Went to dealership a week ago with a dead battery. Car wouldn't start, would drive on while on Highway but pulling up to the light and stopping had it die. Got it jumped and to the dealer alright where they replaced the battery under warranty. I asked them about the alternator then which I was told it tested fine.

Then...

No check engine light came on on the way home or the next trip. Third trip, check engine light came on and said check charging system.

Fourth trip, going to get groceries, EVERY LIGHT started to come on, with a warning, one by one. Both GPS display and heads up display start turning OFF and then ON again after some time, one by one.

Power steering and brake system started to fail. Power steering for sure, was VERY HARD to turn the wheel. Got into the parking lot past the Firestation/Behind the bank/Home area.

Dies as I come to a stop.

Car lights turn on but engine won’t turn over.

The tow guy said he didn't think it would be the alternator and the dealership is has sent me a report saying, "Alternator Replacement, Start with replacing alternator, tested charging system and voltage was below spec at 7.5v with no loads when it should be at 14v at all times." I feel like they aren't even really sure.

I'm worried they didn't ground the car properly with the battery replacement and shocked the system/ecm. But really just looking for opinions and options right now, thank you.

 

Would clean up battery posts and cable terminals
Then follow negative cable to chassis ground and clean that point.
Check the engine ground strap and clean as necessary.
Inspect the wiring to and from the alternator to see none are frayed or have corrosion
If you do replace the alternator then be sure to clean the terminals

Good luck