Thermal shutdown? (ktp-445u)
 

So I'm running a ktp445u and have a problem recently, I suspect is temperature related, but want some 2nd opinions on. Last 2 days twice now the left channels cut out. I turned down volume both times and switched to an audio book. Been listening to 'off to be the wizard. ' anyways, today was a longer drive. A few minutes after the left channels shut down I was getting a pretty noticeable alternator whine from the left side. Then a while after that the left side came back. Startin the car after its been off for awhile I have yet to have this issue. Sound like thermal shutdown to y'all?

Ps: ACs been off during both occurrences

I have one and the right channel has shut down on me twice this past summer. I have mine tucked where the stock location is under the trunk covers. It would go dim/half power before it shut off. I assumed it was thermal shutdown because it was over 100f outside. My temp gauge said over 110f. I am running it 2channel x 45 watts. Considering running it at 2x90 but I read the stock speakers are already at 2ohms.

Yep sounds like thermal protection kicking in.
Try making some room around the amp for increased air flow or turn down the gain a few notches.