hello i have been getting an intermittent battery light flicker on my 93 900turbo. i replaced the brushes and the problem persists. battery measures 13.5 with the car on and 12.5 off revving does not change the voltage reading. re did the connection on the small wire, the ground and power wires have continuity. tried tightening the belts still nothing. took the car to an auto store to have it tested and the battery is fine, the test said bad regulator? i was thinking maybe diodes but he said they tested ok. ordering a junkyard alternator as a last resort but i want to get some advice here before i go through with changing it out. anyone have any ideas as to what else i can test or look at?