This answer is more than a year late, but hopefully it might help someone. The problem could also be the power jack located on the back of the unit. It is a mini-USB 5-pin jack. My Garmin worked on the internal battery but not when the power cable was plugged in! There does not seem to be a guide for this specific repair, but I am quite sure that a jack replacement guide for another Garmin nuvi model, for example 1490T, which uses the same jack, will provide sufficient guidance.