I installed an auxiliary input using these instructions here:
http://eurosportvr.com/misc/ipod%20input/index.htm

I'm getting a background noise sort of like a morse code type sound when the phone is plugged into the cigarette lighter and the Aux input. It's there whether the engine is running or not. I don't hear it when the phone is being powered off its battery, only when it's being powered by the car. I don't hear it on AM or FM, only Aux. I'm thinking it's using the audio cable as a ground? Is there a better place to ground the cable than the chassis of the radio like the instructions show? I'm sure a ground loop isolator will work but I rather use that as a last resort. Thoughts? Ideas?

 

Hhhmmmmm.... I think it may be a ground issue on the cigarette lighter. If I take a wire from the metal of the lighter socket to the body of the car the sound all but disappears. Where is it grounded from the factory??

 

i got the same problem with all my cars. If i use a MP3 player with a mini-stereo jack (3.5mm), and the MP3 player is charging thru the cig lighter, I get crazy loud noise. I never tried messing with adding another chassis ground to the lighter socket.
I think i might mess around with that tomorrow.