How can you tell when it is a starter or alternator that is the problem in a 1992 Mitsubishi Diamante what does it sound look or act like?

Answer

What is vehicle doing??

With a fully charged battery

Check voltage with a volt meter at battery at rest it should be around 12.75

With engine running volts should be 13.8-14.2 if in this range alternator is working

Check battery cables for looseness and/or corrosion

make sure that the current its getting to the starter solenoid i had a problem when i tried to start my car and the problem was the back part of the ignition switch it had a loose screw i fixed it and now it starts fine