When diagnosing the cause of the engine starting problem, open the car door and observe how the brightness of the interior lights changes.
The brightness of a lighting lamp depends on its supply voltage.
During normal starter operation, the brightness of the interior lighting decreases slightly.
If the brightness of the lighting does not change, then the cause of the malfunction is usually a break in the starting system control circuit.
If the lighting goes out almost or completely, the cause of the malfunction is most likely a short circuit or breakdown to ground of the starter excitation windings or a faulty battery.
Don't tap the starter! In the past, it was not uncommon to see a technician tapping on the starter to try to figure out why it wasn't working. Often, under the influence of impact loading, alignment or displacement of the current collector brushes, rotor and bearing liners occurred. In many cases, after a blow to the starter, its functionality was restored - even if only briefly.
However, most modern starters use permanent magnets, which are fragile and can break if the starter is hit. A broken magnet disintegrates into several weak magnets. In some early permanent magnet starter designs, the magnets were glued to the stator housing. When the starter was hit hard, these magnets would fly apart into pieces, which, when they hit the rotor or bearing seats, would render the starter completely unusable.
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