Displaying coolant temperature, function - GF54.30-P-3020R

MODEL 230

Networking

Fig 1: Displaying Coolant Temperature - Signal Communication

Courtesy of MERCEDES-BENZ USA

Function requirements

Terminal 15 ON

Signal flow

The coolant temperature sensor (B11/4) changes its resistance according to the coolant temperature. (The sensor is an NTC resistor, i.e. its resistance decreases as the temperature rises.)
The resistance of the coolant temperature sensor (B11/4) is registered by the ME-SFI control module (N3/10).
The ME-SFI control module (N3/10) converts the resistance values of the coolant temperature sensor (B11/4) into a temperature value.
The ME-SFI control module (N3/10) relays this temperature value onto the engine compartment CAN.
The instrument cluster (A1) reads this temperature value from the engine compartment CAN and actuates the engine coolant temperature gauge (A1p1) accordingly. A warning message may also appear in the right multifunction display (A1p15).

Drive

The engine coolant temperature gauge (A1p1) is driven by a stepper motor.

Display of coolant temperature

This display is a plateau display.
This means that the needle remains at 96°C at temperatures between 96°C and 116°C. Temperatures within this temperature range are not critical. This strategy is intended to avoid arousing unnecessary concern on the part of the driver.
If a coolant temperature > 120°C is received, the display is limited to a maximum of 120°C. When the needle reaches the warning sector, the color of the coolant temperature warning lamp (A1e54) changes from white to red. At the same time the coolant symbol appears in the left multifunction display (A1p13) and the right multifunction display (A1p15) reads "Coolant: Stop, engine off!"

The system responds to a defective radiator fan by leaving the plateau display mode and reverting to a display that also shows temperatures between 96°C and 116°C.

Needle behavior

When the ignition is switched on (terminal 15 ON), the needle moves round to the display value within t = 1 s (PT2 damping at t = 0.12 s). When the ignition is switched off (terminal 15 OFF), the needle returns to the zero position and is damped (PT2 damping at t=0.5 s).

	Instrument cluster (IC), networking of components		GF54.30-P-0002-06R
	Instrument cluster (IC), location / task		GF54.30-P-3039R