When I put my key in, the entertainment system and headlights turn on, and the dashboard lights on the ac system turn on. Once I start the car, the headlights turn off when switched on or or put on auto and the AC system buttons don’t show they’re on and only outside air flows through. The entertainment system also turns off once the car starts. Any advice on what could be causing this and how to fix it? This is recently purchased 2020 Hyundai Elantra.
Is the car not still under warranty?
Free repairs–under warranty–at the dealership were not successful?
Or did you purchase it “As Is, No Warranty”, from a non-Hyundai used car lot?
Any dash lights on, ie CEL or Alternator?
Any aftermarket electronics/alarm installed? They and the quality of their installation are often involved.
Any flood damage? That is harder to locate and fix, sometimes impractical economically.
Any CEL (Check Engine Light) or other warning lights when it’s running? Do those lights all come on when you first put in the key? And go out once the engine is running?
Your Hyundai has a 5 year 50K mile factory warranty to tne second buyer. I suggest you take the car to the nearest Hyundai dealer.