Terminate heater operation function

W83.70-1171-79

1 ASIC data bus

2 "Max. cold" position

3 Position 

4 Defrost position 

A7 Base module (GM )

A12a2 Automatic air conditioning (AAC) control and operating module

A12s1 Blower switch

P2p1 Display of driver information system (FIS)

S1 Drive switch

S62 Auxiliary heater button

S63 Auxiliary heater on-off/programming button

S144 Left multifunction steering wheel button group

S145 Right multifunction steering wheel button group

A12s2 Air distribution switch

A12s3 Temperature selection switch

A21 Auxiliary heater control unit (ZHE)

A68 Switch module 4, master

A70 Switch module 13, rear wall

A79 Switch module 5, dash support

A84 Switch module 12, rear wall

B100 Interior temperature sensor

CAN 2 Passenger compartment CAN bus

P2 Instrument (INS)

 The heating mode of the auxiliary heater (ZHE) can be finished

 by the instrument (P2),

 by operating a button of the auxiliary heater or

 by the auxiliary heater control unit (A21)

If the heating mode of the auxiliary heater has been triggered automatically on vehicles with automatic air conditioning (code H07), then it is ended automatically when the engine coolant reaches a temperature of 60 °C or the conditions for automatic triggering are no longer met.

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Heating mode can be ended differently. If the heater is in the control interval, heater mode is ended immediately. However if it is in the combustion mode, the auxiliary heater control unit (A21) first initiates run-on mode, before the heater has switched off completely.

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Ending the heating mode by the instrument (P2)

Depending on whether the auxiliary heater (ZHE) is in continuous/timer or preselector heating mode, the instrument (P2) ends the heating mode if:

 the adjusted time for heating duration

 the adjusted time for the run-on duration

 the adjusted remaining time

have elapsed.

Function sequence

1.1 If the auxiliary heater (ZHE) is in continuous heating mode, it changes into run-on mode if the ignition is switched off or the ignition key is removed from the steering lock.

From this point in time onwards the auxiliary heater only remains switched on for the adjusted run-on duration as, after the run-on time has elapsed, the instrument (P2) places the message "auxiliary heater OFF" on the interior CAN (CAN 2).

If the ignition is switched on again within the run-on duration, the auxiliary heater takes up the continuous heating mode again.

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1.2 If the auxiliary heater (ZHE) is in timer heating mode, the instrument (P2), after the adjusted remaining time has elapsed, places the message "auxiliary heater OFF" on the interior CAN (CAN 2).

1.3 In exactly the same way the instrument (P2) places the message "auxiliary heater OFF" on the interior CAN (CAN 2) when in preselector heating mode the time of the adjusted heating duration has elapsed.

2 The auxiliary heater control unit (A21) is woken up by CAN activities on the interior CAN (CAN 2).

Upon receipt of the message it either ends the heating mode immediately or initiates the run-on mode.

Simultaneously it places the message "auxiliary heating mode inactive" on the interior CAN (CAN 2).

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3 Master switch module 4 (A68) is woken up by this message, which passes on the information contained in it via the ASIC data bus (1) to the buttons of the auxiliary heater.

The status LED of the auxiliary heater On/off/ programming button (S63) in the switch module 5 waistrail (A79) and, depending on the cab variant, the auxiliary heater button (S62) in the switch module 13 rear wall (A70) and switch module 12 rear wall (A84) are switched off.

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4 Simultaneously the instrument (P2) receives the "auxiliary heater mode inactive" and displays, after it has received and evaluated the message, the switch-off condition of the auxiliary heater by means of a corresponding text message for approx. 3 seconds in the display of the driver information system (P2p1). After this the display goes out again.

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Ending heating mode by pressing an auxiliary heater button

Depending on the cab variant, heating mode can be ended at any time and independent of any mode via

 the auxiliary heater On/Off/ programming button (S63) in switch module 5 waistrail (A79),

 the auxiliary heater button (S62) in the switch module 12 rear wall (A84) or

 the auxiliary heater button (S62) in switch module 13 rear wall (A70)

Function sequence

1 If the upper rocker of an auxiliary heater button (ZHE) is pressed, the built-in electronics send the message "auxiliary heater OFF" to the master switch module 4 (A68) via the ASIC data bus (1).

2 As the buttons of the auxiliary heater (ZHE) are entitled to be woken up, master switch module 4 (A68) changes from CAN-SLEEP or POWER DOWN MODE into NORMAL MODE.

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It receives the message and transmits, after it has evaluated the message, the message "auxiliary heater modular switch panel OFF" to the instrument (P2) via the interior CAN
(CAN 2).

3 If the drive switch (S1) is in position "circuit 15R", then the instrument (P2) is woken up by the message via the interior CAN (CAN 2).

Otherwise, i.e. the drive switch (S1) is in position "circuit 15 ON", the instrument (P2) is already activated and can evaluate the message immediately.

After it has received and evaluated the message, it places the message "auxiliary heater INS OFF" on the interior CAN (CAN 2). Simultaneously it shows the switch-off condition of the auxiliary heater in the display of the driver information system (P2p1) by means of a text message for approx. 3 seconds.After this the display goes out again.

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4 Via the interior CAN (CAN 2) the message "auxiliary heater INS OFF" reaches the auxiliary heater control unit (A21).

Depending on the operating condition of the heater and upon receipt of the message "auxiliary heater INS OFF", the heating mode is either ended immediately or the run-on mode is initiated.

Simultaneously the auxiliary heater control unit (A21) places the message "auxiliary heating mode inactive" on the interior CAN (CAN 2).

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5 This message in turn is received from master switch module 4 (A68) and passed on the ASIC data bus (1).

Via the ASIC data bus (1) all the buttons of the auxiliary heater receive information about the switch-off condition of the auxiliary heater (ZHE).

The status LED of the auxiliary heater On/off/ programming button (S63) in the switch module 5 waistrail (A79) and, depending on the cab variant, the auxiliary heater button (S62) in the switch module 13 rear wall (A70) and switch module 12 rear wall (A84) are switched off.

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Ending the heating mode by the auxiliary heater control unit (A21)

The auxiliary heater control unit (A21) ends the heating mode:

 in case of heater overheating

 with undervoltage and overvoltage

 in the event of flame-out or flame monitor defective

 on GGVS [German hazardous goods road transport regulations] vehicles when the engine is switched off

 when the power take-off is engaged

 in the event of a discontinuity in the interior CAN (CAN 2).

Operating procedure

1.1 The auxiliary heater control unit (A21) requests the current interior temperature and the specified temperature adjusted on the instrument (P2) every 15 seconds via the interior CAN (CAN 2). In this way it checks constantly whether communication is possible via the interior CAN (CAN 2). If the communication is interrupted, it immediately triggers, depending on the operating condition, the malfunction run-on or a malfunction shutdown.

1.2 Furthermore, the auxiliary heater control unit (A21) receives information on the vehicle equipment (GGVS, power take-off) via the interior CAN (CAN 2).

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It needs this in order to end the heating mode when parking the vehicle or when switching on the power take-off.

1.3 Internally the auxiliary heater control unit (A21) monitors the combustion mode of the heater as well as the temperature in the heater. If the auxiliary heater control unit (A21) detects a malfunction in heating mode, for example heater overheating or flame monitor defect, then depending on the type of malfunction it immediately triggers a malfunction shutdown with subsequent fault interlock. The heater cannot be restarted.

2.1 If the heating mode has been ended by parking the vehicle or by switching on the power take-off, then the auxiliary heater control unit (A21) places the message "auxiliary heating mode inactive" on the interior CAN

(CAN 2).

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2.2 If heating mode has been ended due to a fault, in addition to the message "auxiliary heating mode inactive" the auxiliary heater control unit (A21) places the message "auxiliary heater not ready" and a message with corresponding fault message on the interior CAN (CAN 2).

3 Master switch module 4 (A68) is woken by the message "auxiliary heating mode inactive" which passes on the information contained in it to the auxiliary heater buttons via the ASIC data bus (1).

The status LED of the auxiliary heater On/Off/ programming button (S63) in switch module 5 waistrail (A79) and, depending on the cab variant, the auxiliary heater button (S62) in switch module 13 rear wall (A70) and switch module 12 rear wall (A84) are switched off.

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4 The instrument (P2) is woken up simultaneously and receives the corresponding messages.

Depending on the reason for switching off, it shows the switch-off status of the auxiliary heater or the malfunction in the heater operation in the display of the driver information system (P2p1) by means of a corresponding text message.

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Ending of automatic heating mode

 Only on vehicles with automatic air conditioning (code H07), when the heating mode has been triggered automatically.

Heating mode of the auxiliary heater which was triggered automatically can be ended, if

 the coolant temperature reaches 60 °C,

 automatic mode of the automatic air conditioning (KLA) is canceled,

 defrost mode of the automatic air conditioning (KLA) is canceled or

 the temperature selection switch (A12s3) is turned into the "Max. cold" (2) position.

Function sequence

1 If the temperature selection switch (A12s3) is turned into the "Max. cold" (2) position or the defrost or automatic mode of the automatic air conditioning (KLA) is canceled, the automatic air conditioning control and operating unit (A12a2) sends the message "Automatic cut-in not permitted " to the auxiliary heater control unit (A21).

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2.1 If the auxiliary heater control unit (A21) receives the message "Automatic cut-in not permitted", then it sends the message "Do not request ZHE automatic cut-in" to the instrument (P2).

2.2 If the auxiliary heater control unit (A21) detects that the coolant temperature is higher than 60 °C, then it likewise sends the message "Do not request ZHE automatic cut-in" to the instrument (P2) via the interior CAN (CAN 2).

3 The instrument (P2) receives the message "Do not request ZHE automatic cut-in", and as a result of this sends the message "auxiliary heater INS OFF" to the auxiliary heater control unit. Simultaneously it shows the switch-off condition of the auxiliary heater in the display of the driver information system (P2p1) by means of a text message for approx. 3 seconds. After this the display goes out again.

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4 Via the interior CAN (CAN 2) the message "auxiliary heater INS OFF" reaches the auxiliary heater control unit (A21).

Depending on the operating condition of the heater and upon receipt of the message "auxiliary heater INS OFF", the heating mode is either ended immediately or the run-on mode is initiated.

Simultaneously the auxiliary heater control unit (A21) places the message "auxiliary heating mode inactive" on the interior CAN (CAN 2).

5 This message in turn is received from master switch module 4 (A68) and passed on the ASIC data bus (1).

Via the ASIC data bus (1) all the buttons of the auxiliary heater receive information about the switch-off condition of the auxiliary heater (ZHE).

The status LED of the auxiliary heater On/Off/ programming button (S63) in switch module 5 waistrail (A79) and, depending on the cab variant, the auxiliary heater button (S62) in the switch module 13 rear wall (A70) and switch module 12 rear wall (A84) are switched off.

W83.70-1167-79

Shown on "Webasto" Air Top 3500 heater

1 Heater unit

2 Combustion and heated air blower

3 Temperature sensor

4 Glow pin/flame monitor

5 Burner insert

6 Overheating sensor

7 Afterburner pipe

M16 Fuel metering pump

HE Heater inlet

HA Heater outlet

V Combustion air inlet

A Exhaust gas outlet

8 Heat exchanger

A7 Base module (BM [GM])

A21 Auxiliary heater control unit (ZHE)

B100 Interior temperature sensor

CAN 2 Passenger compartment CAN bus

Ending of heating mode in combustion mode

If the auxiliary heater is in combustion mode, the auxiliary heater control unit (A21) first introduces run-on mode upon receipt of the message "auxiliary heater OFF":

1 The fuel delivery is interrupted immediately by switching off the fuel metering pump (M16).

2 The combustion air blower and hot air blower (2) continues to run for a short time at maximum speed, before it is actuated for approx. 35 seconds with 1/4 of its output.

In this time it cools the combustion chamber and flushes out the combustion gases.

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3- As soon as the flame monitor (4) detects "Flame out", the combustion and hot air blower speed are increased to maximum speed for 60 seconds.

After this the speed of the combustion air and hot air blower (2) are reduced in stages to "zero" during the next
60 seconds.

All the components of the heater (1) are switched off after the run-on mode has finished.

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Ending heating mode in the control interval

If fuel has still not been delivered or the heater (1) is in the control interval, the heater (1) is switched off immediately without going into run-on mode beforehand.