J-Walk

It is that electrical noise that is causing the problem. I purchased a in-line Ground Loop Isolator from Sonic Electronix for 12.95 with free shipping. It has good reviews and it worked for me. Easy to install at the Nav Control Box with the 3.5 mm jacks. Part # PAC SNI-1/3.5 (3.5mm Ground Loop Noise Isolator Works W/ iPod / Zune / iRiver and Others) Car Audio Stereo - Car Subwoofers - Car Amplifiers and Speakers Hope this helps.

Dave