| Description and Operation General The purpose of the glow system is to heat the combustion chamber before engine starting and during cold engine running. The glow system consists of one pencil-type glow plug per combustion chamber, a glow control unit, a glow indicator light and the corresponding electrical connections. The glow control unit and the glow indicator light are controlled by the ( PCM) . The PCM controls the pre-heating time and the post-heating time as a function of the coolant temperature and the engine speed. The lower the coolant temperature, the longer the pre-heating time. At coolant temperatures below -20°C, the maximum pre-heating time is 8 seconds. There is no pre-heating at coolant temperatures above 80°C. Post-heating occurs after a cold engine has been started, to improve combustion. This improves cold idling and reduces hydrocarbon emissions during the cold-running phase. At coolant temperatures below -20°C, the post-heating phase can last up to 30 seconds. There is no post-heating at temperatures above 50°C. Post-heating is stopped at engine speeds above 2,500 rpm, to protect the pencil-type glow plugs against excessive temperatures. 3 - Glow control unit on the bulkhead | 