Diagnostic system for an electric heater of an air-intake manifold of a diesel engine

A diagnostic system for an electric heater (10) connected with an air-intake manifold (8) of a diesel engine, in which at least one remote-controlled (6) switch (17) is disposed between the vehicle battery (15) and the electric heater (10). The systems provides the monitoring the voltage (Vbatt) of the vehicle battery so as to detect variations ( DELTA Vbatt) in voltage associated with commands for closing and/or opening the switch (17), and the evaluation of the condition of the electric heater (10) based on the variations detected.