For trouble-free starting of a diesel engine of a car at low temperatures, a HITACHI brand Relay, glow plug system is installed on it. A glow plug relay is an electrical device designed to activate the glow plugs in diesel engines, which in turn heat the pre-chamber. The activation of the relay depends on the signals from the on-board computer, which reads the coolant temperature and crankshaft temperature sensors. The relay is located under the dashboard or engine compartment. A large device that is not difficult to determine.

1. 124 Saloon (W124)
2. 124 T-Model (S124)
3. 124 Break (S124)
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The operational features of the relay of the glow plug system

The electronic relay unit receives signals to close and open the circuit. When receiving current from the control unit, the relay transmits it to the glow plugs. Along with this, there is a current-limiting resistor in the circuit, which also has a connection with the car's computer. Having received all the information about the state of the candles, it can turn them off.

It is very undesirable to allow a breakdown of the glow plug relay, it is important to determine quickly, and accurately what exactly caused the engine failure - the spark plugs or the plug relay itself.