1992 Peterbilt 379 HVAC system actuators and switches

Need a little help determining what this part is exactly and where to get one. I'll start by saying when I purchased this Pete about a year ago the AC in the cab blew ice cold. This winter it stopped working at some point and when the warmer weather rolled around I no longer had any ac at all. The controls had to be set to bi level or floor in order to not have air leaking behind the dash. I found where a fitting was bad in an AC line under the hood, replaced it, pressure tested it. Replaced the dryer. Recharged it and it blows ice cold again It's converted to 134-a from r12 being as old as it is and that was done before I got it. I start fixing the air leaks behind dash and quickly realize both actuators are bad and leaking. I order part DA 10000 and DA 10050. The first number is for the dual action actuator and second number is for the single action actuator. Once I replace those I am getting a leak from the male branch tee that's screwed into what looks like a block of some sort that also has what I think is a low pressure switch or binary switch?? Screwed into it as well. Please reference the picture for actuators and switch. The switch has 2 prongs and an electric wire to each and male thread screwed into the same block as the male tee branch that swivels and is in line with the single action actuator. This system is all controlled with air. The tee is what's actually leaking where one of the lines goes into the quick connect. The switch may be good but im afraid once I disconnect the tee or get proper air flow to it that it'll possibly fail as well and I want to replace it all while im in there anyway. Peterbilt said that it's probably the low pressure switch and if so it's discontinued.
My questions are is it a binary switch or low pressure switch? Are they different? What purpose does this switch serve? Do the controls and actuators run off of the 120psi in the truck or is it stepped down somewhere to run at lower psi? Does anyone know what size air line that Peterbilt used in 1992 for the air controls pictured? And where do I get a new assembly with switch and block and tee if possible lol?! Probably a long shot.

 

Peterbilt gave me Rd3-4084-1 for the discontinued part number for the "low pressure switch"

 

Pics coming

 

Here's the blower motor and cage for the sleeper ac. Installing this and the sleepers ac will be functional as well. Previous owner had it disconnected because it was bad.

 

Awesome information and I appreciate every bit of it. Huge help to me. There are 2 actuators, one dual and one single action. The single action has white air line to it and the dual has one grey and one red to it. Is that what you mean? Or are the more actuators somewhere else as well?

 

There's another switch that the dial behind the control panel opens and closes based on position. When the control is on ac the dial moves the switch and I can hear it click. And it clicks off when you move dial into a position that's not an. This switjc doesn't look like a pressure switch. It's got an arm on it that the dial pushes down to make contact. And it has 2 wires on it. The pressure switch you can see in the pic below the tee. I will take and add pics of the dial and other switch. Whete is the 3rd actuator located? Peterbilt told me there were only 2 actuators but I haven't given a very thorough look besides where my pics are taken.