rowjelio
Member
Gonna fille my AC system up, what's normal low side AC and high side pressure at idle? Thanks! It's 2.5 pounds right ? The shop manuals are confusing about this stuff hah thanks!
What's good AC pressure on low side at idle?
- Thread starter rowjelio
- Start date
Justin Plant
Well-Known Member
Low side should read the temp in the vents or damn close.
Pressures seen on the gauges WILL vary by ambient temperatures and engine speed, PLUS the temp of the air crossing the condenser. Which is why, at least in TX, almost everybody that tried to check charge levels in the summer time had a 36" fan mounter on the wall to blow air to the condenser (with the hood up), when seeking to check "poor cooling" of a factory a/c system, to better simulate "driving down the road" in the service area's stall. As the a/c blower motor was running on its highest speed.
This variability is probably why you did not find the specs you were looking for. Although there might be some pressure ranges of "full charge".
MIGHT be a good idea to look at the sight glass on the receiver/drier to determine if more gas is needed! Even with a 45*F vent temp, there can be some random bubbles pass the glass as the system is modulating itself. A system that is low will have many more bubbles, even "foam"-like and more constant bubbles.
What refrigerant gas?
CBODY67
This variability is probably why you did not find the specs you were looking for. Although there might be some pressure ranges of "full charge".
MIGHT be a good idea to look at the sight glass on the receiver/drier to determine if more gas is needed! Even with a 45*F vent temp, there can be some random bubbles pass the glass as the system is modulating itself. A system that is low will have many more bubbles, even "foam"-like and more constant bubbles.
What refrigerant gas?
CBODY67
volksworld
Well-Known Member
R12 or 134 ?
Till theres no bubbles in the site glass, and NO more.
Is your system EMPTY?? Because the weigh in is meaningless to you otherwise, and i would think 2.5# is not enough for a big Chrysler otherwise, unless maybe its been converted or is non stock setup.
Is your system EMPTY?? Because the weigh in is meaningless to you otherwise, and i would think 2.5# is not enough for a big Chrysler otherwise, unless maybe its been converted or is non stock setup.
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In general, the Chrysler RV-2 compressor systems took 3#-3.25#, or possibly 3.5# for the single, front-only systems. The wagons with dual a/c would be higher, probably closer to 4# or so.
The total capacity might be in the Factory Serv Manual, BUT was always on a silk screened metal tag on the top of the compressor, from the factory. Using R-12 gas. R-134a can be abt 90% of that amojnt.
CBODY67
rowjelio
Member
don't kill me, i'm gonna try R152A , AKA, air in a can
R12 Molecular Weight: 120
R152a Molecular Weight: 68
R12 original charge: 2.5 pounds
You'd need approximately 1.42 lbs of R152a to replace 2.5 lbs of R12 based purely on molecular weight.
You'd need approximately 1.7 lbs of R152a to replace 3 pounds of R12, based on their molecular weight ratio.
R152a is apparently a drop-in substitute for R134a, and if you were to use R152a in an originally R12 system it's the same prep work involved in going R12 > R134a.
But I'm going to shill for Duracool/HC12a again - if you can get your hands on the stuff get it, it's great.
But I'm going to shill for Duracool/HC12a again - if you can get your hands on the stuff get it, it's great.
rowjelio
Member
R152a is air in a can and it's about $7 a bottle of 10 oz. There are numerous people online who say they just threw r152 and their R12 system and it works great. So I'm going to try it
rowjelio
Member
I'm seeing mixed things online about r12 mineral oil and r152. On paper they aren't compatible, Various people online say it's fine and works great. I talked to an old timer AC guy , he says these old compressors don't really care about what oil is in it, they aren't as sensitive as newer things. So I'm gonna take a chance and just fill it with 152 and see what happens. What's the worse case scenario here, I pop a line ? The compressor dies ? Good then I'll replace it wth a Sanden compressor
R134a oil isn't compatible with the mineral oil that R12 needs. If the system was already emptied and filled with R134a after, the R134a oil will work with R152a refrigerant. If it still had R12 in it then it's very likely you'll need to remove all the mineral oil in it.
Worst case is that you might gum up the system and end up replacing parts that are a pain in the *** to replace, like the evaporator core, or the expansion valve etc.
That being said, some people have also gotten away with just removing some - not all - of the mineral oil, replacing that with ester oil, then regassing with R152a.
Worst case is that you might gum up the system and end up replacing parts that are a pain in the *** to replace, like the evaporator core, or the expansion valve etc.
That being said, some people have also gotten away with just removing some - not all - of the mineral oil, replacing that with ester oil, then regassing with R152a.
rowjelio
Member
You know what, ester oil is compatible with mineral oil, and esther oil is compatible with r152a, so how about I vaccum pump it out, and then since I will be putting less refrigerant than r12, I throw some ester oil in there too
Carmine
Old Man with a Hat
I was just going to do a "report" on this, but wasn't done with trying it out yet. I had a system which hasn't been run for at least a decade, but still had enough pressure to engage the compressor. However it didn't cool. Figuring much the same thing you did, nothing to lose.. I tossed in one can of Air Duster which took my high-idle low side head pressure from about 30 PSI to 50 PSI on a humid 90+ degrees day.
That did not get rid of the bubbles in the system but it did start giving decent cooling so I ended the experiment at one can. I do have read the contradictory information regarding compatibility with mineral oil. The best I can see is that you should run Esther oil, but not the PAG oil.. I figured that since the system was operating with whatever was left inside by the previous owner a decade ago, it wouldn't do much harm to add one can of Air Duster. So far I have driven the car about 40 miles at highway speeds with the AC operating. So far so good.
That did not get rid of the bubbles in the system but it did start giving decent cooling so I ended the experiment at one can. I do have read the contradictory information regarding compatibility with mineral oil. The best I can see is that you should run Esther oil, but not the PAG oil.. I figured that since the system was operating with whatever was left inside by the previous owner a decade ago, it wouldn't do much harm to add one can of Air Duster. So far I have driven the car about 40 miles at highway speeds with the AC operating. So far so good.
rowjelio
Member
So what got me into 152, was that the system has a leak, but I needed to put DYE in it and run the system..but I wasn't going to buy r12 for the sole purpose of it leaking out. So I saw YouTube videos of people filling their r12 systems with propane cans from the camping section, or air in a can. Air in a can seems to be a mix of propane and butane, whereas propane is just raw propane. So I did like you and filled it. It worked well, cooled the air. I also only did a can and a half. I saw no adverse effects on the system. If I had a third can I would have put it in! I was impressed to be honest! However since I never vacuumed out the system before filling, it was a mix of both ambient air and the 152, which made the high pressure line run hotter than normal (I assume you did the same, and if you touch your high pressure tube it should be hotter than normal). So when I fill again, I'm gonna vacuum out all the air, and just do straight 152.
Once I replace this kaka Schrader valve that collapsed inside the tube, I'm gonna put a little ester oil, and try the air in a can again!
Oh and the cheapest I can find is 10oz for 6.99 at harbor freight, but you MUST make sure it says it contains "1,1-Difluoroethane 75-37-6" most air in a cans say this, or a variant of this wording, but a couple brands do not. Which means they are something else.
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"Vacuuming" the gas will not remove the oil with it. I presume that the old comments about "too much oil hurts cooling" still apply?
I had a Mopar parts friend who ended up working for Four Seasons when they were doing the initial research on R134a gas and its performance in R12 systems. Back then, the oils were not compatible, with the mineral oil congealing in the low spots of the system (condenser, for example).
He said the only way to get the old oil out was to put the R12 recycling machine on "liquid" and sweep the system with R12 to get the old oil out (as the machine would then clean the gas of the oil so the gas could be returned, adding to complete the full charge, and then add oil back into the system at that time.
Of course, changing to R134a would mean that after the R12 and oil were cleaned from the system, then a R134a recycling machine would need to be connected to the system to add the new gas and R134a oil into the system as needed. Those were his comments back in the 1990s.
I was monitoring the a/c forums back then. Many posters claimed they used butane and such to add to or replace R12 with with good results. Yet it all seemed a bit sketchy to me, especially if a crash resulted in a broken a/c line and then things kaboomed when heat/spark was added. FWIW.
Whatever works,
CBODY67
I had a Mopar parts friend who ended up working for Four Seasons when they were doing the initial research on R134a gas and its performance in R12 systems. Back then, the oils were not compatible, with the mineral oil congealing in the low spots of the system (condenser, for example).
He said the only way to get the old oil out was to put the R12 recycling machine on "liquid" and sweep the system with R12 to get the old oil out (as the machine would then clean the gas of the oil so the gas could be returned, adding to complete the full charge, and then add oil back into the system at that time.
Of course, changing to R134a would mean that after the R12 and oil were cleaned from the system, then a R134a recycling machine would need to be connected to the system to add the new gas and R134a oil into the system as needed. Those were his comments back in the 1990s.
I was monitoring the a/c forums back then. Many posters claimed they used butane and such to add to or replace R12 with with good results. Yet it all seemed a bit sketchy to me, especially if a crash resulted in a broken a/c line and then things kaboomed when heat/spark was added. FWIW.
Whatever works,
CBODY67
Carmine
Old Man with a Hat
I purchased six cans of Office Depot air duster for $35 from Amazon. It does contain diflorothane (95.5%) (R152) and some kind of bittering agent so morons don't huff it.
One good way to find out if something contains the ingredient you're looking for is to look up the MDS ( material data safety ) sheet. Just keywords on Google, something like "Office Depot + MDS"
Somewhere I did read that r152 was and approved R12 substitute by the EPA because it disappears in the atmosphere within hours. It is pretty much the propellant that has been used in aerosols since the 70s. Supposedly GM was considering this rather than R134a when the big switch occurred in the 90s.
One good way to find out if something contains the ingredient you're looking for is to look up the MDS ( material data safety ) sheet. Just keywords on Google, something like "Office Depot + MDS"
Somewhere I did read that r152 was and approved R12 substitute by the EPA because it disappears in the atmosphere within hours. It is pretty much the propellant that has been used in aerosols since the 70s. Supposedly GM was considering this rather than R134a when the big switch occurred in the 90s.
68yourker
New Member
When the system is discharged too quickly, some oil will come out. The oil tends to get trapped in the condenser, evaporator and the receiver dryer. All of those locations, will be less than what is in the compressor. The correct oil for the refrigerant used is needed to protect the compressor (only part in the system that requires lube). If too much oil is added, it can cause the high side pressure to sky rocket and performance will be poor (oil doesn't transfer heat as well as the refrigerant can). Some of the systems that used the RV2 compressor had a valve in the inlet port of the compressor(EPR-evap pressure regulator or ETR-evap temp regulator), and it's job was to keep the evaporator at 30 psi (test gauge pressures were never at idle but around 1,500 RPM with good airflow across the condenser). These systems also had 3 test ports-one in the low hose, one in the high hose, and one in the compressor head (gauge on the head could be between a vacuum to the same as low side pressure). If there isn't enough air going across the condenser, the high side will climb, and there will be bubbles in the sight glass, even on a fully charged system. Back in the day when I worked as an auto tech, I did a number of conversions to 134A, and they worked good so long as you use 80% of what was used as R12, and provided good flow across the condenser. After the EPR-ETR valves were removed, there was a sensor bulb that measures the evaporator temp, and when it got close to freezing up, would kill the power to the clutch, until the temp climbed above the freezing point. This type of system, the low side gauge readings would need to be observed when the clutch is engaged (pressure gauge could be between 5 PSI to 50 PSI). Lots of variables.
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