Stereo install issues

[madcow]

hi everyone, been a while since ive been around on here, but ive staggered back in need of help. I have installed an am/fm pod type radio and 2x 3' speakers onto my nomad. but now after around 5 mins the radio cuts out and gives a static type noise. the static noise is even present when I turn the unit off. after a while the radio will begin again if left on but will cut out again soon thereafter. has anyone overcome this issue? or happen to know where I should start looking? cheers.