Glow Plug: Description and Operation

Design
The pencil-type glow plug (R9) consists of a housing with female thread and an interference-fit glow rod. The heating element is located in the glow rod. It consists of a heating coil (b) and control coil (a) connected in series.

Task
Preheating prechamber or combustion chamber in order to achieve the temperature required for igniting the fuel/air mixture.

Function
When the preglow system is switched on, a current of approx. 30 ampere flows for each glow plug. The heating coil heats the glow plug. The control coil increases its resistance as the temperature rises and limits the current to approx. 15-25 ampere. The glow plug (R9) is thus protected from overloads.