LCD display unreadable characters

I made a projects having arduino nano V3.0, LCD 16x2 display, a relay and a magnetic contact. When I power on the relay, magnetic contact turns on. If magnetic contact turns on then some unreadable character shows in the display. I cannot understand why? Is it for harmonics? How can I filter that?

I just went through this. Go here!
Thanks! to grumpy Mike

What has this to do with Audio?

// Per.