I find that I use my microwave display to confirm IF I have 120 volt power to the van, I can look in through my side door and see it.
You may want to consider getting a tester ( or a surge device) so that you don;t hurt your van ($$$) by plugging into a bad source.
I have only seen this once but the wiring was incorrect in the "pedestal" at a campground.
https://www.amazon.com/s/ref=nb_sb_s...d=STUGWEAOAYZ0
I cannot recommend any particular product as i don't use them ( cause I use a volt meter), but you might benefit from a surge protector with indicator lights
or even these 2 devices
https://www.amazon.com/Power-Gear-3-...12ZZHZ37YY22AJ
https://www.amazon.com/Camco-55233-E...1M4RRV0SPZ7DWF
would allow you to check wiring polarity and ground are correct for $10
back to earlier GFCI- yours in probably by the sink in the bath- if it gets tripped it will likely kill outlets in the galley and outside ( my PW Lexor is wired like this) just an FYI if those outlets ever not work when you KNOW you have 120 volt power- check the GFCI reset button.
You may also want to have a look at your circuit panel so you are familiar for when you need it.
and a flashlight handy too
mike