2003 buick century
 

Hi. All dash lights flicker off and on. Car won't turn over. Battery and alternator has been checked. They are good. A new starter was put in. A ignition switch and lock cylinder with key was also replaced. There's also a new starter relay that was just put in. Any ideas what to check next?

A known problem area is where the positive battery cable attaches to the battery. Look at the surfaces and you will usually find corrosion there.

There is a long distance between the battery and the engine, battery in rear of vehicle. Check the cables and connections , both ends of both cables.

yes I have checked and the battery cables are clear. The battery is fully charged. So there is no problem with battery or connection.