All lights flicker when car is running and when I’m driving, the car feels like the converter is shuddering pretty bad. When the car is off, the lights are fine. Replaced the battery and alternator. Has anyone had this issue before?

 

There are a few items that could cause the lights to flicker. I'd grab a volt meter and measure the battery voltage when the car is off and when the car is running.

 

Reads normal when off and when running it fluctuates a bit from 14.3 to 15.2 constantly with lights and AC off.

 

Was your car behaving the same way before you installed the new alternator and battery?

 

I believe so. Previous owner doesn’t know.

 

The previous owner's reponse is kind of suspect.

Look at the battery and find the manufacture date on it. Most manufactures have a round sticker with 2 numbers like 1/24 that means the battery was made in Jan 2024.

Look at the alternator to see if it looks new. A new alternator would be cleaner. Look for a sticker to see who made it and maybe it has a manufacture date as well.