Alternator Issues

OP's alternator was replaced too.

 

He had 3 or 4 tests done originally (please refer to op's first post) and they all detected a battery failure and not an alternator failure and had him change the battery ...

Curious why the alternator failure was not detected at that time?
only after he replaced the battery, he was then told btw your alternator is also failing!

 

Thanks to everyone posting…it is appreciated. I am not sure why the test didn’t detect the bad alternator at first…I just wanted to be sure the new battery was good so I asked the technician to run the test again with the new battery. We were both surprised when this time the battery passed and the alternator failed. I think it is two separate tests but I am not sure although he always showed me what he was doing and explained everything as he was doing it…I always like a second opinion to make sure I am not being taken

 

I do believe approximately 13.5v at idle is normal and fine for a vehicle equipped with a smart alternator. Alternator voltage on a modern vehicle fluctuates with demand to reduce load on the engine and fuel consumption.