I have a 120volt angle grinder which runs very hot under no load condi

A Hilti angle grinder, 120 volt, 5 inch disc type which runs very hot, burns out brushes and draws heavy amperage, 7/8 amps, under no load conditions. Have changed brushes, brush springs, tested armature windings with low ohm , Shallcross, resistance checker and also used a ‘growler' shorted turns detector, checked field coils for resistance matching and shorted turns with an inductance test. Armature and rim gear bearings in good condition and lubrication is good. Tool has an electronic torque control unit which also prevents tool activation if power is applied when the start switch is in the on state. It monitors armature revs. using a magnetic sensor and shaft mounted magnet assembly. This is an encapsulated unit using a 45 amp power mosfet device as the control element and the terminals are accessible, it checks out ok. Anybody out there experienced similar trouble with angle grinders. Have repaired quite a number of different makes and models over the years but never come across thisparticular fault.

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