What's the proper procedure for adding R12 refrigerant?

-
cudajim

cudajim

cudajim
Joined
Jan 17, 2006
Messages
1,486
Reaction score
102
Location
Grass Valley, Ca.
I have a few cans of the ever-so-rare R-12 refrigerant left over and I want to add it to my 69 Barracuda. What is the proper way to do this? I have the proper old R-12 hose but no pressure meter attached to it. I have heard some people say keep the can upright while others say tip it upside down... both cannot be right. When I charge my 94 Dodge van every (yes it leaks slowly) I use R134 and turn it upside down which always works. Thanks.
 
This will help you Im sure its the same way as the 134 stuff.... to much will shut down compressor. Could be wrong however.

[ame="http://www.youtube.com/watch?v=ERDsfRRMuow"]YouTube - ‪Car Maintenance : How to Add Freon to a Car Air Conditioner‬‏[/ame]
 
Well both CAN be right--just depends on the situation and your experience.

The DANGER is that with the can upside down you are feeding in LIQUID, and piston pumps do NOT like liquid in the cylinders and valves. So if you feed in too much too fast you can "slug" the compressor. You might get to hear what a breaking rod sounds like.

The SAFE (if slow) way is to charge gas (vapor) with the can upright. There is almost no way to slug a compressor with liquid by doing this.

Frankly, unless you have a little experience, have read the "book" and know how to use and interpret gauges and thermometers, you might just overcharge the system.

Under certain conditions, this can result in dangerous (for the compressor) high head pressures, liquid returning back to the compressor (more slugging) and a few other problems.

Don't feel bad, I used to maintain commercial and home refrigeration and AC/ heating, and I've found a few units operating dangerously overchaged, as well as undercharged --and it turned out there was no leak, either.

Undercharging is also not good, although usually you'll notice it as reduced performance. The bad for the compressor, is undercharging does not get ENOUGH cool refrigerant back to the compressor, and the valves and head can run too hot.
 
67Dart273 said:
Well both CAN be right--just depends on the situation and your experience.

The DANGER is that with the can upside down you are feeding in LIQUID, and piston pumps do NOT like liquid in the cylinders and valves. So if you feed in too much too fast you can "slug" the compressor. You might get to hear what a breaking rod sounds like.

The SAFE (if slow) way is to charge gas (vapor) with the can upright. There is almost no way to slug a compressor with liquid by doing this.

Frankly, unless you have a little experience, have read the "book" and know how to use and interpret gauges and thermometers, you might just overcharge the system.

Under certain conditions, this can result in dangerous (for the compressor) high head pressures, liquid returning back to the compressor (more slugging) and a few other problems.

Don't feel bad, I used to maintain commercial and home refrigeration and AC/ heating, and I've found a few units operating dangerously overchaged, as well as undercharged --and it turned out there was no leak, either.

Undercharging is also not good, although usually you'll notice it as reduced performance. The bad for the compressor, is undercharging does not get ENOUGH cool refrigerant back to the compressor, and the valves and head can run too hot.
Click to expand...

That makes sense for the R-12 in the old Cuda. Are the systems for R-134 the same, such as in My 94 Dodge Van? I've been putting in 2 cans per summer and it's been working for 10 years. (some day I should actually find and fix the slow leak).
 
Here's what the service manual shows for '72
 

Attachments

  • refrigerant.jpg
    18.8 KB · Views: 1,665
Only difference in R12, R134, or any other "Freon based" refrigerant is the operating pressures and temperatures.
 
I would evacuate the system, replace the receiver drier, check the V-2 compressor oil level then add your R-12. Don't patch it unless you don't like the A/C
 
Just use the sight glass on the top of the drier if you top it up. Add R-12 till no bubbles show then your full
 
Mr Hemi said:
Just use the sight glass on the top of the drier if you top it up. Add R-12 till no bubbles show then your full
Click to expand...

Actually, although this has been printed in many "tech" manuals, the sight glass is a VERY poor way of charging. This is because under certain conditions -- causing high head pressure -- charging to a "no bubbles" condition can result in a HORRID "overcharge."

Charge really should be weighed in or charge by superheat or subcooling or a combination of both

Vehicles are particularly difficult because of the problem of getting enough air through the condenser when testing.
 
it wont be easy to get the operation correct unless you evacuate the system first . Otherwise you wont know whats already in there . If theres air or anything other than refrigerant in there , itll always be compromised

ben
 
I work with this stuff.

You would be much better off with someone who can show you or do it for a price.

Other wise you seriously risk ruining some vintage/heritage equipment.
 
If you want the system to last a vacuum pump is mandatory. You shouldn't just ad freon to an empty system. Air is non condensable and contains water vapor. The extra volume of the air will mess with the pressures, and the water will turn to acid when mixed with r12. Don't forget to check the oil in the compressor. If it's even a little bit nasty change it with some mineral based A/C oil.
 
You must log in or register to reply here.
-

Back
Top