One glow plug looks the same as the next? Well off the mark: On closer inspection, glow plugs differ not only visually, but also in terms of the materials used and characteristics.
Using the standard alphanumeric code on NGK glow plugs, you can quickly classify each glow plug. Try it yourself!
The NGK code provides information about the specific characteristics of a glow plug. This includes the battery voltage and the material of the glow rod. (pdf, 163 KB)