Automatic Climate Control is not working?

Hey, I have similar problem like in this post:
https://www.2carpros.com/questions/no-ac-control-display#last

I have the car listed above LS and there is nothing on the climate control screen. Sometimes the red warm dual lights only light up (bottom right see attached picture). At night the light of some buttons lights up, but there is nothing on the display. One day, I started the car, the screen came on just for a sec and then nothing. When I tried to set the temperature, it turned off. So far, all the controller does is blow a little of hot air only (randomly). I turned the key to on. I measured voltage and on C5 and I got 3.15V. I checked the 10 fuse (was ok), but I changed anyways. I was trying to trace the brown wire from the cabin fuse box (Second picture). Measured voltage on third picture for C5 and I got the same reading 3.15V. I was trying to locate the S233 splice but did not succeed. I just have basic car wiring knowledge. I also unplugged the relays from the engine fuse box, I tested resistance and apparently, they are okay. Following this procedure: https://electrouniversity.com/how-to-test-a-relay-with-a-multimeter/

Finally, I was reading other posts, and I also have the same issue with the cruise control, (mirrors are working though).

https://www.2carpros.com/questions/buick-regal-2000-regal-cruise-amp-fan-system-stop-working-same-time

The post explains the reason is the ignition switch, but it seems a job for a professional.

Not sure what to do, to be honest.