I hear you, believe me.I got to experience this last night myself.
I heard it blowing away in the garage while I was in the house watching TV. I took it in for the U73 fix the day before, but I don't think its related. We had triple digit temps yesterday and I'm sure the garage was at least 90. I plugged it in right away when we got home with 10% remaining. After about 20 min it was up to 30% when it got really loud. Since we didn't need to go anywhere right away, I just unplugged it and waiting for cooler temps in the morning.
But it is alarmingly loud. It is not a sound you feel good about coming from your $50k vehicle.
So, I bring the car into the dealer yesterday afternoon (so they can work on it this morning), and they tell me...oh by the way another recall is showing on your car. It appears to be the battery heater recall. UGH. 2 Software update recalls so far, and 1 physical device recall and the car was purchased in Nov. 2017. So far I have had more recalls on this car, then my last 2 cars in a WAY shorter timeframe. I hope this is not going to be the new standard. Also, the service person told me he has heard that Tesla's do the same thing with the fan when the engine gets hot...I think he meant the batteries, but who knows. He then proceeds to tell me that he has a BMW electric car and his car also does the same thing for 2 minutes. Hmmm...am I buying it....not yet. Waiting to hear from Chrysler why we NEVER had the issue prior to the software recall updates being applied. It cant be that hard for Chrysler to find out ALL the things that the software update "fixes". I guess we will see.
I will update when I hear back from the dealer (hopefully today). I am hopeful that ChryslerCares follows up with the dealer as well, as I gave them the case number that was assigned to me. Crossing my fingers for some positivity!