I have the standard Intellitec latching relays.
I have had to clean the inside.
The relay should not hum.
Power should be applied to latch the relay. Then power is removed.
I am guessing the contatcs are corroded or pitted.
You can disassemble the relay and clean them.
I would also check to insure the power is disconnected from the relay coils. If it does not disconnect the switch could be bad. You can test by latching relay, then disconnect one of the wires from the small post. If the hum goes away your switch maybe bad.
Bud
USAF Retired
Pace Arrow
2003 Chev Ice Road Tracker