If the accu says Hi I am Full on the test button , i say short REPLACE ancre(armature AND carbon brushes together. remember if you have short brushes and you are working professional every day with this tool your brushes are AGAIN be shorted in a few weeks . 4 brushes in a brushholder and be carefull with soldering on the realy expensive switch if to long heat on the contacts it will also defect . MArketing technical position numbers to buy on differend models can be possible ask your dealer for a cheaper deal because what realy needed is the armature and the brushes not that complete unit , its a milwaukee marketing option because of the price Unfortunately
23 66 1239 Switch Handle Kit


but this is a real solution

Panasonic has with this kind of Johnson brushmotor exactly the same problems with Ey 7441 model after a few years of using by heat dissipation internal thermical or not thermical shorting of wires of the armature it is highly audible by a piercing sound

14 46 2018 Carbon Brush Kit


and together with this 16 01 3010 Service Armature Assembly



look this JOHNSON kind of difference in the
changed way of wrapping armatures and the old way was good but the new way delivers more power but also heat and that will make the trouble look here the differences of the old and the new

Take an eraser or emory cloth and shine up the battery contacts and the contacts on the drill.