Disconnect the relay from power and remove it from the circuit if possible
Identify the relay coil terminals and switch terminals using the relay diagram or pinout
Set the multimeter to resistance mode
Measure the coil resistance across the coil terminals
Check for an open circuit or short circuit in the coil
Set the multimeter to continuity mode or resistance mode
Test the normally open contacts for no continuity when the relay is de-energized
Test the normally closed contacts for continuity when the relay is de-energized
Apply the rated voltage to the coil
Listen or feel for a click when the relay energizes
Measure continuity again across the switched contacts while the coil is energized
Confirm the normally open contacts close and the normally closed contacts open
Remove power from the coil and confirm the contacts return to their original state
Replace the relay if the coil resistance is incorrect or the contacts do not switch properly