Hey gang!
Came back from a short 4 day trip with our FW and found the break away switch pin pulled. Luckily
for some reason it was not engaged. That could have been fun at speed having the trailer decide it was going to drag me to a stop on the E-way
Long story short the terminals had a gray slag looking corrosion on them so they would not make a clean contact. Only a little over 2 years old and stored indoors, I didn't expect to see that. - 2018 Sprinter
New switch has an LED on it to tell me if power is applied when I "test pull" the pin. (Reese brand from the local TSC)
FWIW here are some pics of the guts of one so y'all can see how they (are supposed to) work!
Note to self...check those switches!!!