What was found
ALTERNATOR WILL FAIL ABOVE 2500 RPM, LOW VOLTAGE LIGHT COMES ON AND THE VOLTMETER INDICATES BATTERY VOLTAGE. OPS CHECK DURING GROUND RUNS ARE NORMAL MAX RPM DURING GROUND RUN 2400 RPM. ALTERNATOR APPEARS TO BE RPM SENSITIVE. POSSIBLE CAUSE: BRUSHES NOT RIDING TRUE ON SLIP RING. OVERHAUL PROCESS MAY CONTRIBUTE TO PROBLEM. AN ADDITIONAN (2) ALU8521 ALTERNATORS FROM INVENTORY PRODUCE THE SAME SYMPTOMS, SN E113128 AND F043304. BOTH ALTERNATORS FAILED WITHIN 2 HOURS OF OPERATION. BOTH WERE O/H UNITS. (K)