AC clutch doesn't engage.

OMG you guys are going in circles.
Stop and check your clutch wiring, you do this with an ohm meter, digital is preferred.

It has to be at 2 ohms, if it is 0, then it is bad. If it is more than 5 it is bad.

 

It's almost always an easy fix, but the back and forth of the forum, and not being able to see in person adds a lot of challenges

 

I may be completely wrong as is often the case. I’m also lost on most electrical stuff. For some reason seems I recall the compressor being powered by a constant hot from the starter. That means the switching is done on the negative wire, Trace the hot, see if it runs to the starter, let me know if I’m right or wrong. Since you’ve checked just about everything. I would check the plug on the temp evaporator probe sensor. Located up above the blower motor resistor. Also check the single black plug on the resistor. I think it’s tied into the sensor. Any one of the 3 might have came unplugged. If so, compressor clutch won’t engage. As I recall it’s the single plug on the resistor that’s prone to getting unplugged. It’s a long shot, but a simple fix worth checking.

 

Check the resistance of the clutch to rule it out.

This is why I say check the coil resistance -

I think there is a path for power on the positive side that is switched, not on the negative side. if the OP checked the LP switch and then moved to checking the the path of power.

I think the following quote is close but it leaves out one important thing.

The relay

Freightliner uses a relay to switch power on and off to the compressor clutch. Even if there is voltage present at the plug without the compressor hooked up, that does not mean when there is a load there will be the same level of voltage when it is supposed to be engaging. The current load is low but with a bad relay (which happens) there will be a bad connection at the contact and this in turn will drop the voltage.

That said, I do not think this year of truck has the body module, which would not allow the unit to engage.

 

I’m guessing it’s a York style compressor. Always a problem with them. Clutches always burn up, usually takes the compressor bearing out with it. I’ve changed so many of them on both my Classics. Best to upgrade to a Sanden with the same type plug, get a new bracket, adapt the lines to fit. Throw the York in the trash.