Last night I read the FSM, HAC specifically, looking for expected low and high pressure values. Or a pressure chart. I searched the pdf in case I missed anything too.

But I couldn't find anything. I found a few hints though.

I read that there's a sensor that will shutoff the compressor when pressure reaches 380 psi. And a valve on the compressor that will discharge refrigerant when pressure reaches 540 psi. From that I guess I can have the high pressure reach a maximum of 300 no problem. Right?

All official information available for this subject is that quantity of refrigerant that should be added (0.50 kgs ±0.25) nothing else.

Anyone remember the pressure values and outside temperate when their car was new? Maybe that's the last resort.

Even the quantity of refrigerant does not stay the same if anything else has changed. I NEVER use either weight or mass amounts when charging, simply hit the pressure numbers. Been doing my own a/c for 40+ years now.

I use the same running numbers as on any other vehicle out there, the gas does not know what car it is in. At around 95+ degrees I charge to around 25-50 max lowside (orifice or expansion valve will change that up a bit) and around 275-325 max highside, those pressures are locked to that high ambient air temp. Your 380# switch is an electrical shutoff and the other is a last resort one that bleeds refrigerant to the atmosphere.

You will NEVER find recommended values as they are locked into the ambient temps and change along with them. You look for temp/pressure charts elsewhere besides the car companies.

I found these charts online, I just assumed that every AC system was different and maybe every OEM had its own chart apparently not.

So, if I start charging until I reach the maximum limit per ambient temperature according to the chart. Then release a little of that refrigerant, is that good practice? Or maybe halfway between max and minimum expected pressures?

Why would you feel the need to release?, not mentioning that it's federally illegal.

The charts are for the GAS ONLY, they have nothing to do with who makes the system at all, it doesn't come into that. The gas does not care what system it is in, it is bound by physics to work as it does.

The OEM manuals if anything would vary the lowside numbers slightly based on the restricting method used there (orifice or expansion valve), the highside pretty much is to the gas characteristics and its' working and has nothing to do with design unless using something wonky like a variable output compressor.

You pressurize to the highside only, the low simply tells you how the system is restricting. The highside is what determines how long and how well the system works and why lowside only charging kits offered by the parts stores make such utter disasters. I used to sell them and saw plenty of grief there. They sell lowside only kits as a legal liability thing, you'd be amazed at how many stupid people have lost fingers and such due to incompetent use of the highside, you GOTTA think about it.

By releasing refrigerant I meant in case I reached a higher than wanted pressure.

(isn't the altima compressor a variable output compressor btw? I don't heat it engaging and disengaging like other cars).

I have one more question, since I'm stepping into new territory and experience with a 13 kg refrigerant tank. The tank has an open/close valve, how far should open that valve when charging? How long does charging usually take?

I ask that last after reading an article explaining why some people do liquid charging, it's faster. But the article didn't give any numbers so I don't know what to expect. I do know now to never liquid charge and tank should always be upright.

Open enough to see flow in your gauge setup. Be aware that the stupid little sealing collars inside every hand screw-together fitting you have there commonly grunge or wrinkle up to make for flow issues, if charging seems to be going nowhere suspect those plugging your port first.

You can liquid charge if the system is empty but you need some idea of what your static system pressure is (properly charged and running cold system that has been allowed to shutdown and rest, the pressure then equalizes across the whole system until powered back up and it becomes two separate halves again. I look at static as being around 90 psi on a 90 degree day, don't go all the way up to it but close, then bring the system up and running and then charge the rest of the way. If you turn tank upside down for a second you can see the pressure hits of solid liquid hitting the suction side, the lowside gauge will show big erratic needle jerks. Don't wanna do a lot of that at all. Not a race, better to just let the system eat refrigerant at the rate it wants to.

You are aware there are OEM service manuals on this site right? I'd download your needed one and look for more input in the a/c section of it.......................the manuals are worth their weight in gold quite literally.

Thanks for your help. I read HAC.pdf I just came here asking for things that weren't completely clear to me.

Anytime.............