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88 Cherokee a/c line thing

Very informative, I had not run across that yet. I may try it one day. What gauge pressures and outdoor temps did you use to charge/fill it?

Butt thermometer :rolleyes: ? LOL

I have one more upgrade job on my bucket list, may just try it. What oil did you use? The one PAG??? (IIRC) The one that works with remaining mineral oil so you do not need to do a pure/complete oil swap/flush?

Sorry, forgot to put that info in.
R12: mineral oil.
R134a: PAG oil.
R152a: POE (polyol ester) oil. It's allegedly compatible with remaining PAG and mineral oils but I don't believe it, several manufacturers disagree and say it is not compatible at all. Flush all lines and components clear of old oil before filling with new.

As for how to fill with the correct quantities of refrigerant - you have to do a molar equivalence. Take OEM refrigerant quantity, divide by molar mass of OEM refrigerant. Then multiply by molar mass of replacement refrigerant. Result is how much you should use. Seems to work fine for me so far - it's how I was taught, not 100% sure why it's the method to use. You can't really use system pressures IMO because once you have reached the vapor pressure of the refrigerant (somewhere around 80-90psi for R152a at 25C...) you're gonna have some liquid and there's no real way to tell how much. But, I'm no refrigeration expert and may be missing something.
 
R152a is flammable :(

What is your edu background?

I knew you were sharp, But most here would think Moles were animals LOL.

I use and H/L pressures and ambient temps, and vent temps from the evaporator to stop the fill process on mine..... Works fine for me.

Sorry, forgot to put that info in.
R12: mineral oil.
R134a: PAG oil.
R152a: POE (polyol ester) oil. It's allegedly compatible with remaining PAG and mineral oils but I don't believe it, several manufacturers disagree and say it is not compatible at all. Flush all lines and components clear of old oil before filling with new.

As for how to fill with the correct quantities of refrigerant - you have to do a molar equivalence. Take OEM refrigerant quantity, divide by molar mass of OEM refrigerant. Then multiply by molar mass of replacement refrigerant. Result is how much you should use. Seems to work fine for me so far - it's how I was taught, not 100% sure why it's the method to use. You can't really use system pressures IMO because once you have reached the vapor pressure of the refrigerant (somewhere around 80-90psi for R152a at 25C...) you're gonna have some liquid and there's no real way to tell how much. But, I'm no refrigeration expert and may be missing something.
 
i ended up vacuuming down the system again i may have been over charged. based on some write ups i have found the ~36oz of r12 should convert to 24oz of 152a. yesterday in ~90 degrees out and i had ~15psi low and ~170psi high. vent temps went down to 38 degrees where the cutout switch is set at.

I never changed the oil out on this system but changed the dryer when i changed the condenser. i do plan on changing the entire system out and when i do im going to get all new parts from a stock R134 system. but until then it seems to be doing good. ran all last summer on it and there was no gunk or yuckums in the hoses. i do get some frost formation around the muffler in the suction hose but i verified it is not clogged with anything.
 
R152a is flammable :(

What is your edu background?

I knew you were sharp, But most here would think Moles were animals LOL.

I use and H/L pressures and ambient temps, and vent temps from the evaporator to stop the fill process on mine..... Works fine for me.

I'm an EE... I took 4 or 5 college chemistry classes over the years but wouldn't consider myself more than a reasonably well trained amateur.
 
I'm an EE... I took 4 or 5 college chemistry classes over the years but wouldn't consider myself more than a reasonably well trained amateur.

We seem to have some folks here and there with impressive EDUs, like yours, other than just hard knocks mechanics, Nice. Mine is Env/Bio-Chemical Engineering, 2 US DOE R&D grants to my own company (Me). Back when I was younger and still full of P&V LOL. Getting too old now, and too many health issues to keep up that pace now, but my Son just got his BS-Physics and eyeing a Masters in Computer science areas...He moved up from a Ford last year to a Jeep Liberty. Eyeing some Wranglers...

It's a real shame that the masses are not more chemistry literate. I love to send them to the dangers of DHMO web site LOL.
 
I'm an AE. Five years of my USAF time I spent on strategic missile programs so I was actually a rocket scientist for a while.

Still didn't help changing out the rear main seal in my '88. :(
 
LMAO_Emoji_-_Watermark.jpg


I'm an AE. Five years of my USAF time I spent on strategic missile programs so I was actually a rocket scientist for a while.

Still didn't help changing out the rear main seal in my '88. :(

I worked for an Aeronautics Engineer, guy with pump patents in my early 20s, learned a lot in 2 years there.
 
We seem to have some folks here and there with impressive EDUs, like yours, other than just hard knocks mechanics, Nice. Mine is Env/Bio-Chemical Engineering, 2 US DOE R&D grants to my own company (Me). Back when I was younger and still full of P&V LOL. Getting too old now, and too many health issues to keep up that pace now, but my Son just got his BS-Physics and eyeing a Masters in Computer science areas...He moved up from a Ford last year to a Jeep Liberty. Eyeing some Wranglers...

It's a real shame that the masses are not more chemistry literate. I love to send them to the dangers of DHMO web site LOL.

Impressive? LOL, everyone has a bachelors like me now.

This forum taught me the hard knocks mechanic part. I didn't even know what a dana 30 was, or what a pinion seal was, or why my differential was leaking when I joined here, but now I have owned a half dozen of the damn things.

My personal favorite is warning them about 1-oxamethane, or refrigerant R718, or oxidane :roflmao:
 
LOL, I hear the R178 is one of the best coolants/refrigerants there is, but is highly dangerous and can cause severe third degree burns way too easy! Not to mention the planet is severely contaminated with it and its a major cause of global warming?
 
R718 does have a GWP but I think R744 might be higher. :looney:
 
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