Alternator works when it wants to. Yesterday my car needed a jump because the battery died. While driving I noticed the volt meter was showing around 12.5. I get home and test the alternator and it was putting out 12.6. Ten mins later it was reading 14.7 and then back to 12.4. I thought it was wearing out so I replaced it. Today it's doing the same thing. Any ideas as to why? I am also now receiving OBII codes for low voltage on several systems.