Preheating system

The preheating system of the N47TU and N57TU diesel engines consists of the following components:

• DDE control unit
• Electronic preheating control unit
• Heater plugs (ceramic or metal heater plugs depending on type of engine)
• LIN bus as interface between the DDE control unit and preheating control unit

The first time the preheating control unit is switched on, the electrical resistance of the heater plugs is evaluated at the start of the preheating process. A heater plug that is already hot has a significantly higher resistance than a heater plug that is cold. If the resistance leads to the detection of hot heater plugs, the heater plugs are supplied with less energy at the start of preheating. If, on the other hand, cold heater plugs are detected, the heater plugs are supplied with the maximum energy at the start of preheating. This function is referred to as dynamic repeat preheating. It prevents a heater plug that is already hot from being overheated by a second preheating process that follows shortly after the first preheating process, thus supplying too much energy.

To check the preheating system, there are two adapter leads:

• 1-pin, order number 13 6 470
• 12-pin, order number 13 6 460