All,
Have any of you done a recharge on your A/C unit? Mine seem to have run out and needs to be charged. If you've done it, do you recommend using one of the kits available at an auto-part store (Murray's, AutoZone, etc.) or have it done by a pro? I've been told the kits are pretty easy to use so I would like to learn to do it myself. Thanks for any help.
- Thee Chicago Wolf
To do it right, you need to start from scratch, which means you need a good set of gauges and know how to use them. You also need a vacuum pump to hook up to the system, which will cost you about $400 or so. You really do need to know the procedure so get a shop manual for the car. If you do it wrong, and open up the high pressure side to the can of freon, you're dead! It's really not that hard but you just need to know the steps and precautions.
"Tom" wrote in news:5oRCg.4515$ snipped-for-privacy@bignews2.bellsouth.net:
Sorry, but you don't need a vacuum pump. If you have good gauges, hooked up to the right ports, know the ambient air temp., and how much charge the system is supposed to have, you can fill the system properly without a problem.
Eric
You need a good sensitive refrigerant scale. Virtually all automotive AC systems are charged by weight, not pressure/temperature.
gerry
gerry wrote in news: snipped-for-privacy@4ax.com:
From the factory, yes. In the field, it can actually be better to use pressure/temperature. What do you propose? Evacuate the entire system and add X ounces of refrigerant?
I believe that is the correct way to do it. That obviously isn't what happens with the DIY kits.
Matt
Matt Whiting wrote in news:9a6Dg.457$ snipped-for-privacy@news1.epix.net:
Absolutely, it is the right way to do it. We were talking about DIY from the start, or so I thought. Although gauges can cost hundreds of dollars, you can usually find someone that will let you borrow a set, and then you can just use a can of R-134a from an auto supply.
Eric
You might not need a vacuum pump for your AC service, but I sure do.
Of course, I like my AC cold and my pumps happy and long lasting. Iced up orifice tubes suck.
JS
Weigh in is the ONLY proper way!!! That is also why legal recharging places have recovery/recycle equipment. In the US, the EPA actually requires 609 certification to work on MVAC equipment such as an automobile. "Recharge kits" exist because R-141a does not need a certification to purchase and the EPA overlooks the private usage.
Weigh-in is the only way to get a full charge without overcharging!
Automotive systems use an accumulator or receiver and TXV metering. Since this setup keeps a reserve of liquid, the amount of reserve can not be determined via pressure. Too little and you will get less than desired capacity. Too much and you get liquid in the compressor and destroy it. Pressure remains the same without regard to liquid level in the receiver or accumulator.
gerry
Automotive AC's don't use orifice tubes, they use TXV's for metering.
gerry
Aftermarket freon refill kits should BE BANNED. They are dangerous in the hands of the inexperienced. Further, the average consumer doesnt have the knowledge on how to properly recharge an auto a/c , doesnt have the tools/guages nor knows how to read them and understand the relationship between pressure and temperature of R134 , will most likely end up putting air as well as freon into the system and eventually causing problems , etc.... Spend the money and have a professional do it --- dont go to your local Oil Change place either...go to a proper Service Station or the Dealership you bought the car from . If you are constantly adding freon to your system, have it electronically leak checked during your recharge visit.
'Sorry, but you don't need a vacuum pump. If you have good gauges, hooked up to the right ports, know the ambient air temp., and how much charge the system is supposed to have, you can fill the system properly without a problem. Eric '
REPLY: If the system is totally empty, you WILL need a vaccuum pump to rid the system of air and moisture and do it correctly. Further, you dont 'fill' an auto a/c system (to the top) ; it has to be accurately metered in and depends on a variety of factors . You will NOT know how much freon to put in unless you weigh in the EXACT amount which requires a Charging Cylinder that is marked off in lbs and ounce increments .. which requires you to know how to use it properly ; if y ou just add freon from a store bought kit , you are only guessing . If youre a consumer, stay away from touching your a/c system except to power wash your Condensor Coil routinely.
In older a/c systems, the manufacturer used to include a sight glass for recharging ; you hardly ever see this on systems any more. One would simply add freon thru the low side until the high side sight glass was clear of bubbles. Without this sight glass on the system, you must accurately weigh in the freon charge using an accurate clear Charging Cylinder with graduation markings on the side ; something that is not available to the public. To not use this method, is only guessing at the charge you have put in.
Actually, recharging an automotive AC does require at least EPA 609 certification. USING the kits without such is illegal in the US.
Purchasing R-134a does not require certification since it has many uses other than as a refrigerant and is not an EPA controlled material.
As stated elsewhere in this thread, 609 is rarely enforced for private usage.
gerry
Typo above, "R-141a" should read "R-134a"
gerry
Actually, if the system has stood without pressure and a leak, chances are the hygroscopic PAG or POE oil has been permanently contaminated. Drain, flush and changing the dryer is the only way to get the acid that forms when moisture hits the R-134 compatible oils out.
Old R-12 systems used mineral oil that was not affected by moisture.
gerry
'Actually, recharging an automotive AC does require at least EPA 609 certification. USING the kits without such is illegal in the US.'
REPLY: I was going to mention this fact, but, R134 is too readily available to the consumer and abiding by Government Laws is going to be the least of their concern.
'Actually, if the system has stood without pressure and a leak, chances are the hygroscopic PAG or POE oil has been permanently contaminated. Drain, flush and changing the dryer is the only way to get the acid that forms when moisture hits the R-134 compatible oils out.'
REPLY: Correct. And you still need the Vaccuum Pump for pulling a deep vaccuum once the system is cleaned up .
Matt is correct. The proper way is to evacuate the system WITH A VACUUM PUMP and recharge it with the correct weight of freon. I believe that you said that the system wouldn't work at all which indicates that the freon level was so low that the pressure switch was not making. At that point, you have to assume that the system is empty and probably has air (with moisture) in it. At that point, you have to use a vacuum. I know I say that because I'm lucky enough to have one from where I used to work, but I also know that it's a big outlay of money and you would want a cheaper cure. I guess you could just recharge it and hope for the best but it won't cool as well because you won't have the same amount of freon in it, or, if you put the right amount of freon in it, then you've over charged it with the air already in there and you could blow hoses, seals, etc.
And if it is empty, then it has a leak. One needs to find the leak before recharging the system. Most DIYers aren't capable of doing that either. I like working on my car as much as the next guy, but some jobs just require more tools that I care to buy in order to do the job right. Most AC work falls into that category.
Matt
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