According to Dave Martindale :
" writes:

- Replace any 14AWG aluminum wire
- Replace any 20A breakers on 12AWG aluminum circuits with 15A
breakers

Do you actually have any 14 AWG aluminum? Was it ever used for branch
circuits? Similarly, was 12 AWG ever used for 20 A circuits?

I thought aluminum was always required to be 12 AWG for 15 A.

AFAIK, Al was _always_ up one guage for the same ampacity.
Eg: 15A - 12ga, 20A - 10ga

But it doesn't hurt to doublecheck. It was new, some electricians
goofed.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.