I assume you are talking about the diode test when you got .033 volts AC at 1200 RPM?
If that is the case, then yes a diode has failed and you need to replace the alternator. This will cause your battery to fail and a new battery on a bad alternator would last about a week depending on the load and use.
The battery light simply means there is not sufficient voltage present so it is normally the battery or alternator so I think you have enough to feel confident that the alternator will fix this.
Let me know if you have questions. Thanks
Tuesday, September 17th, 2019 AT 1:43 PM