Hum in speakers...

Hi all,

"Mysterious hum" question here. I couldn't seem to find anything similar to this on the forum - maybe the electric-minded members could help me out.

I recently installed a pioneer touchscreen HU in my truck a couple of weeks ago, but I just noticed a high pitched hum in the speakers last night. It isn't noticeable at all when music is playing, but it is super obvious when listening to talk/podcasts. Symptoms:

1. It only happens when BOTH the headlights are on, and the display of the HU is on.
2. Turning off the display (the HU is still on and playing music, just turning the display screen off) with the lights still on makes the hum go away, so I assume it isn't a grounding issue ... but I'm no electrician.
3. When the display is ON, but the headlights are OFF there is no hum.
4. The hum happens on all inputs (ipod, bluetooth, radio)

 

did you only install a new HU and not mess with the speakers?
I would check the connections again at the plugs, especially the orange illumination wire since it appears to be connected with your lights. Since you have power the 12v lead and grounds sound good but I would also check them again.
make sure any unused wires are taped, capped or snipped to cover any exposed wiring which could make contact with another surface and cause the feed back.

 

Yep, I haven't messed with the speakers yet. I'll definitely check the connections again - I remember an unused dimmer wire (orange and white).