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Survey...Dry Ice recovery method

uunfews on Thu October 29, 2009 12:04 AM User is offline

For those that use this method for recovery, what percentage of refrigerant were you able to typically recover from the total amount in the system?

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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

NickD on Thu October 29, 2009 6:23 AM User is offline

Could go back and even ask why you want to recover, know that some of the techs on this board say the only right way to check the refrigerant in a system is to recover and measure it, nice if you have a charging station. But on the other hand, all MVAC systems leak, what I could not find is an EPA defined acceptable leak. Most good electronic leak detectors claim a sensitivity of detecting a one ounce per year leak. If a vehicle like yours is slightly below that and is nine years old now, that equals nine ounces! And for a system that takes only in the 24 ounce range, someone would have to check that for your vehicle, that's over a third of your refrigerant that has leaked out, and more than likely, this degree of leaking can be considered, "normal."

Did catch an EPA site stating their survey showed that commercial vehicles are leaking R-134a an average rate of 50% per year and passenger vehicles, 10% per year with a plea, not a law, that the OE's do a little better. EPA is never clear in their statements, don't specify if that 10% leakage us on the full capacity of the system or on the remaining refrigerant left, but I assume they are talking about full system capacity that could add up to 2.4 ounces per year.

Topping off a system is legal, so that is what I do and either by using a sight glass or pressure gauges, monitor that rate of the leak by mostly observing the low side pressure drop at rated conditions. I know around 1994, some of the sight glass readings were not accurate, would always see foam at proper pressures, but believe Honda corrected that. With doors open, AC on, blower at max, and at an ambient temperatures of above 85*F with the engine running at 2,000 rpm, just add refrigerant until you see just a trace of bubbles in the sight glass. Then a couple of weeks later, under the same conditions, just peak at the sight glass to see if you have more bubbles meaning you have a slow leak. If you see foam, you have a major leak and time to repair it or your system may even be empty.

With the EPA stating that 50% is normal leakage for commercial vehicles and 10% per year is normal for passenger cars, all I can say is there is a hell of a lot of R-134a being put into the atmosphere by even brand new vehicles that the EPA isn't doing a damn thing about.

I had to add 12 ounces to my daughters 98 ZX2 last spring, her system failed to kick on, but had pressure in it. Got out my claimed 1/2 ounce per years sensitivity electronic leak detector and didn't find anything. Her system blew cold all summer long, just wrote if off as normal leakage, but would never find that leak or a combination of really small leaks with the most sensitive electronic detector on the market. All MVAC systems leak regardless of how little.

Cussboy on Thu October 29, 2009 3:03 PM User is offline

Quote
Originally posted by: uunfews
For those that use this method for recovery, what percentage of refrigerant were you able to typically recover from the total amount in the system?

I'm a chemist, not an AC Tech. But I do 95% of all my own repairs, and for AC have vacuum pump and gauge set. For me, I estimate 85 - 90% recovery. I've done this three times, all for R-12. I haven't yet had a reason to do a R134a system.

GM Tech on Thu October 29, 2009 5:17 PM User is offline

I started out with dry ice and methanol bath back in late 80s--until I got my first recovery machine in early 90s. Dry ice and weighing the vessel- was always the most accurate method--- I also quit using dry ice in lieu of an immersion cooler. It had a wand that you put directly into the methanol bath along with the pre-weighed vessel. I would always pull the gages down to 24-25 in-hg when all refrigerant was out of system---that's better than some vacuum pumps!! The bath temp was usually at -125 degf--- and it went faster if you heated the a/d with a hairdryer, and ran the blower motor- to warm the cool spots- where the oil would hang onto the refrigerant. A recovery machine will spoil you. I also would use a recycling machine after methanol bath recovery, to clean the refrigerant before re-introduction into a vehicle. With the newest machines- recycling is built into it.

Therefore my answer was that I got 100% of the refrigerant---when the gages read 24 in-hg vacuum!

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Thu October 29, 2009 at 5:19 PM by GM Tech

uunfews on Fri October 30, 2009 6:35 AM User is offline

Thanks everyone for the helpful replies. This is exactly the type of answer I was looking for. With all these wonderful advices and tips I definitely will apply them this weekend to get the rest of the freon out this weekend. I felt that 50psi left in my system was too much pressure from my first recovery attempt and your answers confirm I still have more to go till near empty or fully empty.

My first attempt a 2 weeks ago I got approx 9-10oz. System specs calls for 18.6-19.4oz. I did warm up the engine but didn't closed the hood. Static pressure prior to recovery indicates the correct pressure for that particular day temperature. Also the initial pressure started out at 110psi static and dropped to 50psi static after 20-30minutes of recovery, at which point it stopped w/o any further drop in pressure. I feel I still have plenty of freon left since my compressor is still kicking on except it is no longer blowing cold air as before.


Hope to hear some from others who have tried this method before I try it again this weekend.

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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

NickD on Sat October 31, 2009 8:54 AM User is offline

Don't feel you will get a better response than what you already got from GMtech, but still wonder why you are recovering.

uunfews on Sat October 31, 2009 11:12 PM User is offline

Hi Nick,

To determine if I have an overcharged system is why I am recovering. Last night using plain old ice and salt I got from 55psi to 10psi and recovered an addl 1.9 oz...yea!!! I am out now trying dry ice to see if I can get the last remaining oz out of it or to get a negative pressure reading. Will report back...wish me luck. I know you mentioned about leakage but I got this car second handed so I don't know what was done to the AC if any???? Now if I get a neg reading with so many ounces recovered then I can go from there. System got a rattling/knocking compressor when clutch is engaged on cue everytime. Can't reach below...to tight of a space to get voltage and ohm reading but was able to turn compressor freely by hand and did not see any red heated clutch plate to surmise a possible slippage of the clutch.

Did a performance test but interprating the result using Honda factory service manual's graphical chart was a PITA . I did he best with interpolations graphically and have some indication of an overcharged system but performance test instruction via Honda was questionable and confusing. The instruction called for taking ambient temp by sticking a thermometer next to the blower after accessing via the glovebox. This temperature is different then true ambient temp in the shade. Really messed up manual and confusing to say the least. If i remembered correctly using temp from the glovebox I would be overcharged but temp from outside(in front of the condensor 2") it was in the correct range.

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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

NickD on Sun November 01, 2009 7:04 AM User is offline

Since I am relatively new to AC, really never ran across a system that overcharged itself, what's far more typical is that a system is way undercharged, possibly due to leaks. Feel its very safe to assume, if a system is overcharged, it was done by incompetence and in particular, not watching the high side gauge. Yet another consequence is introducing air into the system, that would really skyrocket the high side readings. Low side may only go up a couple of PSI, with good topping off, but that high side loves to skyrocket quickly.

In a vehicle like a Honda, a very low refrigerant capacity system, overcharging is very critical, once the receiver is saturated, that high side will skyrocket. Typical in production, you can charge strictly by weight and this assumes that the with all the production tolerances, that the unit volume of the system is perfectly identical. With domestic vehicles in particular, the range of low and high side pressures is all over the board and certainly not optimized for the best cooling performance. Japanese do give better PT charts to adjust the charge for optimum values and the same can be done for domestics with skill and care. So I prefer to charge by pressures, but this requires a 85*F day to accomplish this and monitoring the vent temperatures, just one, all others are closed, doors opened, AC on, blower at max, and engine running typically at 1,500 rpm for large engines, 2,000 rpm for the smaller ones. And monitoring the entire system, a peak can be found where adding refrigerant serves to fill the accumulator or receiver, but does not decrease the vent temperature. Granted, far more time consuming than dumping in a precise amount.

Yes, it's nice to have a recharging station where you can extract all the refrigerant into a clear bowl and read precisely the amount you extracted. But if low, the amount of refrigerant lost is only part of the equation, it's also the rate of that loss that has to be considered. Losing say 3 ounces of refrigerant is no big deal if this occurred during a ten year period. But losing that amount the day after a recharge, is a major deal.

In theory, you should only connect your test equipment once to the service ports, each time you connect or disconnect them, either can lose refrigerant or introduce air, the more you play with it, the more you can mess it up, Prefer using valves from that transition between vacuum and charging. Hate cans, because the requires even more fooling around. Do monitor the tank weight, and get the idea if I am dumping in all 30 pounds of a new tank into a 24 ounce system without pressures building up, perhaps something is wrong.

With a charging station, only hook up the ports once, with all valves closed, vacuum out all the connecting lines, then recover and measure how much is left in the system and have the option to add refrigerant to the bowl to the correct amount then dump it back in. Can't do that playing around with cans with constant connecting and disconnecting the ports.

If your compressor is making a racket, more than likely you have already lost valuable lubricant, maybe easy to turn, but only the first sign, it will seize, piston rings or the vane pump is the first to go, bearings will follow. Beating a dead horse here.

uunfews on Wed November 04, 2009 5:41 AM User is offline

Quote
Originally posted by: NickD
Since I am relatively new to AC, really never ran across a system that overcharged itself, what's far more typical is that a system is way undercharged, possibly due to leaks. Feel its very safe to assume, if a system is overcharged, it was done by incompetence and in particular, not watching the high side gauge. Yet another consequence is introducing air into the system, that would really skyrocket the high side readings. Low side may only go up a couple of PSI, with good topping off, but that high side loves to skyrocket quickly..

My hi was just slightly high (if I was measuring ambient temp from glove box instead of front of condensor) so I figure it wasn't from the air.


Quote

In a vehicle like a Honda, a very low refrigerant capacity system, overcharging is very critical, once the receiver is saturated, that high side will skyrocket. Typical in production, you can charge strictly by weight and this assumes that the with all the production tolerances, that the unit volume of the system is perfectly identical. With domestic vehicles in particular, the range of low and high side pressures is all over the board and certainly not optimized for the best cooling performance. Japanese do give better PT charts to adjust the charge for optimum values and the same can be done for domestics with skill and care. So I prefer to charge by pressures, but this requires a 85*F day to accomplish this and monitoring the vent temperatures, just one, all others are closed, doors opened, AC on, blower at max, and engine running typically at 1,500 rpm for large engines, 2,000 rpm for the smaller ones. And monitoring the entire system, a peak can be found where adding refrigerant serves to fill the accumulator or receiver, but does not decrease the vent temperature. Granted, far more time consuming than dumping in a precise amount.

Yes, it's nice to have a recharging station where you can extract all the refrigerant into a clear bowl and read precisely the amount you extracted. But if low, the amount of refrigerant lost is only part of the equation, it's also the rate of that loss that has to be considered. Losing say 3 ounces of refrigerant is no big deal if this occurred during a ten year period. But losing that amount the day after a recharge, is a major deal.


I followed up the ice/salt bath with dry ice but I couldnt get any further extraction. Pressure remained the same even with a warmed up car and evaporator and the use of a heat gun on lines and dryer. When I bled the remainder all I got was a tiny whoosing sound which lead me to think the amount left was insufficient for the dryice to do any further recovery.


Quote


In theory, you should only connect your test equipment once to the service ports, each time you connect or disconnect them, either can lose refrigerant or introduce air, the more you play with it, the more you can mess it up, Prefer using valves from that transition between vacuum and charging. Hate cans, because the requires even more fooling around. Do monitor the tank weight, and get the idea if I am dumping in all 30 pounds of a new tank into a 24 ounce system without pressures building up, perhaps something is wrong.


I measured this lost to be approx 3-5gram of trapped refrigerant inside the gauge. So connecting/reconnecting a gauge 5-6 times would equate to approx 1 oz lost.

I would use a 30lb tank also except I think it would be difficult to find a digital scale with good accuracy, meaning one with low sensitivity value.

Quote

With a charging station, only hook up the ports once, with all valves closed, vacuum out all the connecting lines, then recover and measure how much is left in the system and have the option to add refrigerant to the bowl to the correct amount then dump it back in. Can't do that playing around with cans with constant connecting and disconnecting the ports.
Wish I have a charging station but out of budget for a DIYer. But definitely will use the charging station the next time around.


Quote

If your compressor is making a racket, more than likely you have already lost valuable lubricant, maybe easy to turn, but only the first sign, it will seize, piston rings or the vane pump is the first to go, bearings will follow. Beating a dead horse here.

I have the compresor out now and there is definitely no noise made when turning it by hand. Clutch looks good. I also rechecked the mounting bracket with a torque wrench thinking that it might be loose but no indication of that either. Maybe it was lacking oil. Or maybe the noise only happens under faster rpm then what my hand is capable of producing. Any recommendation you can think of where I can duplicate the noise out of the car to confirm if I really have a damaged compressor. Hate to chuck good compressor if the cause of the noise was due to the lack of oil perhaps????

Additionally, my drained oil from the compressor is clear amber yellow with no metal flakes which is kind of odd . I was expecting some wear metal and burnt oil.



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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

Edited: Wed November 04, 2009 at 6:00 AM by uunfews

NickD on Wed November 04, 2009 11:04 AM User is offline

Little confusing about the drive belt system on your vehicle, seems like a lone belt is used for the PS pump with another for the alternator, AC compressor, and more than likely idler and tensioner pulleys. Recall an older Honda where the damper pulley was next to falling off. Point is, when your compressor is on, puts a strong load on your belt system, good to check all that out. The ball bearings in the alternator are of the sealed limited lubrication type, grease dries and also makes a racket, augmented by the severe load the compressor when on puts on it.

uunfews on Wed November 04, 2009 2:50 PM User is offline

You are correct Nick. There are two drive belts. One to drive strictly the P/S Pump . The second belt drives the AC Compressor and the Alternator. I spun the pulley of the Alternator and it spuns freely several revolutions with no racket. There is no idler, tensioner or dampener pulley system whatsoever on this model year.

Don't forget coolant got to be Honda also. But you are right I hate Honda for their fluid requirement. This is my first and will be my last Honda. They use cheap components whereas with Toyota it is of better quality. I have never seen a Toyota compressor making any racket when the AC stops working. But I have seen first hand with my car and from seing/hearing from others.

What is MVAC fluid? You mean the oil like Sanden SP-XXX oil and refrigerant?

Speaking of which, would you use Honda's AC Orings or should I use the aftermarket Santech branded orings?

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Newbie wanting to learn how to fix his 01 Civic AC in this freaking hot Dallas TX area.

Edited: Wed November 04, 2009 at 3:28 PM by uunfews

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