Alternator change

have a 2003 infiniti m45…was showing the battery light; co-worker tested with a ohm meter and the reading was 12.5(before stalling); suggested the alternator was bad. Just replaced the alternator and now the ignition won’t even turn over(dead as a door knob)…before the change, removed the battery(which is dead by now), followed the steps and now I’m dumbfolded…what could be wrong? please help

Someone did an improper “diagnosis”. There may have been nothing wrong with your battery. Don’t rely on co-workers to “suggest” anything unless they are mechanics.

You need to see a qualified auto electric mechanic to properly diagnose what is wrong. We cannot tell from here.

Do you have a good battery in it now? If the car is running the output of the alternator is usually 14 to 14.5 volts. A good battery should be at least 13volts when the engine is off. Now all this said, you need good clean connections to the battery, alternator, starter and good ground connections to the engine and chassis.

Check the circuit between the alternator and the battery positive post. Maybe a fusible link has given up. The co-worker has an ohmmeter so that should be a snap to do.

I’m a little confused by your post. I read it as you replaced the alternator but not the battery. You say you removed the battery and “followed the steps”. I’m not sure what you mean by that. Did you reinstall the old battery, in which case did you recharge it with a charger? Or did you install a new battery?