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How much refridgerant, how to tell?

73Wagoneer on Tue January 06, 2009 7:58 PM User is offline

Just wondering for the DYI , recharging A/C systems, with the basics tools, air pump for vacuum and guages, lets say you want to add 22oz of 134, the cans come in 12 oz cans, so what is the best way to make sure you have the right amount? do you go on the pressures? or maybe just vents temps? or combination of both

Thanks Robert

Edited: Tue January 06, 2009 at 7:58 PM by 73Wagoneer

Dougflas on Tue January 06, 2009 8:11 PM User is offline

You mentioned that your system requires 22 oz. The cans are 12 oz ea. By the time you purge your hoses and take into account the amount of refrigerant your hoses hold, you can be safe to put the two cans into the system. If you weigh the charge into the system, make sure you relieve the pressure of the hoses on the scale.

A system that uses a TXV is not that critical as the purpose of a drier is also to store extra refrigerant so that when the TXV opens, it has a full stream of liquid.

A system that has a fixed orfice system can be charged by measuring the temp of the input and output of the evap. When they are real close to the same temp, add another oz or two. I've done this for years and it works well.

If I have a system that is giving trouble, I'll pull the charge and weigh in an exact amount. This will eliminate the charge as a source of the problem.

73Wagoneer on Tue January 06, 2009 8:27 PM User is offline

Ok thanks for the info, lets say I wanted to do the wiegh method, where could I get the proper scale? I did not see any on the Arizona Mobile site

How to measure the temp of the input and ouput of the evap, is it just as simple as feeling the difference in temp of the lines with your hand?

Edited: Tue January 06, 2009 at 8:29 PM by 73Wagoneer

TRB on Tue January 06, 2009 8:53 PM User is offlineView users profile

Mastercool Accucharge

Now any good digital scale will work for weighting the difference in a can of refrigerant. The Mastercool has some nice features if you are working with more than one vehicle.


When considering your next auto A/C purchase, please consider the site that supports you:

Edited: Tue January 06, 2009 at 8:53 PM by TRB

Chick on Tue January 06, 2009 11:08 PM User is offlineView users profile

You cannot beat that mastercool scale, I wouldn't charge a car without it.. Think about one in your future if you plan on fixing other cars, and the price here is beyond reasonable.., buy a 30 pound tank, you'll save a lot of money that way.. But for the car mentioned, go with adding the two cans in, or as much of it as you can get in..As stated, you'll lose some switching over the cans.. Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

mk378 on Wed January 07, 2009 10:21 AM User is offline

The Mastercool scale will work for cans too. It resolves to 1/2 ounce. But once you have a scale, forget cans and buy a 30 pound cylinder like Chick said. It's a lot more precise, there's no loss in changing cans over, and much less expensive too. Also when using cans, it is hard to store a half-full can for next time because the can tappers tend to leak.

Dougflas on Wed January 07, 2009 6:24 PM User is offline

To answer your question if you can put your hands on the input and output, no you can't.. Either use a clamp on probe or an infared type. Mind you, a IR has an error due to the reflectiveness on the alum. tubing. As long as both tubes are the same "shinniness" you can use the IR. You are just looking for the same temp.

73Wagoneer on Wed January 07, 2009 8:45 PM User is offline

alright thanks everyone for all the advice, maybe with my tax refund, i can get a scale and a 30 pound tank, I do recharge a few of the neighbors vehicles, so I can see where it would be worth the mulah and less hasle changing cans out.

I do have an IR temp gun, or maybe I can use the turkey thermomerty from the kitchen LOL

Thanks everyone


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