How can I tell if my float switch pump is having issues

Yeap sometimes although we use the same pump over and over again we sometimes have issues. The pumps we use are fantastic value for money and on the hole have proven to be super reliable for moving water but sometimes they just stop which would be exactly the right time to give us a call. 

I've added a picture incase your unsure what qualifies for a "please come and take a look at my pump"