Auto A/C

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  #1  
Old 05-25-02, 11:45 PM
smj5169
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Auto A/C

Yes I have a 97 VW cabrio and the A/C is not cooling good. Where I get my oil change they checked freon and said it was a little low. They just won't add a little they want to drain all the freon out and fill all the way back up and charge me 150 dollars. My question I have the valve to hook on to the R134a freon can and add some but can you add to much and harm system. I have been told if you just add one can that it will go in and if it get's full it will quit going in. I also have one of the guages that has 4 different colors for freon level you buy at auto store for under 10 bucks are they accurate? Thanks for any help or suggestion. Steve
 
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Old 05-26-02, 07:33 AM
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I'll let the pro's speak to the technical specifics, by my 2 cents worth on your post is that I would avoid like the plague any shop that suggested a complete drain and fill of freon for a slight undercharge condition unless there's some type of repair or further troubleshooting involved. What they could possibly be doing (other than getting their $5000 freon servicing/recycling machine paid off sooner) to earn $150 would be a mystery to me. Did they give you some technical reason for the $100 overkill? That's about 30 minutes labor and $10 worth of freon job. Maybe you're in an area where ac work commands those kinds of prices. Here in SW Fla there's an ac shop on every other corner and they will all check your system for free and to top off the charge is maybe $20 (unless it's R-12).
 
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Old 05-26-02, 07:46 AM
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smj5169:
You cannot add refrigerant to a system without being able to see what's going on in the system. You need to have guages on both the low and high pressure sides to be able to diagnose a low refrigerant condition. Adding refrigerant without knowing the high side pressure could cause an overcharge and either damage your compressor or cause something to break.
The reason they may want to remove the complete charge is that they may not have the technical expertise to be able to just add refrigerant based on operating conditions. This would mean they have to know what is going on in the system and how it works.

Keep in mind though that the leak still must be found. Depending on where the leak is you still may have to have the refrigerant removed to make the repair.
 
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Old 05-26-02, 09:34 AM
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a/c

Most modern automotive a/c systems are known as critical charge systems.So what this means is 1/4 lbs either way it mat not work properly.Because of this you need guages and have to add refrigerant slowly and give the system time to stabilize,the other option is to dump the system charge into a recycling machine and charge from the beginning.Doing it this way your charge would be the most accurate,however why should they charge you for r134 they recovered from your system?You may have a leak or restriction in the system or possibly a tired compressor,without guage readinds you can not tell.If you never had it serviced you could be down 1/4 to 1/2 pound because r134 leaks more readily than r12 ever did to its small molecules,where you have a small r134 leak you will not see oil or uv dye with r12 you get oil stains.Pag oil molecules are larger than 134 molecules so you won't see oil stains unless you have a large leak.I would have someone else check it for you.It will be hot soon.
 
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Old 05-26-02, 12:38 PM
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Thumbs up Critical charge.

davo:
You are absolutely correct about the critical charge.
I gave up auto A/C when the cost of converting older vehicles sometimes exceeded the value of the vehicle.
I'm curious to know what most auto A/C shops would charge when removing and replacing the refrigerant charge.
My thinking is that charging for the refrigerant would be reasonable given the cost of the A/C tools and equipment.
In commercial refrigeration the quantities are considerably larger and the refrigerants are 2-3 times the cost of R-134A, so we generally charge a service charge to cover the cost of the equipment.
What do you guys do?
 
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Old 05-26-02, 05:52 PM
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With the newer generation of recovery and servicing machines the cost of freon to service a slight undercharge or to refill a system that was drained for troubleshooting and repair is fairly low since the recovered freon is reused. And the labor involved is pretty minimal, also, since the machines are quite automated - couple of minutes to hook up, push a few buttons and go do something else while the machine works. The real cost involved is for the overhead of the cost of the machines themselves. As I recall the latest ac servicing unit our favorite garage has in use ran into several thousand dollars. Kind of like the guy I tow in who breaks down 2 blocks from his mechanic and thinks the charge should be lower - I still have to write that $7k annual insurance check regardless of how far we tow the vehicles.
 
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