Regulator & Brush Assembly - the combined voltage regulator and brush box fitted to Lucas alternators in the charging circuit. The unit mounts at the slip-ring end of the alternator, beneath the plastic end cover. It carries the carbon brushes that feed field current to the rotor slip rings, together with the solid-state regulator that holds charging voltage at the correct level regardless of engine speed or electrical load. Brushes wear down against the slip rings over time and the regulator is a sealed electronic module, so the two are supplied and replaced together as a single assembly rather than repaired. Worn brushes or a failed regulator typically present as no charge at all, intermittent charging, or a battery that is persistently over- or under-charged. The assembly can be changed with the alternator on the bench or in situ, without dismantling the rotor or stator.
