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Discussion Starter · #1 ·
This summer, Im taking a class in automotive air conditioning and heating. I talked to the instructor and we decided to bring my rig in for some work. The past few weeks, the AC has been very weak. So, we brought the car in the shop and checked things out. Come to find out, my car was reading extreamly high when the car was not running. With it running, the cold side was within spec. The high side was very low.

Next thing to do was to determine what refridgerent was used (R134a for those interested) and we evacuated the whole system. Nice thing to know is that the oil in the system is also equipped with a leak detection device. So, when you evacuate the system (take the car to a shop for this repair) you will need to add the leak solvent again. So, if you have a leak and you see yellow goo around any fittings, you are sure to find out that the AC system has a leak in it. Once all cleaned out, we loosed the hard line coming out of the passenger compartment.

The thin hard line from the passenger compartment to the engine will have a small crease around the line. This is where the oriface tube is. This device is a pressure device that keeps the fluid under a consistant pressure. It also acts as a filter for the fluid. My tube was black and yellow. The yellow was from the leak detection fluid, and the black stuff was oil and rubber parts from the compressor. These signs are the beginnings of a compressor failure. For the amount of miliage on my car (106,000+) its within specs. Luckily, the shop at school had some spare tubes (over a 2 lb bag of parts) that was the same exact size, type, and everything for the original part. Its amazing... a school that mainly has cars from GM, Ford, and Dodge actually had the part for a VOLKSWAGEN. :D

Got the car all back together and fully recharged. What a great feeling it was to have ice cold AC again. Before, I had to wait atleast 15-20 mins for mediocurly cooled air. Now, its within minutes. I cant complain. The whole repair was free, and I learned more about my car.

So, if you have a poorly operating AC system this summer, let this be one of the 1st things to check.

HTH,
Steve
 

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For the amount of miliage on my car (106,000+) its within specs.
Within spec? What the hell does that mean? :p Is an A/C compressor one of those wear items that Volkswagen doesn't tell us about? :lol:
 

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Scuba2001 said:
The thin hard line from the passenger compartment to the engine will have a small crease around the line. This is where the oriface tube is. This device is a pressure device that keeps the fluid under a consistant pressure. It also acts as a filter for the fluid.
I just worked on my own AC, but aren't sure what you're referring to here. Got any pics?
 

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Any kind of self-maintenance us shade tree guys can do?
My car is a '00, and I was thinking maybe I can recharge the system myself...???

:thumbup:
 

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Discussion Starter · #7 ·
AidanLee said:
I just worked on my own AC, but aren't sure what you're referring to here. Got any pics?
Yeah, Ill snap some pictures tonight.

Self maintenence... No. This is better left to the professionals. Refridgerent is very dangerous at such high temps. This stull boils at -15 degress or so, so when you go messing with it, you can get seriously injured if you dont know what you are doing.

Steve
 

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Oh, didn't go near the refrigerant myself. Had a shop evac and then later recharge the system so I could replace the evaporator. Check out the post in the Info forum to see what I went through.

update: oh, didn't notice you were responding to two people in your post. my bad :oops:

yeah, what Steve said. leave the refrigerant to professionals. ripping the dash apart on the other hand, is quite the experience
 

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stealthx32 said:
For the amount of miliage on my car (106,000+) its within specs.
Within spec? What the hell does that mean? :p Is an A/C compressor one of those wear items that Volkswagen doesn't tell us about? :lol:
again, "within spec"? Should we be expecting compressor failure, or simply having our systems charged? anything preventative, proactive, etc that is suggested?

thanks for the info.
 

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Discussion Starter · #10 ·
99blackmagic said:
again, "within spec"? Should we be expecting compressor failure, or simply having our systems charged? anything preventative, proactive, etc that is suggested?

thanks for the info.
Im just suggesting this as a proactive thing. If you can sense that the ac is getting warmer, more then likely its a blockage in the system, hence my suggestion to get this checked. Its better then having it checked by a dealer who may diagnose it as a complete compressor repair/replace that isnt totally needed at this point.

Steve
 

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Scuba2001 said:
AidanLee said:
I just worked on my own AC, but aren't sure what you're referring to here. Got any pics?
Yeah, Ill snap some pictures tonight.

Self maintenence... No. This is better left to the professionals. Refridgerent is very dangerous at such high temps. This stull boils at -15 degress or so, so when you go messing with it, you can get seriously injured if you dont know what you are doing.

Steve
I'm not doubting it's potential to be very dangerous.
But then I wonder why they would sell kits like this one readily available at J.C. Whitney, and they claim "comes with detailed instructions", so you know the average schmo is using it.

http://www.jcwhitney.com/webapp/wcs...ductId=3967&TID=101&catalogId=10101&langId=-1

But if you really think it's better left to the pro's then I'll take your word for it.

Thanks! 8) [/i]
 

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Discussion Starter · #12 ·
Yeah, the average person can do it. Evacuationg the stuff is the important part. Recharging the system is more indepth. And, to remove all air, its best to pull a vacuum on the system before you recharge so no moisture is in the lines.

Just my personal exerperience, thats all.

Steve
 

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Uhmmm, that's a really fast reply!
( yeah, and I'm not working right now. 8) )

OK, so one of the most important parts of recharging the system includes "evacuating" the system too, right? And do you think this kit (or other kits like this one for that matter) doesn't do this? Because if so, it's sounding more like like something I might rather have a pro do.

But I'm a little confused, is the AC system something you would maintain by topping off with refrigerant/oil, and not necessarily evacuate?

Or is the AC system something you just have maintained on say a 2-3 year basis. Oooor rather a "full service" frig/oil/evac performed when you notice the AC not performing up to snuff after let's say 5 years? Because if it's the latter I'm leaning towards just let a pro handle it.

Y'now I'm thinking auto manufacturers might handle it like one of those "lifetime-never-needs-service" things. Sorta like VW put on their auto tranny's, and you wind up with a new tranny eventually!

Thanks. :)
 

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Discussion Starter · #14 ·
OK, here is a crash course in AC systems.

Your AC is a SEALED unit. It does not evaporate into thin air at all. It goes from a high pressure gas to a high pressure liquid coming out of the condensor (the part in front of the radiator) and then goes back into the oriface tube, into the evaporator (which absorbs heat from the passenger compartment, into the accumulator and then back into the compressor. I may have this switched around a little, Im still new to this. My books are in the car.

So, passing through the evaportator and the condensor, this changes the state of the refridgerant from gas, liquid, etc. The standard psi under operating temps on the high side of the compressor is 223 psi. Thats extreamly high, not something that I personally would want to attempt without the correct equipment.

The items listed you have above is basicly a for someone just wanting to avoid a costly repir due to a leak. For someone that just wants to recharge the AC and not be bothered with a small leaky hose.. that kit is perfect. The system in the Passats are already equipped with a leak detector which is a yellow dye. So, if you have any fittings that have a yellow film around them, you have a leak. The items above... they cannot recover any refridgerant from the car, just to recharge it.

Dont mess with it if you dont know what you are doing. Many have been injured, even technicians, who dont pay attention to this. I did all of this work at school, so we had all of the right stuff to do it right the 1st time.

Steve
 

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My Dad was a service station owner (Service Stations - remember those?) and he was very good with A/C stuff. Having grown up working for him, I'm pretty handy with a wrench. I still have his gauges (for filling), but he got rid of his vacuum pump (dammit!) But unless I have to, I don't mess with A/C, for the reasons described above. The trick is to find a tech who's truly knowledgable so that if there is a problem, it can be quickly and correctly diagnosed w/o a lot of expensive part-swapping. Sounds like Steve is getting there... :wink: :thumbup:
 

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Scuba2001 said:
The standard psi under operating temps on the high side of the compressor is 223 psi.
Not to bug you or anything, just want to put in some notes :) never know, may be helpful in the future.. but I'm also going on pure memory here, as you are so I might be off on some..

**

at 80 degrees with the compressor on, low side pressure should typically be between ~30 and ~45 - high side pressure should be between ~125 and 225.. In the real world, (not theoretically..) if there's an AC problem that the numbers aren't proving.. 225 PSI would be considered normal to high..
When the compressor is off the pressures equalize


"With it running, the cold side was within spec. The high side was very low."
If the compressor cyle time is fast, it's on and off very short amounts of time - this does indeed often mean low charge :D

"Next thing to do was to determine what refridgerent was used (R134a for those interested)"
As far as I know, every passenger car since 1995 uses this as a mandatory regulation.. Then again I work on fords, so I can't speak for every single automaker..

"Your AC is a SEALED unit. It does not evaporate into thin air at all. It goes from a high pressure gas to a high pressure liquid coming out of the condensor (the part in front of the radiator) and then goes back into the oriface tube, into the evaporator (which absorbs heat from the passenger compartment, into the accumulator and then back into the compressor. I may have this switched around a little, Im still new to this. My books are in the car.
"

correct, it is not supposed to evaporate..


From the compressor, you have a high temp, high pressure vapor line into the condenser, the condenser condenses the gas into a liquid, and cools it (evaporating/condensing happens much more quickly under the pressures an AC system is under..)- from the condenser you have high pressure/low temp liquid
Fixed orifice tube acts as a restriction, changing the now low temperature, high pressure liquid to low temp, low pressure liquid, from there into the

Evaporator, which basically absorbs the heat of the passenger compartment, while turning into a vapor (inside the evaporator) from the evaporator it goes to the accumulator/drier.. which is close to engine heat, to better turn any liquids left into gas, and the dessicant in the accumulator/drier absorbs any leftover liquid before moving back to the compressor, it's now a low pressure, low temp gas..

Then the cycle repeats

hope I haven't confused anyone.. :)

On a side note : R134A systems use quick disconnects as the access to the system, the low side (usually matched with blue connectors for equipment/gauges) is smaller and near the accumulator/drier the high side is usually located closer to the condenser, and is matched to red, at least in fords' world..

"Next thing to do was to determine what refridgerent was used (R134a for those interested) and we evacuated the whole system. Nice thing to know is that the oil in the system is also equipped with a leak detection device."

Typically its a yellow dye, used to find obvious and not so obvious leaks ..
If you're low on fluid but don't see any obvious leaks, use a blacklight and specific yellowed glasses to check for any signs, the UV light helps big time on the small leaks :)
 

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yeah i took an a/c course last year, interesting stuff, learned alot. :thumbup:
 

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Just a couple of points for those who are interested:

The purpose of evacuating a system is to: 1) check for leaks by isolating the system from the vacuum pump and see if it holds a vacuum, and 2) to evaporate any water in the system. Water is not a friend of a working AC system because it does not have the correct properties for the heat cycle as the freon does. Water at room tempature boils at low vacuum (as in 1 or 2 psia) and is removed by the vacuum pump when a system is evacuated.

In the older designed systems (and some modern systems), there was a sight glass on the liquid leg that you could use to tell if the charge in the system was low or not. And also you could use it to safely add freon without adding too much (add until the gass bubbles disappear). Our cars do not have a sight glass. The only way to really measure for full charge is to completely evacuate the system and then to charge it with the correct weight of freon by weigthing the freon bottle as it is being added.

By using a set of gages, you can get an indication that the freon charge is low and you can added some using one of those kits they sell at auto supply stores. These are usually only good if your problem is caused by a low charge from normal leakage or a very, very slow leak. If the reason the system is not performing is other than that, the repair is best left to the pros as the equipment needed is very specialized and expensive.

Regards, Ray
 
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