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Glow after the start, while the engine is running, reduces the white/blue smoke and reduces the cold start knock. The pre-heater system itself consists of self-regulating glow plugs, an electronic glow-control unit, and a temperature sensor. The self-regulating sheathed type glow plugs protect themselves against overheating, by limiting the current from the battery to the plug with increasing temperature. While the engine is running however, the voltage increases. Some glow plugs can burn out as a result. In addition, the plugs through which the current is passed are still exposed to the combustion temperatures after the start, i.e. are heated from the inside and outside. Sheathed type glow plugs capable of after glow can function at full generator voltage. Their temperature increases quickly, but is then controlled to a temperature, which is less than those of plugs which are not capable of after glow. This occurs through the heated control coil, whose electrical resistance increases while the current is reduced, so that the glow pencil cannot be damaged. The after glow time is usually made dependent on the engine temperature, because when the engine is cold the pollutant and noise emissions are particularly high. Therefore, in these cases the after glow time should be longer. |
