Spinning/buzzing/whining from engine compartment without the key in the ignition

Question

Hopped in my car one day, attempted to start it, no "engine turn over" at all, reminded me of when the battery is dead.

However, after "releasing the key" noticed an odd noise coming from the engine, like a spinning motor that won't start (kind of like a stuck on windshield wiper fluid motor).

Looking under the hood, appears the noise is coming from "the starter region" and the starter itself was getting very hot.

Disconnected the battery and the noise stopped. Noise continues even without the key in the ignition when battery is connected.

97 Honda Accord in this case.

Answer 1

After some research, appears common problems are "bad starter solenoid" or "bad ignition switch." I didn't attempt to diagnose the ignition switch as it turned out to be the starter.

In my case, banging on the starter with a hammer then reattaching the battery, the spinning noise went away. Until I tried to start it again, then once again it was "stuck" spinning again, but didn't actually start the engine. Until hit with the hammer again. Then stopped.

Turns out that a starter has "two" incoming electrical connections. One (the smaller one) engages the solenoid to push it in. As its pushed in it acts as a "switch" to engage the spinning mechanism (which uses the larger connection). So apparently the larger connection is "always on" on purpose. So if the solenoid gets stuck somehow and doesn't retract right, it could "still engage" the spinning mechanism even without the key in.

Theoretically you can check if it's an electrical problem by checking for continuity on the smaller wire. It should not be connected to voltage except when the key is on III.

So fix for me was replacing the starter. Works fine now. The power of duralast LOL.