Chrysler 200 2011 Voltage Problems

[BabyFaceNelson]

TL;DR

Car running at 18v after replacing the alternator. What should be checked next without having to pay $200 for a diagnostic?

My car burnt out my battery and alternator so I replaced the alternator and now the stereo system is dead when the car is turned on and the alternator is running at 18volts

 

[anorlunda]

The voltage regulator should prevent that. Check it out.

Some voltage regulators are internal to the alternator.

 

[BabyFaceNelson]

The voltage regulator is in the PCM