A/C Stopped working on 2005 Ford E-350

A/C stopped working (fans is working but there is no cool air). Any suggestions on what to check first?

2 answers
If the blower motor works inside your truck and you hear the condenser fan blow in the engine compartment operate, I assume the compressor is engaging so I would start by checking the refrigerant charge which requires pressure gauges.
Check your refrigerant level