It Could be a Screw Loose on the Connector(s)at the Other end of the Power Cord.Either Way,You will see once you remove the cord clamp/holder.If the Screws are Not Loose,Then i Would Replace the Cord,cause there could be a broken wire.Just make sure it is the same Gauge wire,i would'nt recommend to go thicker in gauge wire,unless you want problems.Keep it the same and you will be ok.