Hi GeorgeLG. I thank you for your excellent and highly informative posts. I like when people give me a lot to read with all the information so that I can look at it and then look at it again and put some things together your posts are really great.

As to the Green oil maybe Green Slime. You are correct that I don't really know which one it is although I'm trying to look at how bright it is and the consistency of it... it looks more like oil in slime to me because it's very new and doesn't appear to be dirty in any way. And it took some doing but I think I got the Schrader valve to close I put my ear by to the thing and if I hear no hiss then I consider it close if I'm here even if the faintest hiss I keep playing with it until I don't hear it anymore.

The compressor has absolutely gotten quieter since this whole Adventure in getting it to run right has begun.

it seems to be cooling gradually better just about every time I run it so if I am in fact purging air ? then it seems to be doing something.

And like I thank you also still giving me the information and not just telling me to go and buy things or just take it somewhere I'm doing the best I can with just the low side port so I thank you very very much

 

If you are releasing a gas into the atmosphere you have no way of separating any air that might be in the system from refrigerant in the vapor state so you are most likely intentionally venting refrigeration into the atmosphere. See my prior comment about that. The entire purpose of the accumulator that the low side schrader is attached to is to keep the low side in the gas state even if the system is overcharged or in a very light load situation. If not for the accumulator, such a system would pass liquid refrigerant to the compressor and "slug" it which is to kill it. The compressor acts on a gas not a liquid. That port will always release a vapor unless something is terribly wrong. It will not release air unless something is wrong. If the system is running better as you are venting refrigerant into the atmosphere it is because the system was overcharged to begin with. This cycle of overcharging and venting will be adding more oil and stop leak into the system, stressing the compressor, and polluting the environment. Again, most systems are overcharged not undercharged.

George

 

Yes, I get what you're saying that I shouldn't be doing it the way i am. Okay I get that. But. I can tell you.. that. Yes "static pressure" i put the gauge on without the dashboard switch for AC or compressor engaged. My static pressure is anywhere between 60 and 150psi; probably about 90. Then I turn it on and i see like 49/50lbs.. less than it was. So. When i squeeze that lever. Only a little looks like AIR (no "particles " in it) came out.. when clearly refrigerant sprayed out, I stopped.

The result was that.. in about 30 seconds, i had cool air in the cabin. About 5 minutes later it got colder.

I do not know if I'm overcoming a blockage or if I still have too much oil or if I'm doing a good thing by purging are on the system or if it was just drastically over. Or if I'm helping the refrigerant move around and circulate as it should for my compressor is just tired but I mean again to compressor is a lot quieter the engine seems to have a lot of struggle when I disengage the compressor not engage it but I'm not adding refrigerant because I think there may have been way too much in there and I also am compensating for when I didn't know the compressor was even plugged in because it used to not come on at all due to electrical.

Oh and when I saw the spray of refrigerant. The gauge was at about 40/42. Previously.. it would be more around 45. This is another reason I feel it is "getting where It is supposed to be" ? Obviously I am a backyard guy. Still learning technique and info.

Also. Nice puddle of water too after 10 minutes. 75 degrees outside temperature. 81% humidity. Yeah, could put windows down, but I know something is doing something because I can feel cool dry air. Maybe I should buy a vent temp thermometer?

^ I notice smoother disengagement of the compressor/compressor clutch as well after doing that a 2nd time. Most came out instantly too.

 

At rest, system off, your system pressure on a 76F day should be 79psi (see chart), identical at either the low or high side test/gauge port. Note that automotive 134a ports are usually but not always different than HVAC and refrigeration ports. They are usually quick connect with ball check valves. The gauge connectors have a dial to turn down after the line is snapped on to the fitting to depress the ball. Std refrigeration at this system size are usually 1/4" flare with schrader core valves. The valve is depressed as you thread on the fitting. This is whats on the accumulator. This accumulator port is often used for the low side switch and not for measurement.

When the system turns on the low side drops and the high side increases as the compressor compresses the low side vapor into a hot high pressure vapor. Then the high pressure vapor passes through the condenser to cool the hot compressed gas at which point it undergoes a phase change into a liquid. That phase change releases heat which is removed by the condenser. That high pressure liquid 134a is presented to the orifice tube which "meters" the passing of the refrigerant to the other side and causes a pressure drop. That pressure drop causes the refrigerant to undergo another phase change to a cool gas which is passed over the evaporator coils in the cabin to cool.. That "spent" vapor heads back to the compressor to rinse and repeat. All of this pressure/temp/volume/phase change behavior is described by the ideal gas law which shows how those 3 variables are related. Change one side and the other side changes (with constants left out) > PV=T. A rule of thumb for a generic system at 75F would be pressures of 35-45psi low side and 150-170psi high side (see chart). That's just a guide, the way to an optimum system is to weigh the charge in per the nameplate. If your going to keep working on this system then you need an inexpensive vent temp gauge (see pic).. Too much gas equals reduced cooling. Too little gas equals reduced cooling. If you really want to do AC right then you need evacuation machines/bottles, vacuum pumps/manifolds/hoses, digital micron vacuum gauge, a good manifold set, a 30 lb bottle of 134a pure gas and an EPA cert card (609 for auto, 608 for residential).

I am going to assume that you are releasing refrigerant from the accumulator schrader which is on the low side and is at the top of the accumulator where the refrigerant should be a gas. If liquid is being released then the system may be overcharged unless you mean a foamy sputtering liquid is being released. that may be refrigerant boiling into a frothy gas mixed with oil due to the pressure drop (lower the pressure enough and a liquid boils at room temp). That's why water boils at a lower temp on a stove in the mountains. It can also be just oil because the accumulator design brings oil up from the bottom of the accumulator to mix with the gas. Either way, it should not be liquid refrigerant which by the way can be hot enough to burn you (high side) and cold enough to give you frostbite (low side)

What are the high side and low side pressure when the compressor is running? What is the center vent temp on high blower fan when the cabin is cool? Does your system have a site glass? That's the s**t for winging a top off charge.

I don't know if your overcharged or not.

George

 

Hi George. You are awesome. Slow night at work tonight so.. let me answer as much as I can in the time of this break I have.

OKkay. The last time I released the stuff from, yes, the low side port on the top of the accumulator that sits off at an angle that my gauge that says AC Pro - but that tall can is sitting in my garage and i just put in regular cheapy $5 Walmart "R134A Tetrafluoroethane 1,1,1,2" cans............ with it... with that gauge.. it was a smooth, nice, spray, almost like fuel from a perfect fuel injector
or the "mist" from a shower head
Knowing it could be cold, I always aim it away.
and
in the split second it took to see that it was no longer "JUST AIR" (there were times where NOTHING came out.. just air. That has stopped as of today) - I stopped immediately
because
I did learn that "if you see refrigerant, stop."

That, I did with the system off.

Now. In times previous. Yeah, I saw the foamy, looked like oil or little beads of stuff almost like Nickelodeon Gak. That has stopped coming up/out. It used to produce that when I did the same procedure on a RUNNING system.

The cool air seems to be getting cooler. I agree I need the vent temp thermometer again.

I *think* I am at about 40-42psi low side with it running now. Probably 40 since I let out a small amount.

I am unsure how much oil is in there.
I have pressed the high side port as well and it too mists out like the water fountains at the end of Ocean's Eleven (the only good one of those films.)

I hope I am on the right track here.

The compressor sure is more quiet, and again, i don't feel the entire RPMs of the truck bog/cut out like it was doing when I turned it off. Like the truck wanted to stall, ... so. I'm thinking "less resistance." I will verify after a long drive but I've done so at least twice now and it seems to be shutting off smoothly.

I am thinking I was way overfull, mix of frothing oil and air, making compressor strain.. and now it is probably close to, but not perfectly in, a good range.

And i have never put my gauge on the high side. It cant handle it.

?

 

I’m not clear on why you keep releasing refrigerant from the system. It sounds like you read something that suggests that you do this. What is the goal? You keep saying air so do you believe that you have non-condensables like air or moisture in the system that need to be purged? If so, why do you think that those things are in your system? Are you doing this with the system at rest or with the compressor running?

George


George

 

These are excellent questions. Let me try to answer them.

1. I believe I AM OVERCHARGED.
I will share a story about why I think what I am doing is helping.
My Mom has a Chevy Cruze. Her AC was "marginal" to barely/not working.
One day, after reading about what Overcharging a system can do. (Gets cool, then hot. Doesn't cool. Doesn't cool well. Gets cold two minutes then hot 5 or something like that.) Her fan, an electric one, was SCREAMING as in, running on the highest setting.
While releasing stuff in the manner I describe now and on the Blazer, i heard the fan go from high, to medium, then to low, just before it misted out refrigerant.
I do not know if it works perfectly, but her High Side port is untouched and her air conditioning works "pretty well" now. Especially for a Cruze. Which is actually a cool little car. Just tiny.

2. The goal is to a. Get air out of the system b. Get the system to COOL BETTER with the tools I have.

About the atmosphere thing. Everyone that uses canned air to clean a computer is guilty of the same.. saying that, then moving on. I have Air conditioning I need to get right, kind of brings us to where we are.

3. Yes, I DO believe there is moisture/something in the system. By releasing air, I do actually hope to "boil" some of that out. I do not fully understand how vacuum boils things but, I did hear the cracking/sizzling when Schrader valve was partly open and I didnt know how to close it.

When that happened (Schrader valve open partly,) some but not all refrigerant came out. Trail of green stuff as well as bubbling at valve. Moisture may have got in then too. I also know "There is not supposed to be any."

I also THOUGHT I had a leak. It may have been the valve.. which I poke with a screwdriver.

I just may make video of this in the morning. after I wake up.

So, now I get to add in this mix and learn.

And I feel the air getting colder. It could be STRONGER, sure, but that first steamy hot day. I think I am increasing the coolant capacity.

Have I done an OK job of shedding some light?

^ "Am I doing this with the system at rest or running?" - I seem to have better results doing this with the car running, AC system OFF.
So.. At rest.
I have done it with it running but I'm seeing signs i am close to getting it... and it seems to be better result with it at rest before I start up the AC system by turning it on at the dash. Engine running...
I've never checked it engine off system off..

 

The temperature outside, going home, will be:
71 degrees
89% humidity.
I do not know, nor understand, the Dew Point
and 100% humidity is "supposed to be raining."
Might even be driving through fog again. 3rd night in a row. GSP. Construction.. everywhere.

Traveling between 65 to 75MPH the whole way. I move the AC from MAX AC (?) to AC to TWO ARROWS (?) and it seems to get the coldest on TWO ARROWS.

Whatever is in there gets really circulated...

 

Ive given you a good background in how your system functions and some suggestions for how to do this correctly so I think I’ve gone as far as I can.

I am unaware of any HVAC procedure that involves constantly removing refrigerant until liquid comes out. Your system is either charged correctly or it’s not and venting until you see liquid does not tell you anything about your state of charge. All normal systems have both liquid and vapor refrigerant in them. The gas that you are discharging is not air, it’s refrigerant in the vapor state. I wish that you would stop venting refrigerant into the atmosphere, it harms the environment and it’s illegal. In addition, you can hurt yourself.

The only way to asses the state of your system is with a vent thermometer and a set of proper gauges for 134a and with automotive quick connect fittings, if that’s what you have. I will reiterate one last time that the proper procedure is evacuation into a reclaim cylinder such that only deminimus qty or refrigerant are released followed by nitrogen pressure testing and leak detection followed by a proper vacuum followed by a weighed charge. Absent that, a proper set of gauges, a vent thermometer and some experience can get you running but not optimally. This also helps you to determine if you have actual air in the system. Continuing to add 134a because a system is not cooling can work but often results in an overcharged system. That’s what the gauge set and thermometer are for. There are other procedures like measuring line temps etc but I won’t go there.

a vacuum removes moisture because when you lower the pressure it allows the water to boil at room temp and the water goes into the vapor state where it is removed by the vacuum pump. Without this process, water stays in the liquid state trapped in places around the system reacting with the oil and forming corrosive acids. This kills the compressor and can cause sludge and a blockage. The desiccant in the accumulator helps to a point with trapping moisture but it’s a safety net not a strategy.

My work is done here. Good luck with your project.

George

 

I do see the concept of removing air from large commercial systems with purge valves back in the olden days but I have never seen that in small systems. In todays world your allowed to reclaim refrigerant and let air out of the top of the reclaim cylinder if its found. That's more precise and easy to control, and you can verify with pressures, flame tests, etc. The layperrson will not know the difference between air and refrigerant in the vapor state. Again in an automotive system with such small amounts of gas, its a breeze to do the proper proceedure with the right equipment and you get a better job.

Good luck,

George