parrot phone kit

[dazsparks]

i wonder if anyone can help me, i have a transit 280 100hp 2003 i have fitted a ck3100 parrot kit in it. The kit works fine when the van is not running, but if some one rings when van is running all the other person can hear is interfearance or engine. Have swoped kit with my other transit same fault some one told me it could be alternator winde, sorry cant spell good , any ideas