intermittent noise,aftermarket head unit

[working on it]

I recently installed a new Pioneer head unit with CD,aux input, and a dedicated satellite radio tuner; everything works great except for a strange noise that comes and goes with some regularity.The noise(lasting about 5 seconds duration at a time), which is a cross between a buzz and a data stream transmission sound (almost like picking up your phone when a fax is coming through, but not exactly), occurs under certain conditions regardless of the music source...FM tuner,Sirius tuner,CD, or cassette player (auxiliary input).It never happens in the early morning drive @ 3:00-4:45 am, but almost always starts after about 45 minutes into my 3:30-5:30 pm afternoon commute. I take the same route, use the A/C on the same fan setting, and do not use the radar detector or any other device except for the headlamps ( the running lights are always on). I've noted that the noise will occur whether power lines or microwave towers are nearby or not, whether I'm braking or under acceleration or maintaining a steady speed, and is not triggered by signals or braking input. It is not an alternator whine; there is absolutely crystal clear sound when the intermittent noise is absent. There is no pop or thump when the unit is turned on or off, and there are no amps or subs in the system (bone stock, only the head unit and sat tuner are new).As I see it, the only common factor in all instances is the afternoon heat build-up on the dashboard top. For the past two weeks its been over 100 degrees, and even thogh my A/C puts out 38 degree air at the center vent, the dash top is hot to the touch.Has anyone experienced this noise or have any ideas about eliminating it? I have a replacement HU on the way, but I fear that the problem will still be there. I checked a lot of posts here and on other websites,but I don't see the exact problem described in any of them.Please help!

[mmmikkke]

I have a Pioneer head unit plus XM plus AUX and I have never had your problem. Sounds like it's coming through the IP bus cable. I'd try disconnecting it and just running standalone. That will help narrow it down to either the HU or to the Sirius unit or to the AUX adaptor.

[working on it]

Thanks for your reply,Mike.But the noise is now gone. After re-installing the Pioneer HU,by separating and insulating all power,grounds,output and input wires, and even insulating the underside of the dash, the noise problem still persisted.Then, I had a tranny shop install a shift kit and new solenoids in the 4L80E, the noise went away. I've driven 800 miles during the 4 days since then, and the sound is now flawless. My best guess about the sudden fix was that the bad solenoid(s) in the computer controlled transmission was the source of the "cross-talk" that the HU was picking up. ????

[thecraft]

That's really strange.

 

If it comes back, you could try a noise filter that goes in-line with your head unit's constant power lead, like this one. Just make sure you get one with a amperage rating higher than your head unit's fuse rating.