I have a warn 9.5ti winch and I can hear the solenoid clicking, if I tap it with a hammer it will start working. Does that one solenoid need to be replaced?
Likely, yes. But before you buy a new one, make sure all the connections to and from the coil are good. Make sure all wire crimps are solid and there's no corrosion, and make sure it's got a good ground. If there's a weak connection, then it will kill the voltage driving the coil and keep it from engaging fully.