Check for no click when the relay is energized
Check for intermittent operation
Check for contacts stuck open
Check for contacts stuck closed
Check for excessive heat on the relay
Check for burnt smell or visible damage
Check for pitted, corroded, or discolored contacts
Check for inconsistent voltage at the load
Check for high resistance across closed contacts
Check for no continuity when the relay should be closed
Check for continuity when the relay should be open
Check for coil resistance outside specification
Check for open coil
Check for shorted coil
Check for loose, damaged, or corroded terminals
Check for vibration-related failures
Check for failure under load but normal operation with no load