Engine coolant sender swith in a 1993 Chevy Blazer
 

Hello, while driving yesterday I noticed my temperature meter was not working. My mechanic friend changed the coolant sender switch. I drove for about 3 min. and the meter stopped working again. Went back to the auto parts store and exchanged the switch. Drove for about 40 min. and the meter stopped working again.
Just wondering what can be causing the switch to burn out?