Sounds like one or more diode in the alternator is shorting, could be from heat expansion, vibration or bad rectifier.
What condition was your battery in when you installed the new alternator? Batteries are the weak link.
If the battery is sketchy then it's possible the alternator won't be able to keep up with system needs and charge the battery completely. 12.2 v is too low. What is it in the morning before you even start the car?

 

I recently tested the battery and it still has 60% life. Last week, I replaced the 100A fusible link because it was blown as i forgot to remove the battery terminal. That time I checked the reading and it was 12.7 while car was off and around 14.4 while running.

 

ok, those numbers are much better

 

Test with a multimeter and found that the battery voltage reading about 12.2V while the car was running.

Check your alternator belt tension and make sure it is not slipping.

 

Belt testion is fine. I checked the voltage of the car this morning and it reads 12.7. so I am guessing the battery is fine and alternator is charging. So what caused the battery light to stay on for 30-40 min while driving

 

Did you get it scanned for pending or code history.

 

No I didn’t.

 

Alternator c an fail under load.
Measure alt output with full el ectrical load.

 

Basic scanners are pretty cheap, here, most auto parts stores will do a courtesy scan for free.
Also check the condition and quality of all the ground wires you can find in the engine bay. A questionable ground can cause the CEL to come on and with vibration and expansion the same ground connects and cancels the CEL.

 

Thanks for these suggestions. I really appreciate it

 

If you have an Autozone in your area, they will check the battery and alternator right on the car for free. Their testing equipment can put a load on the system to properly test alternator output.

Mike

 

He's in Australia, not sure AZ is global.

 

You could be over charging the battery with the alternator and tripping the light. Your high load operating condition when the light comings on (at highway speeds) would support this theory followed by the light going off during other low load conditions. Do you smell any sulfur-like odors (and indication you are boiling the battery due to over charging)?

Best advise as above have the battery and alternator tested as part of proof of theory.

 

You could be over charging the battery with the alternator and tripping the light. Your high load operating condition when the light comings on (at highway speeds) would support this theory followed by the light going off during other low load conditions. Do you smell any sulfur-like odors (and indication you are boiling the battery due to over chcharging?

I haven’t found any smell. I drove the car in highway (100km/h) with ac and radio after that night and no light came on. West to a auto part store to check they said everything is normal and it could be because of cold weather!!. Today while driving the battery light was flickering for a moment and goes of. The battery terminals are pretty tight. I am planning to change the alternator.

 

Update: Replaced the alternator and so far so good. Hope this solved rhe issue. Thanks everyone.