Bad ignition switch?

Recently replaced my clutch and truck has been running good. I probably have started it 10-12 times since I reinstalled the transmission. Battery is brand new and sits around ~12.4volts. Starter relay is working(can hear it click and tested with voltmeter for continuity). Starter and solenoid are working(removed from truck and bench tested). Solenoid is a little corroded/dirty so I will be rebuilding before I put it back in. I tried to start the truck and it cranked 2-3 times and then I heard a clunk. Now I get a low hum when I turn the key. The thing is even without the relay and starter installed in the truck it still makes this low hum. Clutch is working properly and disengages from the flywheel. Is this a bad ignition switch? Any ideas?

 

Checked the ignition switch. Both leads to the starter have over 12 volts. Still makes a whirring noise and almost sounds like water sloshing around. Kinda lost here. Could it he the battery? It is basically brand new and has sat for 3-4 months. Was starting the truck fine though.

 

Does it have over 12 volts while cranking? Could be a high resistance connection causing your issue. I’d leave a meter on it and set it for peak when cranking the starter.

 

Your idea of a little dirty and corroded in the solenoid are miles apart !

Is the hum when the ignition switch is in start or run.

Not much on the start circuit with the starter relay and starter removed The clutch start switch and the coils.

Quite possible the normal cranking noise the hum can not be heard.