Non Bonneville related.....MAZDA CHARGING SYSTEM PROBLEM!!
 

After tightening the Alternator belt on a friend of mines car, i used my didgital voltmeter to see how much the battery holds, and what it charges at
With the car off it red 14.54 volts
With the car running it red 18.60 volts
Now i know thats WAY to much so i tried the multi meter on my bonneville
With it off it holds 12.20 volts, running it says 14.60 volts.... so i know its working correctly, obviously something is wrong with her cars charging system, because i know 14 volts to around 14.80 -14.90 is normal but 18.60 is way over charging...whats causing this???????? She says her stereo also sometime will cut in and out like its not getting enough power...but im thinking maybe its getting to much and all that.....so any ideas?

What year Mazda? For some reason Mazda seems to keep all their info a secret. I had a friend that had a 95 626 that constantly had a check engine light on. Plus whenever the doors were locked the alarm would go off 30 seconds later. :? He got rid of it when every shop and dealership he went to couldnt fix it.

:? ...Yikes...

its a 1988 626

any ideas?

The voltage regulator seems to be going bonkers. If it's internal to the alternator, remove the alternator and have it bench-tested. If it's a separate component, replace it.

okay thanks!