A question about dash A/C replacement.....

Thanks for the replies. We were in a RV park in Bakersfield with plans to move on next day further south. I was interested in knowing about the warm air and thought a shot of R134a might do the trick. Yes, he used a manifold gauge set and when hooked into low pressure side.....the gauge took 4-5 minutes to get up to 70#.

High pressure line is accessible only with dog house removed. Did not want this. He went under coach and tried to move the compressor by hand. It moved, but slowly and he thought there was a restriction or no suction.

So, that is where we are now. Back home. A Chevy dealer would be my first choice...but I have to find one with a bay door large enough for a motorhome.

I am not wedded to a new compressor and hope something else, minor, is the problem. In case a new compressor is warranted...I wanted to know all the details involved.

Should have called JD! LOL

IF he connected REAL AC gauges, he would NOT have to even look or "fiddle" with the compressor to determine if it was "shot". IF the system was empty, 1 lb would not do much. IF the compressor was running that shows there IS pressure to engage the pressure switch. I would NOT trust his diagnosis, go to a REAL AC repair company. Doug

If you don't know what gauge readings the mobile tech got, there's no way to guess what might be wrong.
He DID connect what they call a Manifold Gauge Set, didn't he? A head with two gauges, a couple valves, and long hoses to connect to Suction/Low Side, Discharge/High Side, and the Refrigerant Supply? All A/C systems require an Expansion Device, which is where the Discharged refrigerant expands to absorb heat. GM and Ford used to always use an Orifice Tube. The heart of it was a little brass tube like a piece of ballpoint pen refill. It had a screen that could get clogged but beyond that didn't actually fail. Imports and Chrysler typically used a Thermostatic Expansion Valve (TXV). Those CAN fail (they stick) and no cooling. If that happens it needs a Valve and not a Compressor. I think you need a better diagnosis.
EDIT - Above assumes the Workhorse Chassis included the A/C. I'm not current on that but I recall that the chassis used to NOT include what's correctly called HVAC (Heating Ventilation Air Conditioning) and various aftermarket suppliers provided it. Frigette, also known as SCS/Frigette, was one but I think they went out of business, Evans TempCon another, and I'm sure there were more. That made it difficult to get service information and parts. Still, I think at least most of them used TXV, not Orifice Tube.
To answer your question:
If replacing Compressor, YES, change out the Expansion Device AND the Drier. You said "X-Valve" which is the same idea as TXV.
Come to think of it, if you can find the "Drier" and it's in one of the SMALL diameter lines, probably close to the Radiator and A/C Condenser, then you have X-Valve/TXV and the Drier is called Receiver-Drier. If it has Orifice Tube, you'll find a much larger (coffee can size) Drier and it'll be in the larger diameter lines and probably away from the Condenser. Usually called Accumulator, but it has the dessicant inside so it's in practicality an Accumulator-Drier. Best practice is to seal the ends of the open lines when the A/C is apart, then install a new "Drier" (whichever kind the system call for) then evacuate the system with a vacuum pump before recharging with refrigerant. Once the Drier's absorbed moisture, evacuation won't make the dessicant useful again. Evacuation will evaporate only moisture that got in while working. Moisture interferes with cooling, and it also reacts with refrigerant to create acid and corrosion inside the system.

My first piece of advice would be to find a Chevy truck dealer and get a second opinion.