Fixed a leak on a less than year old Trane unit, fired it up and watched it. Unit is on stilts so electrical is at head level. Right about the time I was going to take panel off and pull gages. BOOM! Contactor let loose. Almost made me soil myself because I was watching a payloader pass by and I of course was not expecting it. Sounded like a shotgun blast and shook the panel pretty good. Glad I had the panel on because The side of my head would have looked similar to the panel.
It just basically blew the contact points out for no good reason. Nothing major or massive burnout, just too close for comfort.Checked all electrical, changed contactor, monitored and left.
Stay safe out there