2001 Ford Taurus 3.0 DOHC. Starting Problem

2001 Ford Taurus 3.0 DOHC. Starting Problem. When door is opened the interior lights come on, door dings, etc. As soon as the ignition is turned everything goes black all power is lost. Disconnect battery cable and reconnect, open door again and the interior lights come on, door dings, insert key and turn, everything goes black, car does not start. This cycle repeats over and over again every time the battery is disconnected and reconnected. I have replaced battery, ingition switch. The starter was replaced last year. Why does power blackout, and car not start when key is turned?

You have a bad connection somewhere in the main power bus to the ignition switch. If you haven’t cleaned the battery connections already using a battery post cleaning brush then start there. Check the wire that supplies power from the battery to the main power distribution panel under the hood and make sure that it is ok and doesn’t have any internal corrosion. Cleaning the ground connection from the battery to the chassis would be a good thing to do also. Verify that power is getting to the main fuse panel under the hood while the trouble is happening using at least a test light probe. If that area is ok then check the fuse that supplies power to the ignition switch and follow it until you find the fault in the wire connection.