At idle the voltage goes up to 15.1 Volts. I think it is a little high for the instruments and controls it should be close to 12 volts. Is there a voltage regulator beside the one in the alternator?

 

there is one inside the pcm engine computer.it tell the alt regulator how much to put out.but it very rarly goes bad i would do the alt first then the pcm last.also if you have a bad battery or if it has a bad cell the alt can act up.cheack the battery good first and the cables should be clean and tight.if you have to take them loose and wire brush them and reinstall

 

and it should charge at 13.4 to 14.2 max more than 12vt