I started taking my car to inspection but I noticed the volts were dropping until eventually the car died. When I used booster cables on another batter it read 13.5v and the car started. So its clearly not charging, and running off the battery.

I took alternator out and got it tested. All is good. I checked for bad connections and all is good. Put it all back in the car and no change. HOWEVER... 15 minutes later I start again and its reading 13.5v on the gauge, so for that one moment it seemed to be doing what its supposed to. Tried the next day, and back to just under 12v and not charging.

I'm out of ideas now. Could the alternator have an intermittent problem? Seems odd that when the store tested it (twice) it said it was ok. It has 3G connector. Brown FFR wire goes to light green on right of D plug. White middle connector goes to stator plug, left yellow wire goes to alternator post. The post then connects to battery via a breaker.

Any suggestions would be most appreciated.