Mack CXU613 A/C issues

‘14 Mack CXU613 day cab, A/C is freezing up on the low side from the compressor to the evaporator. Blowing EXTREMELY cold air (single digits) until it freezes up completely and shuts the compressor down. Hooked up gauges, both sides are low and don’t move a lot while it’s running (maybe 25-30 PSI, both high and low). Recovered Freon and got 2.551lbs out and it should hold 3.00lbs. Both compressor clutch and fan stay engaged the entire time, no cycling. Trying to find the expansion valve (or orifice tube?). Also want to check the thermostatic switch. Am I on the right track or should I be checking something else.

 

Yeah, pulled that out, and while it has a good amount of dust in it, it wasn’t slowing the air flow down...AT ALL! And the evaporator is really clean, although still really cold.

 

At least the cab side of it is really clean!