We have just gotten a 2005 Equinox for our daughter.... I noticed today for the first time there is a strange humming noise when the key is on (even when the engine is off). I cannot find source of noise.... I have even turned off radio/CD player and the noise is still there..... any ideas? I have placed a :15 video of the noise here.......... https://www.youtube.com/watch?v=PMNR...ature=youtu.be

I think I found source of noise.... I pulled fuse of the radio and noise went away...... but I still don't know what is wrong........................

Is it the sort of high-pitched sound in the video? If so: It is a cooling fan for the radio/nav unit that isn't heard over the sounds of the car running.

For fun: Drive it around normally, turn the radio on with the volume all the way down, stop, shut the car off, DON'T open any doors.

Is the sound there? (I'm guessing "yes")

Now open the driver'* door.

Is the sound gone?

The only time it makes the sound is when the key is on at least to the ACC position.... the second I turn the key off the sound goes away...... I removed the fuse to the radio and the sound went away too..... I'm thinking there is a problem with the amplifier.........................

The sound must not be coming through well in the video. It sounded like a fan to me. I still wonder what happens if you do my test:

I have ... Does not do it....only when key is on.

Weird. If it is related to the radio it should stay on after you shut the key off like the radio does.

Replaced the radio this afternoon and the noise is still there..... I wonder if it'* an "amp" that is making the noise...........................

You could try removing fuses until the sound goes away.

That is what my original post states..... When I pull the radio fuse the sound goes away.... it has some thing to do with the radio circuit but in replacing the radio the sound remains....