If the pressures dont equalize that may be an indication there is a fixed restriction in the system like a stuck expansion valve or a plugged dryer/other component. But, because the system did not go into a vacuum on the low side while in operation I`m confident your system pressures will eventually equalize. You will discover if this is the case when you put the system into service under various conditions. Good luck :TU:,
Tom Mooney

 

Yes very short time after shut down. I'll check it again 5 to 7 minutes after shutdown and see what I get. Also how long do I need to run it to make sure it's good and ok?

 

If you didn't purge the gauge/ manifold lines of air before you put the gas in, you're screwed. Air is a non-condensible and also carries moisture with it unless you did this on Mars. The frosting of the suction pipe tells me it is under charged and the 205 psi head pressure tells me it has air in it if you have pipe frosting at the same time. You will need to suck the gas back out and I recommend pulling it down 3 times to make sure you get ALL of the air out. Yes air molecules can be embedded in the walls of rubber hoses. If you have access to dry nitrogen, you should break the vacuum each time with that before you put the gas in which will break the last vacuum pull. Dry nitrogen will help to scavenge the moisture out. If not make sure you pull at least 28.5" of vacuum to make sure the moisture is vapor as it is pulled out and no liquid droplets remain. 29.5" is better. Good that you let it stand overnight to prove the seal. You don't need to do the three vacuum pulls overnight, just the last one. As stated, get as full a load on the system as possible and you should observe the radiator thermal fan clutch engage as the system puts heat in the condenser. When that happens, there will be a noticeable change in radiator fan flow and noise.

The expansion valve is a critical part of the equation and is designed to maintain proper superheat of the suction gas. With a POA valve you should have two small copper lines each coming from opposite sides of the expansion valve. One has a bulb to attach to the suction pipe with pipe clamps and must be covered with the tar seal so that moisture can't condense on the bulb. The other side connects to the bottom of the POA valve. This is meant to make sure that the expansion valve opens up if the pressure at the POA gets too low. This keeps the gas flow up at low load and keeps oil flowing back to the compressor under this condition. That is why it is important to have the full charge in there to keep the oil flowing around the system.

 

When I charged it I didn't use manifold gauges. The gauges I have are for 134 only and I had to put fittings on to be able to use those with the vacuum pump and I only used them during vacuum. I took them off when I charged it. To charge I had a can of r12 and a short hose only. After I charged with a 12 oz can I would check the pressure with a single gauge and short hose. It is probably an undercharged system with only 2.5 cans of freon and a 4 oz oil charge on an empty system. Should I open and evacuate the system?

 

Wow. A ton of BAD advice being spewed here.

First things first. Please describe the load you are experiencing when the compressor is running. Any A/C compressor can bring an engine's idle down several hundred RPM, especially an A6. Are there any unusual noises coming from the compressor? Keep in mind some noise is normal with an A6. With 2.5 cans in the system the compressor will be loaded down.

Next, stop worrying about not purging the air out of your short line, and DO NOT dispose of your charge. That tiny bit of air that may have made it's way into the system is immaterial and WILL NOT make a difference. Also, a new receiver dryer (which you claim to have) is more than capable of capturing any remaining moisture. That is what it is there for.

What size cans of freon did you use? I am guessing you need to add a little more freon and then you are good to go. There is a good chance you do not have a problem.

Finally, I don't agree with others saying that you will damage a compressor running it with an undercharged system. I've run them on empty systems (by mistake) and the compressors did not show one sign of being harmed.

 

I used 12 oz cans. I will have to try again and see what noises I am getting. I'm honestly afraid to run it at all with the input here although the little bit I have since the initial run seems to be ok. Before it only made noise as I was charging it and it was hot. It sounded like the compressor was bogging down as well as a little bit of bearing noise. I shut it down and the next day it was fine and blew cool with no noise, but I didn't run it long and just enough to get the pressure readings. Maybe 10 mins at most.

 

I guess you are talking about me. First my credentials - I am a registered professional engineer in 6 states - all of them hot and humid states - and have practiced in the field of Mechanical Engineering for HVAC for over 31 years. I have been an active member of The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) since 1986 and have chaired or been a full voting member of several technical committees of that society. So much for my "office" credentials. As part of my professional engineering practice, I have been the engineer of record for commercial and/or industrial refrigeration systems employing R-11, R-12, R-22, R-113, R-123, R-134a, R-407c and R-717. I also have extensive field experience spanning 3 decades in the construction, commissioning and trouble shooting of these systems. So I know a little bit about what is being discussed here.:TU: Maybe I should explain what I am talking about here and why I recommended certain things because at times I am guilty of thinking that other folks are up to speed to the level I just described. Pulling all of the air out of the system is not possible. You have to pull a perfect vacuum like outer space so there is always a "little bit of air" in the system. The 3rd law of thermodynamics is in full effect here. However, the presence of non-condensables in the system means that you have a gas in the system that doesn't condense. What does this mean? When R-12 changes phase (at a given temperature and pressure) the liquid will occupy 292 times less space than the gas per lb. Air won't do that because it can't condense (at least not at the conditions found in your A/C system). Therefore it is taking up and wasting space in the system. How much is a "tiny amount ... that is immaterial"? Only the end result can speak to that because a tiny amount is there as you correctly pointed out. But, the result is higher head and suction pressures and the evaporator body temperature doesn't drop to the temperature found on the pressure-temperature chart for R-12. GNSX can take your advise and pull a vacuum and not worry about a little air in the gauge lines, but I can guarantee he will be back on this board asking why his center outlet temperature is 48 - 50 F and not 38 - 40 F like his other buddies running R-12. Before I converted over to R-134a in my GS, I was able to get 35 F out of the center outlet with 105 F outside in stop and go traffic here in humid Atlanta GA - following the steps I outlined while charging the system. Let's move on to water. Water is actually a refrigerant (R-718) because it can evaporate and condense, but doesn't work well for A/C systems. You are correct in that the receiver/dryer is to remove moisture from the system. How does it do this? The receiver actually has two functions (according to the 1971 Buick Chassis Service Manual) - 1) it assures a column of liquid refrigerant is always available to the expansion valve (that is why there are bubbles in the sight glass of an undercharged system) and 2) it has a desiccant bag (silica gel) to remove the moisture. I have been involved with over 60 HVAC systems using desiccants such as silica gel and lithium chloride and they all have the same characteristic - they absorb moisture when cool and release moisture when warm, so after the car warms up, the moisture absorbed by the desiccant if you insufficiently vacuumed the system was released to the system after it warmed up and back again when it cools off. The little bag of silica gel can "wear out" and that is why it is recommended to replace the dryer when you overhaul the system. A heat gun (not a torch) on it helps when pulling the vacuum and can reactivate the desiccant. If you pull a vacuum on your system at 28.5", the moisture inside will boil at approximately 80 F. At 29.5" the moisture will boil at approximately 52 F. As you can see, unless the environment in which you are doing this operation is at a relatively warm temperature, you won't get the moisture out, thereby loading the desiccant and rendering it at reduced capacity. My little el cheapo vacuum pump from Sears will only pull about 27" vacuum so I need to start the engine and get the environment good and hot up to at least 115 F for the moisture to boil off. This includes full heat in the recirc position to get the evaporator hot - disconnect the compressor please. I am guessing that GNSX is not using an industrial quality vacuum pump like they used at the factory - I might be wrong on this by supposing facts not in evidence. At 29.9" vacuum, water will boil at -12 F so the deeper the vacuum produced, the more moisture is removed and the difference of a little bit of vacuum is dramatic. Also I have not seen R-134a manifold sets (which GNSX says he is using) you see for sale at the local Pep Boys display a vacuum on the low side dial, so I do not think that GNSX is sure what vacuum he is pulling. I might be making an erroneous assumption here, he may be using a commercial or industrial quality manifold set or he may have found an automotive one elsewhere that reads vacuum accurately. Moving on to oil. The A6 compressor has an oil sump on the bottom and a pump underneath the back cover. This oil is for the shaft (including the back side of the shaft seal) and swage plate bearing lubrication only. It does not lubricate the reed valves or pistons. This lubrication is dependent on the ester oil used in R-12 system that has the proper miscibility with the refrigerant so that it can be carried in the gas and liquid. Yes you can run the compressor and it won't grenade in your face, but you will reduce it's life- no question by running at a low charge for a long period of time. It is a physical fact if you don't have the proper charge volume and mass flow of refrigerant with miscible oil moving around, you won't transport the proper amount of oil back to the compressor. I know I am long here:boring:, but there is a lot more engineering and good practice behind the repair of these systems and how to achieve the expected levels of performance. Do it right, and your air will be ice cold.

 

In other words, you're over qualified and anything less than perfect will simply not work? :Smarty:

 

Removing your line after pulling a vacuum is just as bad as not pulling a vacuum at all. Air in the system in nooooo good...

 

It may seem that way, but I do acknowledge that one can not completely pull all of the air out of the system. However, there is a dramatic difference in the amount of moisture you pull out with just a 0.4" difference in vacuum. I feel like the advise I offered was not "bad" and felt the need to explain in depth what my reasoning was since it may not be obvious on the surface. GNSX seems confused over the whole issue and is looking here for help and advise and not aspersions cast between offerors of that advise.

 

... I'll take your bad advice anyday :TU:

THANKS for posting :beers2:

 

I respect and appreciate someone being a perfectionist but I try to be realistic. I have run many A/Cs that I put together WITHOUT pulling a vacuum and they worked fine if the rest of the system was OK and I purged the air from the system using freon. It's not ideal, and I don't suggest that people do this but it CAN be done.

Telling someone to immediately dump an expensinve R12 charge due to the possibility of a miniscule amount of air being in the system is downright wrong.

 

I did not think I told GNSX to "dump" the charge but told him to "suck" the charge out which implies a recovery unit. Again, I am guilty of thinking everyone else is up to speed. Dumping R-12 is illegal per the Clean Air Act of 1996 and my post was not intended to be interpreted that way. We all can point to our successes - particularly as the result of a short cut - and we learn a lot more from our failures. I have had enough failures over 3 decades and have been fortunate enough to learn from some real refrigeration pros why you would engage in certain practices. Having a clean refrigeration circuit eliminates a variable when troubleshooting these systems. ou:

 

So if he needs to recover the system then that means the refrigerant is considered contaminated and the freon must be destroyed NOT reused. Again, bad advice at this point because there is not convincing evidence that his charge is contaminated.

 

Plus the assumption the guy has a ton of gear to do this kind of work. Most of us are shade tree at best. Starting your first post with:

was kind of alarmist IMO.

I've done one system in my old Jeep without a vacuum because I did not have the hoses, gauges and pump to do it and the A/C blew cold the two following years while I owned it, and it probably still does. My Skylark I used better practices though still not ideal, but I did vacuum it and let it sit a couple hours and it held so I charged it with the off the shelf 134a cans and watched the pressures. They lined up well, and I don't know what temp the vents blow, but on a 103*F I had the windows up and the A/C set to less than max because max made me cold. It might be 35*F or it might be 45*F, in either case, it's cold enough for me. The OP won't know if his is cold enough for him unless he drives it. If it's not making screeching noises and the pressures look decent on the gauges, then drive it and try it.

 

There is some pretty good info on the web about how a recovery unit works. It is not about contaminated refrigerant so much as it is about say replacing a valve in the line or some other kind of service and then separating the air, small solids and oil contaminants and placing the old and cleaned refrigerant back in the system. GNSX probably should go to a shop that has one of these and let them charge it professionally. You can buy one in the range of $600 to $800 if you want to do this at home. Just be careful because the EPA does have a bounty program for people caught doing this without the proper license. ray: http://www.mastercool.com/media/69500-INST_LR.pdf

---------- Post added at 05:40 PM ---------- Previous post was at 04:22 PM ----------

Yes you are probably right and I upset GNSX a little. My apologies. He is probably wondering what he got into. I did talk a little bit about some "shade tree" approaches and I can share my limited resource method. I converted over to R134a in my GS due to the expense and difficulty in obtaining R-12. The little 14oz cans can be purchased at the Wal Mart for $9.99 each. The system takes about 3 cans. You will need a new expansion valve for R-134a available at NAPA and is made specifically for A body conversions to R-134a. You will also need the green O-rings available at the same store. There is a lot more to R-134a conversion, but that is a long discussion. The shade tree method that works for me is that I use the el cheapo vacuum pump mentioned previously ($150 at Sears) and my R-12/R-22/R-500 gauge set connected to the high side port of the compressor with the low side gauge since it reads vacuum. Knowing your vacuum reading makes the difference between cold air and cool air. If you can get 28.5" then you only have to heat the system past 80 F. I my case a high compression big block Buick with long tube TA headers makes all the under hood heat I could ever need. I have replaced the POA valve in my system with the Year One (Old Air Products sells the same thing) compressor cycling clutch type fitting and switch. By connecting the vacuum pump to the high side Schrader valve, this leaves the R-134 fitting on the low side available to connect your can and tap hose. Like GNSX, pump it down and leave it overnight to prove a good seal. Then tap the can, and run the piercing valve all the way down. Open it back up enough to hear a little gas coming out of the end of the hose then connect the can right side up to the low side. Turn the can upside down and back the tapping valve all the way out. This will rapidly empty about 1/2 to 3/4 of the can - with the compressor off. Look at your vacuum gauge over at the compressor and see to make sure it registers over 10 psi positive. Take the vacuum hose off and you should not get air into system when you do this. Put your high side R-134a fitting on this port and connect your el cheapo R-134a manifold set you bought at the Pep Boys like I did. Now turn the system on full fan and full outside air. Ensure the compressor clutch is engaged and the rest of the can of R-134a should be in the system. Tap a second can and repeat the process where you hear some gas coming out and after it is connected, turn it upside down so the system pressures come up rapidly. You can connect the low side of your Pep Boys R-134a manifold and see where you are. If you are low on both high and low sides, then tap the third can and repeat the purging, reconnection with the gas coming out and turning the can upside down. Run about 1/2 of the third can in and then check pressures again. Tweak the charge by adding a little gas (can right side up) and letting the expansion valve settle after all the upset you just gave it. Test drive it and see how it does. In my case I have the air temperature coming out around 42 F, outside air between 90F and 95F with outside dewpoint above 70 F. Not as cold as the R-12, but the R-134a usually is not because its specific heat (ability to transport btu's around per lb of refrigerant) is not as high as R-12 and will require larger than stock condenser and evaporator to reach the same performance. You may get colder in Nevada since you don't see this high of a dewpoint on the evaporator but your condensing temperatures are higher so there is a tradeoff. A similar procedure can be followed for R-12, but you need to know what your vacuum level is and avoid any introduction of air to the system you just evacuated. They key is to just let a little gas flow through the hose before you connect the can to the system. A 5 to 10 seconds will purge it. I think the R-134a conversion makes life a lot easier if you don't have all the goodies required by the EPA and provides acceptable air temperatures. If you go and pay at a shop for this service look for the recovery units, dry nitrogen, etc. This tells you that your money will be well spent and they are likely to be licensed professionals.

 

:TU:

This is the good stuff. This is essentially what I had done (except to a '77 A4 system) and the only thing I'd add to it is I used a warm bowl of water to keep the R-134a can from frosting over. I had trouble getting my first can completely empty, so I got a bowl of warm/hot water and set the can in it while the engine/system was running to get that last bit out. Sped up the process if nothing else.




And on a side note, I'm at 6,500ft elevation and low desert humidity, so my vacuum readings and system performances are skewed a bit

 

It is all good stuff. There are a number of other threads out there on this forum asking why their air coming out is not as cold as it use to be. I was attempting to answer that and detail the explanation with facts and science.:Smarty:

 

After sleeping on yesterday's discussion, I decided to do a little research on R-12 issues. The serious expertise in R-12 is retiring or dying off - literally. DuPont scaled down production about 20 years ago leading up to its outright ban by the EPA under the 1996 Clean Air Act. However the research found some interesting things about R-12.
As the use of alternative refrigerants grows, so does the risk of cross-contamination. A survey by the Florida EPA revealed some startling results. When they tested the refrigerant recovery tanks in about 100 shops, here is what they found:

1. Thirty-eight percent of the recovery tanks showed some type of contamination! Independent repair garages and service shops had the lowest rate of contamination, but it was still 32% (nearly one out of three). Used car dealers were the worst, with 71% of their recovery tanks (almost three out of four) showing signs of contamination.
2. Air contamination was the worst problem, being present in 22% of the tanks tested overall. But cross-contamination between R-12 and R-134a was also found in 15% of the tanks. The most cross-contamination (29%) was discovered in used car dealers.

Alternative refrigerants that have been found acceptable for automotive applications include the following blends:

• Free Zone (RB-276). Supplied by Refrigerant Gases, this blend contains 79% R-134a, 19% HCFC-142b and 2% lubricant.

• Freeze 12. Supplied by Technical Chemical, this blend contains 80% R-134a and 20% HCFC-142b.

• FRIGC (FR-12). Made by Intermagnetics General and marketed by Pennzoil, this blend contains 59% R-134a, 39% HCFC-124 and 2% butane.

• GHG-X4 (Autofrost & McCool Chill-It). This blend is supplied by Peoples Welding Supply and contains 51% R-22, 28.5% HCFC-124, 16.5% HCFC-142b and 4% isobutane (R-600a).

• GHG-HP. Also supplied by Peoples Welding Supply, this blend contains 65% R-22, 31% HCFC-142b and 4% isobutane (R-600a).

• Hot Shot\Kar Kool. Supplied by ICOR, this blend contains 50% R-22, 39% HCFC-124, 9.5% HCFC-142b and 1.5% isobutane (R-600a).

The suppliers of the alternative blends say their products typically cool better than straight R-134a in systems designed for R-12, and do not require changing the compressor oil or desiccant in some cases. Changing the desiccant to XH-7 is usually recommended if an R-12 system is converted to R-134a. The desiccant should also be replaced if a blend contains R-22 because R-22 is not compatible with XH-5 or XH-7 desiccant. The recommended desiccant in this case would be XH-9. DO NOT USE ANY FLAMMABLE REFRIGERANT! If you get in a fender bender in the front, you could literally go up in smoke.
The suppliers of the alternative blends also insist the fractionation problem is exaggerated and do not foresee any major problems with recovering and recycling their products.
One supplier of these products say they sold several million pounds of their alternative refrigerant, so the public is accepting it.
Less dangerous but equally illegal is bootleg R-12 that is being smuggled into the U.S. from offshore. Though most of the industrialized nations have stopped manufacturing R-12 (production ended in the U.S. December 31, 1995), R-12 is still being made in some Third World countries including Mexico. Some of this product is finding its way past customs in mislabeled containers or concealed in various ways. The EPA warns that much of the refrigerant it has confiscated thus far is of poor quality, contaminated by air, moisture, R-22 and other substances. The EPA has worked with customs authorities and the FBI to make a number of arrests. Fines for violating the clean air rules can run up to $25,000 per instance.
Counterfeiting branded product is another scam that is being perpetrated to turn a fast buck in today's market. Cylinders of counterfeit Allied Signal Genetron R-12 have reportedly been turning up in various parts of the country. The cylinders do not contain R-12 but some "unknown" refrigerant. Allied Signal says the counterfeit boxes do not have cut-outs where lot numbers strapped on cylinders would appear and there are no bar codes or white painted stripes on the sides. The number "Q 1167" may also appear on the bottom of the packaging. The cylinders themselves may be marked with a pressure-sensitive decal whereas the genuine product has markings printed on the cylinder itself.
The oil research is also interesting and may shed light on the original problem experienced by GNSX.
OILS USED IN AUTOMOTIVE A/C SYSTEMS
MINERAL OIL
Mineral oil is used in all old R12 (Freon) systems. It has worked well for years and would be the recommended lubricant for all R12 applications. R12 has a high affinity for mineral oil, meaning it takes mineral with it as it travels through the system. Mineral oil does not mix with R134a and there for not usable.
PAG OIL (Polyalkylene Glycol Oil)
PAG oil is used OEM (Original Equipment Manufacturers) in their R134a systems. PAG oils will soften paint which can be a major problem. PAG oils are harsher on o-rings and seals. PAG oils may cause skin irritations. PAG oil is very hygroscopic (absorbs moisture from the air) and must be kept in closed metal containers.
POLYOL ESTER OIL (Retrofit Oil)
Polyol Ester oil (Ester for short) or retrofit oil as its' sometimes called is the preferred oil to use when you are performing a retrofit. Ester oil is recommended by most after market manufacturers and rebuilders. Ester oil mixes with and is compatible with mineral oil. Ester oil can be used with R12 and R134a refrigerants. Ester oil is not as harsh to o-rings, seals and paints as PAG oils. This is the oil that comes in or is supplied with the compressors that come from Everco, Murray, and Four Seasons. When you are doing major repairs you could prepare the vehicle for later retrofit.

The PAG oil has been reported to cause issues with expansion valves hanging up in R-12 systems as well as the fact it is not miscible with R-12 and won’t move around the system. If GNSX put a 4oz can of PAG oil into the system that might explain the core problem.

 

I used mineral oil and real r 12. The oil charge and freon I have are from the 70s and 80s. Like this