The FM transmitter is programmed to reduce power when a car charger is plugged in to, I believe to stop the charger cable acting as a antenna and so boarding casting the signal outside of the vehicle.

However there is a script on either this forum or Nokia's own which overrides the power reduction and I have been using it without any issues for the last 6 months or more.

Found the link now but only do this if you are confident you know what you are doing as there is a danger you could mess up your transmitter


http://discussions.nokia.co.uk/t5/Ma.../755743#M18280