i just put a alternator on my car now it still wont start .. had my battery looked at n its good

All the alternator does is charge the battery. It will not prevent the vehicle from starting when the battery is fully charged. Measure the voltage at the battery with key off engine off. A fully charged battery should be about 12.5 volts. Measure the voltage at the battery with key on engine running and it should be 13.5 to 14.7 volts. Also the big wire going to the alternator should have battery voltage all the time even when the key is off. If there is no battery voltage at the alternator the cause must be investigated.

I am also having this problem I have a new battery alternator is good battery light came on few weeks ago I check it’s my alternator wire blew replaced it it’s been fine but car does not crank clicks even when battery is charged it dies over night or just will click unless hooked up to jump box

Okay i just changed my 2004 mercury lasble alternater and the car still want start do i have to have a half tank af gas in it to star the cat