how to fix my bluemedia bm6300?

I have a bluemedia bm6300 sat nav with no charger, but I have a couple of leads that fit, when I plug in a charger the red light comes on the top right of the unit, but when im pressing and holding the power button the unit does not turn on- it this because the charger may not be working properly or because the unit is knackerd?
Any help would be v much appreciated