I used a ground isolator from my local corner car stereo shop. It looks like a cylinder with two rca inputs and two rca outputs. It also has a ground wire but in our case it shouldn't be connected according to the dealer. I simply plugged it in between the 750fm & the audio out on my carputer & it worked like a charm.

Still waiting for word from armen on my returned 750fm for rma. Tracking says it is there, but he hasn't confirmed. I am really missing this unit!