Proper metod to troubleshoot AC system for 01 Dodge 2500 360

That's just it... your pressure is still low. When you're as low on refrigerant as you are, you usually have to jump the low-pressure cutoff switch to get enough run time from the compressor to suck in the charge. Pull the electrical connector off of the accumulator, and jumper the two terminals (on the connector, not the switch itself) to each other (short piece of wire, paper clip, etc.).

The real question is... what caused you to lose so much refrigerant in the first place? Unless you fix the root cause, you're going to be back at this again - probably sooner rather than later.

You should read through the directions in the kit. It sounds like you tried to charge the system without the a/c turned on. If you have a can of refrigerant hooked to the system there will be enough pressure in there to close the low-pressure switch. Don't worry about that.

Air conditioning systems aren't really an off-the-cuff affair. You have a leak somewhere. The kit you bought will probably get your system working, but you're going to be adding refrigerant again soon if you don't fix the leak. You'll also probably overload it with oil if you keep adding it.

Nope, there isn't. I just did this on a friend's '00 Durango last week, that had leaked out it's entire charge over this past winter. I had to jump the low pressure switch before the compressor would even engage at all.