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Glow Plug Testing and Replacement Instructions

Model: Volkswagen Polo MK III, Polo III, Polo 3, MK 3, 6N - Years 1994-2003
Part: Glow plugs

A glow plug is essentially a resistor that, when powered, becomes incandescent to pre-heat the combustion chamber and create optimal thermodynamic conditions for combustion and cold starting. To test its operation, simply check its continuity, even with a warning light: since the glow plug is screwed into the cylinder head and thus grounded, connect one end of the bulb's power wire to the positive battery terminal and the other to the glow plug. If the bulb lights up, the resistor is intact; if it does not light up, the glow plug is faulty and needs replacing.

Updated on 15 February 2026 by ScegliAuto

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