Weird Electrical Issue?
 

Hey there S community. Looking for some advice and knowledge, hoping to find someone who has had similar issues, and can steer me in the right direction. My S has random issues, radio will power off Then back on immediately when shifting it slowing down sometimes and will do so repeatedly. Dash lights will flicker when in high rpms also random. Also when cruise control and high beams are on, then I turn off high beams, the cruise control will turn off automatically. Recently replaced the alternator. What should I check next? Any advice, info is appreciated.

It seems that you have one too many issues rounded up together and it will be nice to have a bit of more specific info, clearing these up a bit.
For example the radio powering off-on randomly has nothing to do with shifting a gear down. Probably most likely the vibration of shifting down is affecting
the radio and is switching on/off. Could be a loose connection if you are lucky.

I would start from the only thing that it is not random and you can re-produce as an error.
By the way, are you getting an engine light on your dash by any chance? (yellow engine sign!)
Turning off high beam switches off CC at the same time. Try troubleshooting this bit first, you never know it might magically solve the rest of the issues you are encountering.

It looks like you will have more luck posting the highlighted subject above under electronics section. Give it there a try.
Sorry I couldn't be of more help!
Best of luck!

Strange electrical gremlins like this can sometimes be the result of a poor ground. Make sure you have clean connections at the battery, fuses, and body ground location.

My car had the same issues, i went months back and forth going crazy. Replaced my alternator 3 times and it still didnt fix it. REPLACE YOUR BATTERY GROUND CABLE/TERMINAL. Local auto parts should sell a 2g wire with the terminal attatched to it for under $7

He is the link to my thread so you can check the symptoms and actions i took
https://www.s2ki.com/s2000/topic/110...ter-lights-up/

Wow, you went through a lot just to figure it out. Probably the road I was about to go down also. Thanks for the heads up Ap2low. I'll do that, and check back to let you know if this also worked for me. Thumbs up!