DIAGNOSIS Concrete dust ingress is abrasive and can jam the hammer mechanism, overheat the motor, and cause switch failure.
FIX Use dry, filtered air. Remove the battery. Blow air into the vents, the chuck area, and the mode selector switch. Manually rotate the chuck while blowing. Do not use compressed air over 100 PSI. Do not disassemble the gear case unless qualified.
IF THAT DIDN'T WORK For persistent grinding or clicking, the hammer mechanism pins and springs may be packed with fines. This requires complete gear case disassembly, cleaning, and re-greasing with Milwaukee specified grease.
HEADS UP Never spray lubricants like WD-40 into the tool to clean it. This attracts more dust and can damage plastic and electrical components. Use only dry air or a soft brush.