Usually behind the breaker panel or close by. Best to check output with a multi-meter.
Sometimes it's easier to check voltage at the battery. If the converter is working the battery should measure 13v+ if the converter is working. That would mean your RV is plugged into power (shore power of some kind), and the converter is charging the battery. Which usually indicates the converter is working.
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder