An ounce or two of refrigerant should give you plenty of pressure for a leak test. No need to fully charge the system.

Manifold valve leaks and service hose / connection leaks happen occasionally. More common on rental / loaner units...

You can place the LPCO in series with the HPCO when installed in the High side of the loop.

This will inhibit compressor operation below about 25f ambient, and when the system is completely empty - static pressure below 30 psi.

A little protection from the worst events.

Side can tap is the only way to go. Always works, any size can.

Year / Make / Model of your car would help us with a diagnosis.

Low side service connector not depressing the Schrader valve. You have charged the service hose.

Try depressing the coupler a little bit to see if your low side gauge drops.

A blockage at the TXV would result in a reduced low side pressure as the refrigerant stacked up in the receiver dryer. If the TXV was restricted you should see calm liquid in the sight glass. The receiver is designed to deliver liquid to the TXV. If the flow is reversed it does a lousy job of that. ...

Receiver / Dryer installed with flow in the right direction?

Well, we didn't have a Cadenza here in the US, but the 2011 Sorrento has the 3.5L V6. The 3.5 has a direct drive compressor, with an electronic control valve. It runs 100% of the time. So your issue could be an undercharged system, a bad control valve, a wiring issue or a worn out compressor. Start ...

Bummer. There are a bunch of relays someplace in that truck. I wish Mopar did a better job on electrics. Being known for crappy wiring for more than 50 years is not exactly a good thing. I have seen the piano box in Rams trucks before, as well as the rectangle. Low bidder on the wiring harness proba...

It has a relay in that circuit. Dodge used a Power boxy that looked like a piano, with relays inside... https://www.factorychryslerparts.com/images/parts/Chrysler/fullsize/00i99257.jpg But they sometimes used a rectangular box with fuses, with relays behind it https://www.youtube.com/watch?v=Y4iF0jA...

So no clutch pull in with a jumper in the relay socket? You can check the clutch coil resistance from the relay socket. Starting on "volts" with your DMM, key on. Probe the relay socket for voltage to ground. The terminal with +12v is connected to the battery. So the OTHER terminal is the ...