AC Refrigerant Question

[RonRock]

I have read that having the exact charge is especially important with R134a systems. I am charging with the 12 oz cans. I have weighed a full and an empty to come up with a weight to expect from each can. But there is always some loss when changing cans, clearing lines and etc.

So I have an old charging cylinder from the days of R12. I think it has graduations for R12 and R22, maybe others been a while since I looked at it.

Can I use it to measure R134a? Will the scale be correct? I figure I'd flush it with some 134 first, then use it as I used too.


As an aside bit of info. I am charging my daughters Jeep 05 Grand Cherokee. I can't get the system to work as expected. My High side goes high and the Low side stays lower than I think it should.

 

[goingtoarizona]

If you assume 12oz per can you'll be close enough. For best results evacuate the system for 60 minutes before charging. Pressure should be around 35 low, 170 high.

 

[jimindm]

It is true that the exact amount will work the best for the most part.

While R12 would work pretty good if close. Close being a half pound or so. R-134 is a lot less forgivable. It needs to be close, by say ounces.

I charged many before I got a machine. IMO you are over thinking it. a 12oz can is 3/4 of a pound.

I think the specs are somewhat loose enough that a little loss while changing a can or what is left in the charging lines, is somewhat figured in. While the spec is a spec,
you just have to kind of get to figure out your charging system and what it contains for freon.

If you are that concerned, maybe take it somewhere and have it charged.

 

[wrench409]

If tbere is residual oil in the R12 machine, and there always is, I would flush it before using it on R 134 charging.

 

[Schurkey]

I am charging my daughters Jeep 05 Grand Cherokee. I can't get the system to work as expected. My High side goes high and the Low side stays lower than I think it should.

High side high, low side low...I'd be looking for excessive restriction at the expansion valve/tube. A screen-full of debris would be my first guess.

You'd also have poor cooling, because you aren't getting enough refrigerant into the evaporator.

 

[Super Mech]

How high is the high side and how low is the low side? What is the outside air temp? Is the radiator fan coming on when the a/c is on? Need more specifics.

 

[RonRock]

High side high, low side low...I'd be looking for excessive restriction at the expansion valve/tube. A screen-full of debris would be my first guess.

You'd also have poor cooling, because you aren't getting enough refrigerant into the evaporator.

I think you are on to something there. I was going to ask about that, but I don't know enough about this system to know if it has an expansion valve or tube. Sounds like a little more study is in order on this particular system.

I appreciate the help.

 

[RonRock]

If tbere is residual oil in the R12 machine, and there always is, I would flush it before using it on R 134 charging.

It is not a "machine" it is what used to be called (at least by myself and the guys I worked with) a charging cylinder. Basically a cylinder with graduations that had scales for different refrigerant amounts based on ambient temps. Old school tech. But it would never have any oil in it just refrigerants.

How high is the high side and how low is the low side? What is the outside air temp? Is the radiator fan coming on when the a/c is on? Need more specifics.

I knew I should have added these important facts. Thanks for asking. The fan comes on. Ambient was 80* F. Gauge pressures were 180/22 at idle. If I throttled it up the high side would go up until the high side switch cut it out. And the low side would drop well bellow the freezing temp.

 

[LS6 Tommy]

I'm pretty sure that system has an orofice tube. My guess is a restriction, too.

Tommy