STH control unit, component description - GF83.70-P-4200LE

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MODEL 216.3, 221.0 /1 as of model year 09/YoM 08 with CODE (228) Stationary heater

Illustrated on model 221.0

Fig 1: Identifying STH Control Unit

Courtesy of MERCEDES-BENZ USA

Location

The STH control unit is integrated in the STH heater unit (A6) (model 216) or in the STH or HB [ZUH] heater unit (A6) (model 221), which is located in the rear area of the right wheel arch.

Task

The STH control unit has the following tasks:

Reading in of sensors and signals
Evaluation of input factors
Actuation of components

Reading in of sensors and signals

The input factors are read in with the following connections:

Direct line
Interior CAN

Direct line

The following signals and sensors are read via a direct line:

STH radio remote control receiver (A6/1)
Temperature sensor (A6b1)
Thermal fuse (A6f1)
Glow pin unit flame monitor (A6r4)

If a temperature of T = 125 °C is exceeded in the STH heater unit, the thermal fuse detects overheating and triggers the heater unit fault run-on process for approx. t = 120 s followed by fault interlock.

Interior CAN

The signals are read in by the STH control unit via the interior CAN.

The resulting functions are described in the relevant function descriptions (see block diagram or function schematic).

Evaluation of input factors

The input factors that have been read in are evaluated by the integrated microprocessor and the relevant components are then actuated.

Actuation of components

Components are actuated with the following lines:

Direct line
Interior CAN

Direct line

The following components are actuated via a direct line:

Combustion air blower (A6m2)
Fuel preheating system (A6r5) (with diesel engine)
STH switchover valve (Y16)
STH fuel metering pump (Y23) (model 216) or STH or HB [ZUH] fuel metering pump (Y23) (model 221)
STH radio remote control receiver

Interior CAN

The signals are transmitted by the STH control unit via the interior CAN.

The resulting functions are described in the relevant function descriptions (see block diagram or function schematic).

Variants

Gasoline version
Diesel version

	Wiring diagram for stationary heater (STH) control unit	Model 216	PE83.70-P-2101-99CAA
		Model 221	PE83.70-P-2101-99SAA