I have a Rheem 15PJL48A01 heat pump which has been working correctly for years, and is maintained properly. It is hot here currently and so it is operating in cooling mode.
Yesterday and today, it has been very hot out. 105 °F yesterday and 103 °F today. The outdoor pump's fan has been cutting off every 20 minutes or so during the day. When it cuts off, it goes into a 5 minute delay cycle, then fires back up. During this time, the air handler (Rheem RHLLHM6024JA) keeps blowing air. There is power to the heat pump outdoor unit at all times. I removed the panel to investigate the shutdown code and it codes "5 min delay" and no other issue. Interestingly, at night when the ambient temperature cools off, the fan will run for hours without issue, blowing cold air through the home until the desired temperature is reached.
Here's a photo that shows the daytime shutoffs yesterday (Tuesday) between noon and 6pm as compared to the days prior. Notice that in the night and early morning it operates normally.
So what's happening? Is it overheating?