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  #1  
Old 06-22-2006, 11:50 PM
deniss's Avatar
'84 300SD W126/OM617
 
Join Date: Apr 2006
Location: Central NJ, USA
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adding R-12 to AC system on 300SD

I was looking at some kits on eBay for adding some R-12 to my system. It definitely needs a charge because now that it's hot, the air isn't blowing cold anymore.

There are various kits on eBay that sell 12-oz R-12 cans along with a can of oil for R-12 systems. They include the can tap with a hose that ends with a schroeder valve. Some kits also have a pressure gauge.

A few questions:

1) how much of that oil should I put into the system?
2) some kits sell a pressure gauge inline with the filling hose. which pressure readings am i looking for to know that the system has enough R-12 added?
3) the instructions say to use a low-side port for filling. i've been told that on the 300SD, the low-side port is located up front behind the grille next to the radiator... can someone verify that please? there's another port that's by the firewall - is that the high-side service port?

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  #2  
Old 06-22-2006, 11:57 PM
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Join Date: May 2005
Posts: 992
r-12

yes, they do sell r-12 on ebay but you must send them a copy of your
hvac lisences. So you have done all that.
Yes, there is an online lisence system.


If you have not then look into freeze 12. or Ev 12. These do not require the
lisence. dieselgiant has the freeze 12... it works well.
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  #3  
Old 06-23-2006, 12:03 AM
deniss's Avatar
'84 300SD W126/OM617
 
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Location: Central NJ, USA
Posts: 452
I do have the license for buying R-12 and I'd like to stick to it for now.
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  #4  
Old 06-23-2006, 08:05 AM
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Location: central Texas
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Deniss, I do not understand how you could have a license and still have such basic questions about AC... I suspect you have ' access' to someone with a license who will help you buy it .... (?)
You need to go to aircondition.com and read their ' knowledge base' section.
Your basic assumption about the hot air and low R-12 is faulty. There are all sorts of other things which can cause that symptom... but even if it is low you need to address WHY it got low before dealing with the charging side of the equation...

Last edited by Brian Carlton; 07-06-2006 at 09:26 PM.
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  #5  
Old 06-23-2006, 08:33 AM
deniss's Avatar
'84 300SD W126/OM617
 
Join Date: Apr 2006
Location: Central NJ, USA
Posts: 452
No, I *do* have an EPA Section 609 cert from MACS - not using someone else's license. Have you taken their certification test? If you did, you would know that it doesn't really teach you much about the actual service, just outlines some safety and environmental concerns and outlines some basics about refrigerant recovery and recycling. It doesn't teach you to be an AC tech.

Now, moving past my license/certification and my lack of knowledge in the field of automotive air conditioning...

What can be some of the things that might cause the AC system to not produce cool air, other than the lack of refrigerant?
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  #6  
Old 06-23-2006, 08:45 AM
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Aircondition.com is used as a reference by all sorts of persons including professionals...
If you had run over and scoped it out you would realise they have already presented the answers to your question way better than anyone on this site can.

The Aircondition.com 'knowledge base' section can't be beat...

You must stick guages on both sides of the system and stick a thermometer into the center vent and turn on the system for at least ten minutes outside but not in the sunshine to establish anything in terms of a base line to start from.
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  #7  
Old 06-23-2006, 08:51 AM
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Location: Deltona, Florida
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Hey,
Your question #1 is the key to your answer. There is no way to know how much oil to add because you have no way of knowing how much oil is left in the system.
I don't think I need to tell you what the lack of oil will do to your compressor and adding too much oil is just as bad.

The proper way to fix it would be to find the leak, fix it, flush the system, pull a vacuum and recharge with the proper amount of oil and refrigerant.

What you can do is put some R-12 in and look for the leak. When the charge gets low again that it doesn't work then you can go on to making the proper repairs.

Danny
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  #8  
Old 06-23-2006, 09:13 AM
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Deniss, your ac system has been opened up to replace hoses ... right ?

So this statement in the first post "for adding some R-12 to my system." was intentionally misleading...

It does explain how you knew for sure it was needing refrigerant as compared to the other things which had not been ruled out first...

How do you expect to get good answers if you are not honest about the situation ?

Last edited by leathermang; 06-23-2006 at 09:27 AM.
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  #9  
Old 06-23-2006, 10:26 AM
deniss's Avatar
'84 300SD W126/OM617
 
Join Date: Apr 2006
Location: Central NJ, USA
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Don't be so quick, please, in questioning my honesty. I take that seriously but will disregard that comment.

Since we're getting deeper into the subject than simply adding refrigerant, I will tell you what I know about the history of my AC system, which isn't much. I don't pretend to know much about AC systems (as is obvious from my basic questions), and I'm not trying to hide anything. I'm just trying to find an economical way to getting cooler air out of my air vents...

The AC system has not been opened during my ownership of the car, which has been just over 2 months now. I personally didn't touch the AC system or requested any repairs made so far. When I bought the car from the previous owner, it was April, and it was moderately warm outside, and at that time, the AC system was producing cool air. It wasn't cold, but it was cool enough to chill the interior - I didn't measure the temperature.

Now that it's gotten hot out, the system cannot keep up. It delivers sort of room-temperature air (cooler than outside air, but not cold enough to have any effect on cooling the interior). The previous owner told me that the AC system "could certainly perform better - might need a charge of Freon". I haven't used the AC since it's gotten hot out because it's useless to run it when it doesn't do anything for me.

Since I've never serviced an AC system, I blindly assumed that it must need more refrigerant. I didn't know about that website - thanks for pointing it out; I will read it. I had concerns about adding oil. I do know that too little or too much oil are both bad, so that was the reason for asking question #1. I guess there isn't an easy way to answer that question without evacuating the system completely and doing a fresh fill.

I understand that the proper procedure would be to leak-test and, if there is a leak, to recover the refrigerant, fix the leak, flush, evacuate, and refill, but certainly I don't have the equipment to do that, nor do I pretend to have any knowledge about carrying out that procedure properly.

However, even with my lack of knowledge and equipment, couldn't I start the diagnostic process by measuring the pressure at the low-side port? If it's low, I guess that would point to a leak, and if it's normal, I guess it would point to something else. I've seen a couple tester gauges at autoparts stores for measuring the refrigerant pressure in the system. Couldn't I do that first and go from there?

And cut the newbie a little slack, will ya please? Just trying to learn, like everyone else
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  #10  
Old 06-23-2006, 11:29 AM
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"Since we're getting deeper into the subject than simply adding refrigerant,"

Your system was opened up to replace hoses ... is that correct ?
If yes.... and you know I am not psychic...that there is a reason I think this... then you were past " simply adding refrigerant" before you starting typing the first post...

Since you are at that stage you need to consider flushing your system... you really need to read all you can on the Aircondition.com site first to understand the basics of AC theory...... then come over here to ask questions specific to your car and MercedesBenz....

Another thing is that there are MOUNTAINS of posts in threads already on this site.... a bunch of the posts in them are me trying to convince people to follow the rules of physics and proven techniques for long lasting good working AC systems...

Putting the right amount of oil into a system is a big problem for everyone.. lots has been written by me and Larry Bible about that...

The safe way is to flush the system and measure clean new oil into it when you charge it up with refrigerant.

Have you read any other threads on this site about AC recharging or fixing ?
Until you understand the basic theory you will not understand why you can't jump to the end of the process and your AC fix be successful...
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  #11  
Old 06-23-2006, 12:00 PM
deniss's Avatar
'84 300SD W126/OM617
 
Join Date: Apr 2006
Location: Central NJ, USA
Posts: 452
Quote:
Originally Posted by leathermang
Your system was opened up to replace hoses ... is that correct?
As I was just saying in the previous post, I can only tell you that during MY ownership of the vehicle (last 2 months), the AC system was NOT opened. The previous owner told me that he has done no work on the AC system either. The hoses don't look like they have been recently replaced, but the whole set-up looks quite clean from the visual inspection - no oil residues that I found so far.

I did ask a question specific to my car. Which is the low-side service port? Is it the one by the radiator up front behind the grille? That's what I've been told, but I want to confirm that.

So can I or can I not measure the pressure at the low-side service port with a tester gauge to find out whether refrigerant needs to be added?
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  #12  
Old 06-23-2006, 12:00 PM
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Putting gauges on it would be a good place to start.
Maybe Autozone has them in their rental program?

The easiest way to find a leak is to look for oil. When refrigerant leaks oil leaks out too. On a pressurized system you can use soapy water. Or some kind of leak detector. Click here
Click Here

You will also need new o-rings, nylog, a vacuum pump, refrigerant and the proper type of oil. Not to mention a new receiver/dryer and any other parts that may be needed to fix the leak.

Danny
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  #13  
Old 06-23-2006, 12:57 PM
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"The easiest way to find a leak is to look for oil."

Yes, but that does not work if the PO or you have done a good job of cleaning the engine compartment... not uncommon when preparing to sell a car...

Soapy water also does not work if the leak is above a certain size because it blows out the bubbles instead of making them..

"I did ask a question specific to my car. Which is the low-side service port? "

You asked a specific question without knowing enough about AC theory. It is dangerous to not know by looking which is the high pressure and low pressure lines.. the refrigerant can could blow up in your face... literally...
Aircondition.com knowledge base will tell you how to recognize which is which on ANY vechicle...
What if someone changed out your condensor or stuff and what we would describe as the usual stock place for the low port is where you find a high port ? Then you get hurt or mess up your system by doing something like installing your refrigerant in liquid form and breaking your reed valves in your AC... there are too many variables for you to start doing stuff before you learn more about the theory of AC operation.
Go to Aircontion.com and read everything you can find there... then you may be ready to address Your car safely...
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  #14  
Old 06-23-2006, 02:50 PM
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R12

in Norway u aint alowed to use R12 anymore :-( so everybody use R134
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  #15  
Old 06-23-2006, 03:03 PM
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In Norway you don't ever have the blistering heat that occurs in Texas for months at a time....

All the vehicles on this 30 acres have 134a except my 1980 Mercedes...
Honda, Ford, Lincoln... all plenty cold.. but made to use 134a...

I have no argument with people using 134a... and I may upgrade my condensor, compressor and reciever dryer and go with that in my Mercedes....

But I try to warn people about using blends like Freeze12 for all the reasons which have been stated before..

There exists a certain amount of R-12 right now ( 7- 12 ounce cans in my storage area )... what would you suggest be done with that ?
Burn it and make phosgene gas ? Store it without installing it until the cans rust and leak it out ? Or follow the rules and use it in the car until the car wears out ?

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