Polarity Checker

Oscar2

My van is fitted with a polarity checker and I see from posts many people use these. What do people do when they find the polarity is reversed? My van instruction book says this could harm electronic equipment but does not give any advice on what to actualy
do about the problem.....

I made up a extension lead where I reversed the live/neutral wires in one socket so ths swaps the polarity back.

Odd thing is that occasionaly the polarity warning light still stays on when I use this...in which case I just ignore it!