So glad I found this thread. Over the last 2 weeks our battery has died 3 times. The first time lights were left on so we just figured it was an old battery. I jumped it today, figuring I’d take it to auto zone for a free replacement because it’s under warranty. As it was sitting there idling a terrible loud intermittent noise came on. I heard it inside my house and ran out to the garage and instantly turned off the car. Inside the hood there was smoke and bad smell. We restarted it and everything was normal, got the battery replaced , oil changed, mechanic checked it out and couldn’t find anything. I brought it home and the sound came again, again with smoke from under the hood. We were worried this time so we towed it to local mechanic (thanks AAA for free towing.)
It sat at the mechanic garage all day, mechanic couldn’t get it to reproduce the sound. Tried driving it, idling it, tried with AC on, and AC off, then I came across this thread and told him.
I drove back to the shop and realized the hood was up. I closed the hood and within2 minutes , the sound started Again. Not sure why the closed hood made a difference? Airflow maybe? The mechanic said the smell was definitely a freon smell.
Anyway, went to auto zone, bought a relay switch for 8 bucks like you said, and it’s all fixed.
Mechanics had it there all day and couldn’t figure it out. You guys saved me thanks .