My radio unit - Harmon Kardon with CD player and tape - will not turn on. (I just bought this vehicle).
I also get some kind of static very quiet noise from the speakers, you can barely here it, sounds like line noise.

The PO said the stereo worked intermittently.
I pulled the radio head unit from the dash, and confirmed that the constant power, and Aux have power and that my ground is good.

How do I test the amp? or the head unit?

If I give the head DC power and ground should it come on? Or does it rely on a signal from the amp to work?

My buddy says he has the same issue and replaced his amp, and everything worked again!

 

The amp relies on a signal from the head unit to turn on, rather than the other way around. I would start by trying to troubleshoot the amp first.

 

Check if the fuse on the head unit is OK and sits tight. You can apply 12V to the auxiliary feed. When you push the power button it should turn on as can be noticed at the lights and the LCD.

 

Had the same issue, replaced the amp and it has been working great even since. Really easy to change out.

 

Ok, I just changed out the amp with one from ebay, plugged it in (but did not bolt it down.
Put the stereo back in, but it still does not turn on.

I have good power and ground at the head unit.\

Any ideas?

 

Does your clock work properly?

 

Does the head unit turn on at all?

 

Clock? Its on, not sure if it tells the time. So many other things to fix! LOL

Head unit does not turn on.

I Just went to a Land Rover Addicts house (he as at least 9) and bought a head unit from him. Plugged it in and it works.
The old amp also works. So it looks like it was the head unit.