AC problem help please

There is usually one high side and one low side switch in the A/C system. Also some have a switch to turn on the radiator fan. The switch on the evaporator keeps the unit from freezing. It seems that you already know this. I would check for low gas, low air flow across the evaporator. But I would look at low gas and your pressure switches. Icing on evaporator could be caused by low gas or low air flow.

 

Is your fan coming on like it should?

If so, then I’m gonna say check the high pressure switch.

 

I had an expensive education on one of these once. There is a relay in the breaker panel for the compressor. Check and see if it looses control power to that relay when the clutch cuts out. I do not remember if the pressure switch is before or after if but you can chase it down.
The three switch control is a bit more than three switches. If gets signals back from the other switches and the blower motor. If it does not like what it is told it disconnects control power to the relay. The problem with mine was the blower motor but it blew just fine. I have the fuse- breaker panel that cost $650. Only used one time and I will make you a deal. Check it out and fix what is wrong.
Hope that helped and maybe someone else can.

 

Check the last thing that comes to mind, in this case its your ambient air temp sensor. Ive had them go bad and shut the a/c clutch off just like you describe, only when hot outside.

 

The A/C relay is the component that uses thes signal from the pressure switches to engage or disengage the compressor clutch, if your pressures are in spec and your pressure switches are not breaking the signal then your A/C relay is the likely culprit.

You can bypass the system and get the A/C compressor to engage by simply removing the relay and pushing a paperclip into the right terminals, that is easier for testing than running jump wires.

 

I know nothing about Freightliner a/c systems, but if the relay is the standard small box-like plug in relay it might be worth swapping it out to eliminate that possibility.