Well let me shed some light on it.
Usually this happens because we've a habit of going to any ac shop and getting the refrigerant purged in the system, or excessive oil addition in the system or drier is not replaced and it has sludgy oil present in the drier or condenser. Once it swings around completing its cycle every part face's blockage because that sludge becomes frozen when refrigerant is passing by and it blocks the ac refrigerant flow resulting In poor ac performance. If the system has started to get bad. Just buy Ctc aka carbon tetra chloride, it cleans up the ac system and gets dried up. Then replacing the drier or any part that has excess of that sludge trapped in. Usually evaporator condenser or drier traps that sludge.
So this kind of system shows high head pressure
One more note whenever ac people don't measure how much refrigerant a car requires, or the compressor oil they screw the system by by excess addition. You can search over the Internet or the hood or front bulk Head has a tag of refrigerant capacity on it.
The real issue arises by Toyota 2009+ compressors, solenoid switch one. The complain usually is the ac shuts down in between and then turns on after some time.
This type of problem usually happens because of bad solenoid switch. If you get new switch and the switch is carefully pulled out with some tool the compressor can be saved. But finding new solenoid is a hassle here.
So most ac shops add clutch compressor that comes in 2006 Toyota nz engines that works greatly for 5-8years and you can get the magnetic coil or clutch easily available if it gets bad. And condenser changing + Txv changing and compressor replacement is the only solution to get your system going.
I'm telling u this about Toyota nz or vitz solenoid switch.
Normally other manufacturers don't require compressor swap that easily unless having some malfunction.
Nowadays refrigerant has gone to the sky rocketing prices of 65k USA and other Chinese refrigerant for 34-35k so no one would try to discover things on saving anyone's system or there pocket, everyone will play safe.
Because end users run in with complains if they change kabli compressors and they do same behaviour so no ac technician would be that rich to bear the refrigerant or compressor loss. So in the end enduser wants cool air not someone who experiments on the old clogged condensers or evaporators or compressors.
This is a very important piece of information I'm giving everyone before the start of this season 
however I don't like Chinese refrigerant so I've kept USA honeywell. No matter how expensive it is. Obviously I'm going to charge accordingly considering the quality I'm offering.
