Travvisd

What's up new to this forum but hoping to find some help and guidance.

I have a 87 Rx7 NA to t2 swap. But iv just recently had a problem with blowing my main fuse due to my alternator shorting out and causing a world of issues. My cars alternator has been swapped from s4 to s6 alternator the person who wired it before I bought it did it wrong which caused it to eventually fail. Of course as soon as I buy it.

Anyway i just got my new 130 am alternator and installed it and last night it was reading correctly..14.5 at idle and now for some reason today when I started it only reads about 13.2 at idle. My idiot light cluster does not work for some reason that I can't figure out. So I I wired in a inline light bulb from the (L) wire which is the light that goes to the cluster. And this did work last night. But for some reason is not working today. I'm really not understanding why the brand new s6 alternator is not putting out the correct voltage today, when last night it was putting out a constant 14.5 at idle. It is wired correctly and the belt tension is correct.
I'm thinking it has something to do with the idiot light cluster not working. iv taken it apart an found it to be in good condition.(no cold sober joints) and also checked the CPU and it too is in good condition. Also have checks all fuses ......what else could cause this to not work

If anyone has any experience with this could you please help me figure this out.