It often depends on whose air coil box the coach builder used.
Workhorse usually shipped the chassis with compressor, discharge line to condensor, receiver/drier with “one-time” quick connect (this allowed a possible pre-charged, chassis A/C system), and suction line with a “king valve” for connection to the block TXV.
Coach builder provided flexible liquid line from receiver/drier, evaporator (in air box with heater core), block TXV, and evaporator.
The suction port on our ‘02 was on the “king valve”.
FWIW - last year I realized the block TXV was installed upside down on the evaporator, thus feeding liquid refrigerant to the bottom/air entering side of the evaporator first. That’s backwards (you want the warmest air hitting the warmest refrigerant, or the coldest air hitting the coldest refrigerant).
I replaced the TXV with a new one, and while doing so, removed the “king valve” as it no longer served its intended purpose (and quite frankly, hadn’t since the coach and chassis were first built).
The “king valve” had the suction port on it - I just added an inline suction port into the flexible suction line as it headed back to the compressor, along with a port for the low suction pressure switch.
Pictures upon request.
‘91 Ultrastar Champion‘02 Georgie Boy Landau 8.1l Workhorse
‘03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad