Sprinter 3500 L5-2.7L DSL Turbo (2004)
Glow Plug Relay: Description and Operation
The glow plug relay supplies battery voltage to the glow plug through a timed cycle that is related to coolant temperature. The glow plug relay is located
under the battery. The purpose of a glow plug system
is to improve combustion for low emissions and to achieve easy starting at low temperatures.
When the ignition key is turned to the ON position, the glow plug output stage and pre-glow indicator lamp are actuated by the ECM. The duration of the
signal depends on the coolant temperature. The glow plug relay has processing that communicates with the ECM. If no data exchange occurs at the
triggering stage, the preheating is switched off after 2 seconds.
Start glowing is initiated when the key is in the start position. The glow plugs (R13-R17) continue to be supplied with voltage. This makes it possible to
stabilize the cold starting speed. (After glowing is initiated when the starter reject speed is reached).
After the engine starts, the ECM determines the afterglow period in line with coolant temperature.If no signal is received from the coolant temperature
sensor, afterglow is maintained for thirty seconds.
The following aims are reached by the afterglow :
-
Improvement in warming-up properties
-
Prevention of white exhaust smoke after cold start
-
Stabilizing of the cold starting speed. The glow plug output stage constantly signals the current operating state and faults. The following are faults
detected and transmitted to the ECM :
-
Open circuit at one or several glow plugs
-
Short circuit in the glow plug circuit
-
Relay fault
If the Glow plug relay detects an open circuit at a glow plug, it is stored and indicated only once the engine is running by the preglow indicator lamp
coming on for about one minute and a fault is stored in the ECM. If a short circuit, a glow plug output stage faulty or a temperature related switching off
of output stages is detected, the fault is stored and indicated immediately by the preglow indicator lamp
coming on. Once the fault is no longer current, the indicator is immediately switched off, but the fault is stored in the ECM. If the fault is constantly
current, the preglow indicator lamp remains on until the ignition is switched off.
