I parked my 2014 dodge grand caravan in May 2020 in my garage and 2 days ago tried to start it but it was dead. I assumed it was the battery so I charged it for 24 hours and I only got flashing dash lights.
I then tried to boost it and that turned the vehicle on but the flashing continued and the van was weak, engine trembled somewhat (shaked).
I called a guy to inspect it and according to his little diagnosing tool he said it is the alternator. Charged $80 for diagnosis.
Now I want to buy an alternator and have him replace it but he was not looking too sure that it was the problem. He said he is sure but you can tell he is not.
Do the symptoms I described sound as it could be the alternator?
Should I try any other tests before I buy the part and have it replaced?
PS. Should I buy a new or old alternator. The price is $300 new vs $150 used. Is battery replacement also neccesery?