1990 Won't Start

My grandmother has a fairly new starter and her alternator,solonoid and battery are only a few weeks old. A few days ago her car wouldn't start so i cleaned the terminals and nothing. Her battery is good, but there is no power, no windows, lights, anything. The negative cable looks good so I changed the positive cable and still nothing. I thought that if the battery and alternator were good that the lights at least work. I have a Dodge Neon so they are different and my Mustang has never had this problem. Please let me know... Thanks!

Is the starter and the engine turning over? If nothing is happening then the starter may have gone bad. When you try to start the car do you hear a click? If not replace the starter solenoid again and see if that works. I would also suggest before doing anything that you check the wires at the starter. One of them could have come loose and won't let juice to the starter. If my memory serves me correctly, the starter solenoid is on the fender. Try jumping across the terminals to see if the starter will engage. If it does then the solenoid is bad. Use heavy insulated tools to do this as there is a lot of voltage going through to the starter. On a Ford product all voltage flows through this solenoid and if it is bad then nothing works. Finally, replace the ground wire from the battery. It could be bad internally and you would never see it. Hope this helps.