STH control unit, component description

D83.70-1403-09

1 Stationary heater unit

N33/3 Warm water additional heater control unit

Location

The warm water auxiliary heating control unit is integrated in the stationary heater unit which is located at the vehicle underside between the left vehicle rocker panel and the vehicle tank at the level of the B-pillar.

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Task

The warm water auxiliary heating control unit is the master control unit for the following two systems:

 Stationary heater (STH) system, with code (H12) Warm water auxiliary heater.

 STH heater booster (ZUH) system, with code (HZ5) 10 kW warm water auxiliary heater with timer, which is called "Tandem heater booster".

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The warm water auxiliary heating control unit controls the following functions:

 Monitoring signal from temperature sensor (N33/3b1)

 Monitoring signal from flame sensor (N33/3b2)

 Monitoring signal from overheating sensor (N33/3b3)

 Actuation of blower motor (N33/3m1) of STH combustion air blower

 Actuation of glow pin (N33/3r1)

 Actuation of metering pump (M46/1)

 Actuation of circulation pump (M13/4)

 Actuation of vehicle blower motor (M2)

 Actuation of the red or yellow light emitting diode (LED) integrated in the warm water stationary heater switch (S46/11)

 Fault shutoff in the event of exceptional operating conditions such as flame-out, undervoltage or overvoltage or failure of internal coolant temperature detection

 Fault shutoff and fault interlock in the event of overheating

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 Communication with the warm water auxiliary heater 2 control unit (N33/2), with code (HZ5) 10 kW warm water auxiliary heater with timer or with code (HZ9) Heater booster, diesel

To do this, the warm water auxiliary heating control unit reads in the following components via discrete lines:

 Stationary heater radio signal receiver (A49/4), with code (HY1) Radio remote control for auxiliary heater

 Temperature sensor

 Flame sensor

 Overheating sensor

 Warm water stationary heater switch

 Warm water auxiliary heater 2 control unit, with code (HZ5) 10 kW warm water auxiliary heater with timer or with code (HZ9) Heater booster, diesel

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Moreover, the warm water auxiliary heating control unit reads in the following messages from the related components via the Controller Area Network bus class B (interior) (CAN-B):

 "VWZ_STH_MFL (timer status)" and "STHL_EIN_KOMBI (STH/ventilation On)" from the instrument cluster (A1)

 "T_MOT (engine coolant temperature)" from the coolant temperature sensor (B11/4) via the instrument cluster

 "T_INNEN_KLA" (interior temperature)" from the interior temperature sensor (S98b1), with code (HH9) Regulated air conditioning (Tempmatic), via the KLA control and operating unit (S98)

 "TEMP_SOL (specified temperature value)" from the KLA control and operating unit

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After evaluating the input signals and messages, the warm water auxiliary heating control unit actuates the following components for the control of the stationary heater unit via discrete lines:

 Blower motor of STH combustion air blower

 Glow pin

 Metering pump

 Circulation pump

 Blower motor of vehicle

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In addition, the warm water auxiliary heating control unit places the following messages on the CAN-B:

 "STH_EIN (STH switched on)" to the DEB control unit (N70), with code (LD0) Dome lamp with reading lamp at driver/front passenger, and to the KLA control and operating unit

 "STH_ZHZ_EIN (heater booster function is activated)" to the KLA control and operating unit and to the warm water auxiliary heater 2 control unit, with code (HZ5) 10 kW warm water auxiliary heater with timer or with code (HZ9) Heater booster, diesel

 "GEBLAESE_EIN (switch on vehicle blower)" to the DEB control unit, with code (LD0) Dome lamp with reading lamp at driver/front passenger, and to the KLA control and operating unit

 "ZWP_EIN (switch on additional water pump (circulation pump))" to the KLA control and operating unit