2001 Prius - A/C light blinks

@ChapmanF Thanks, I just saw this reply now!
I did this and both times got the fast blinking. I heard it click when I moved the temp dial all the way to the left, but it didn’t cause the blinking to change.
I bought this car used in 2012 and haven’t adjusted the clutch.

 

Ok, so there's still no smoking gun. Couple choices:

1. Drive around until it fails again, use the same procedure immediately, see if you can get some codes then.

2. Spend the buck and twenty minutes to check and correct the clutch clearance just to cheaply eliminate that problem, and see what happens. If the problem isn't cured, see (1) or work through other things to check.

Full disclosure: the "buck and twenty minutes" for the clutch job assumes you have a few basic tools (like a socket wrench set and a socket for the engine under-cover screws and the bolt in the center of the clutch—if I remember right, those might even be the same size), and a couple measuring instruments: a basic caliper and a dial indicator. Not everybody has those lying around, but they're both super affordable (at the "Harbor Freight" level) and generally useful things to have around.