Cadillac Repair: 90 deville 4.5L, electrical

Question
Ihave a 1990 sedan deville w/4.5L ,just did plugs ,wires rotor etc. and was on a 300 mile trip ,car was running beautiful ,no error, previous or current of any kind when out of now were all eletrical shut down ( cruising at 60 mph ). now I am getting no eletrical power or readings anywhere.  Battery is currently
holding 13 volts, and no visable or uncovered fuse links appear shorted, no lights,radio,instrument at all, none

please advise, thanks Bob

Answer
Hi Bob,

     What you need to do is determine if the problem is with the power or the ground side of the circuits. What can happen is the ignition switch contact goes bad for one of the wires and then a major circuit will quit working. But that usually happens when the key is moved not just going down the road. Even though a fuse link looks good you still need to test it with eithor a 12 volt test light or a DC voltmeter to see if all the fuses are getting power. Then trace the circuit back until you find the problem. Otherwise maybe a ground for those circuits loosened up or corroded and you will need to trace the circuit back to the ground source. To trace the circuits you will need a good wireing diagram that can only be gotten from a Caddy Deville shop manual or from the alldata.com website. Otherwise getting the car to your mechanic would be best because without a hands-on there really isn't anything I can suggest to replace as a common failure. Bill