Bosch WTA34 Series Setup guide

REPAIR INSTRUCTIONS

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TUMBLE DRYER

Vented WTA34.. / WTA35..

I. SAFETY INFORMATION Page 1

II. OPERATION Page 1

III. DESCRIPTION OF FUNCTION / TECHNICAL INFORMATION Page 2

IV. CONSUMPTION RATES / ENERGY REQUIREMENT / OTHER DATA Page 6

V. REPAIRS Page 7

VI. SUPPLEMENTS Page 13

I. SAFETY INFORMATION

Before commencing repairs, ALWAYS disconnect the appliance from the power supply!

If tests have to be performed while the appliance is live, ALWAYS use a residual-

current-operated circuit-breaker! When repairs are complete, perform a function test, as

well as a safety test in accordance with VDE 0701.

1. Safety test in accordance with VDE 0701

•Plug in the tester mains plug.

In the case of switchover models connect L1 and L2 on the tester.

•Switch on the appliance (door must be closed).

•Perform the test.

II. OPERATION

1. Selecting the programme

•“Cottons/coloureds” Turn the programme selector in a clockwise direction to the

desired drying setting (6 automatic drying settings).

•Easy-care Turn

the programme selector in an anti-clockwise direction to the

desired setting (5 automatic drying settings).

•Timed programme Turn programme selector / time switch to the desired time.

2. Buttons

•ON/OFF Switches the appliance on / off.

•“Low heat” For delicate textiles. The temperature is reduced.

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•Signal Button

pressed (LED on) – signal emitted in the “anti-creasing”

phase.

Changing

e v

olum

e – h

old

n t

e b

utton

, t

e s

igna

l c

hanges

When the button is released, the volume has been changed

and stored.

Switching off the signal – press the button again (LED off).

•Start time* The start time can be specified from 1–19 hours. The running

time is indicated by a flashing dot in the 7-segment display.

The “anti-creasing” phase is extended to 8 hours.

If the Start button is pressed, the appliance starts immediately.

If the door is opened during the preselected time,

the Start time LED flashes, press the Start time button again –

the LED switches to a steady light.

* Optional (WTA3480; WTA3500)

3. Programme progress indicator

Dampness in the washing is continuously checked by the electronic sensor system.

The programme status is displayed by an LED.

III. DESCRIPTION OF FUNCTION / TECHNICAL INFORMATION

1. General information

The

design is based on a fully electronic solution. All control functions are combined on the

power

module. The selected drying setting is

determined by a conductivity measurement.

The conductivity measurement of the washing is converted to a voltage measurement.

Sliding contact

earth

Washing

resistance

Sliding contact

driver electrode

Sliding contact

driver electrode

Insulation

Slipring

Drum wall

Input

Micro-

controller

+5 V

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•Operating and display module is situated in the fascia.

•Control and power module is situated on the right frame support.

•Thermistor sensor for measuring the air temperature.

•Condensation

pump is situated in the base group underneath the belt tensioning device.

•Motor is situated on the right in the base group.

•Heater on the rear panel – under the heating duct cover.

•Bimetallic thermal cut-out (>170 °C) is situated directly on the heater.

1.1 Operating and display module

The

operating and display module is used to input and output

information. It houses all the

direct input buttons, all signalling elements, e.g. LEDs, selector switches and signal

transmitters. Models are encoded by breaking off the side bridges.

1.2 Control and power module

The module houses all the significant components, e.g. micro-controller, relays, power

supply, etc. It performs complex functions with respect to controlling drying sequences,

monitoring the temperature, ascertaining parameters and actuating the operating and

display

section. The appliance is switched over from 16 A to 10 A by means of a wire jumper

Wire

jumper closed 16 A – Wire jumper open 10 A. Control and power module

≥

mask V 4.00

(software

version is indicated on the processor) changes automatically from 16 A to 10 A.

1.3 Thermistor sensor for measuring the air temperature

Thermistor

sensors measure the temperature of the process air at three dif

ferent points

the appliance (NTC thermistor – NTC stands for Negative Temperature Coefficient).

NTC R3

is situated in the ring insert under the door and measures the exhaust-air temperature.

NTC R4

is situated in the air current in front of the heater.

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Resistance values NTC R3 / NTC R4

Temperature

°CResistance

kΩ

25 9–11

60 2.3–2.7

NTC R2

situated above the heater and measures the temperature

of the process air blown into the

washing.

Temperature

°CResistance

kΩ

25 18–22

60 4.5–5.5

1.4 Motor

The motor drives the drum and the fan.

Specifications:

Rated input when appliance empty: 140 W

Current input when appliance empty: 0.5 A

Motor capacitor, capacity: 11 µF

Nominal frequency: 50 Hz

Nominal voltage: 230 V

1.5 Heater

The heater consists of two heating coils E2, E3, the bimetallic thermal cut-out B9 and the

NTC R2.

Heat setting 2: 1200 W

Heat setting 3: 1800 W

1.6 Bimetallic thermal cut-out (heater)

The

thermal cut-out should respond when localised overheating occurs, e.g. if the air flow or

electrical temperature control fails.

If a fault occurs, the thermal cut-out must be manually actuated by pressing the red reset

button.

Response temperature: 160–175 degrees Celsius

1.7 Door switch and safety functions

All

relay activations are controlled via the door switch.

When the door is open, relays cannot

be activated.

When

the door is closed and the mains switch is on, the capacitor is charged via a processor

output. Its voltage is monitored by an analogue input.

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When the door is opened, the capacitor is discharged. If a voltage of less than 1.5 V is

measured

on the capacitor when the machine is switched on, either

the door was opened or

mains failure lasted too long while the appliance was switched of

f. The programme must

then

be restarted. If the voltage on the capacitor is still suf

ficiently high, the programme is

reset and restarted following a voltage interruption.

Door switch F1

Closed Open

Micro-controller

Output

Analogue input

2. Principle of heating control

As the heater consists of 2 phase windings which operate at different power levels,

a different heating control can be used at various heat settings.

Heat setting 0 = OFF

Heat setting 2 = E3

Heat setting 3 = E2 + E3

The heat setting which is active is dependent on the programme sequence and on the

temperatures behind the heater (NTC R2) and on the drum outlet (NTC R3). If the motor

rotates in an anti-clockwise direction, the current heat setting is reduced by one

(Heat setting 3 ⇒Heat setting 2 or Heat setting 2 ⇒Heat setting 0).

Max.

Min.

Heat

setting

The maximum heat settings and minimum temperature values (NTC R2, NTC R3)

permitted for a programme section have been defined in the drying programme.

Both temperatures are monitored in parallel, the reset temperature having higher priority.

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the maximum temperatures

are exceeded and Heat setting 0 has still not been reached,

the heater setting is reduced by one and is maintained for 20 s.

During this time the temperatures are monitored. If they do not drop below the maximum

values, the heat setting is reduced again. Conversely, the heat setting is increased if the

temperatures

drop below one of the minimum values and the maximum heat setting has still

not been reached.

Min.

Max.

Limit

Heat

setting

3 or 2

the temperature limit is

exceeded, all heaters are switched of

f. The heater is not switched

again until the temperature has dropped to

min. If the temperature does not drop below

the temperature limit within 10x30 sec., the drying process is terminated and an

“Overheating” error message (extra dry LED) is output.

IV. CONSUMPTION RATES / ENERGY REQUIREMENT / OTHER DATA

1. Energy-efficiency class “C”

2. Energy consumption

Spin speed in r.p.

Approx. values Drying time in minutes

(including 4 min.

cooling-down Approx.

time) values

Energy consumption

in kWh

Approx. values

“Cottons/coloureds”

4-5 kg Cupboard dry

Iron dry

1400

800

1400

800

(10/16A) 75/55

(10/16A) 105/80

(10/16A) 55/40

(10/16A) 77/58

2.4

3.3

2.4

2.5

Easy care 2 kg

Cupboard dry 1.000 (10/16A) 31/27 1.0

The indicated consumption values are guide values which have been determined under

normal

conditions. Fluctuations up to 10 % are possible. Low ambient temperatures in

the

installation location of the vented dryer will result in longer drying times.

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V. REPAIRS

1. Troubleshooting

When implementing troubleshooting procedures, please comply with the following:

•All test programmes should be run.

•If “Test component” is indicated in the Procedures column of the troubleshooting

table the components are to be tested in accordance with their electrical specification.

To test the component, remove the plug from the power module.

•Check that the plug-and-socket connections are properly attached.

•If electronic modules are replaced, note down the result of the test programs on the

appropriate label.

•When handling electronic modules, comply with the EGB handling regulations.

•Put the replaced electronic modules back into the original packaging.

Error

no. Error display Possible cause Test / Procedure

1“Drying” LED flashes

in the progress

indicator = NTC fault

(NTC R4)

Appliance ambient

temperature < 0 °C. Customer instruction:

Do not operate the

appliance below 0 °C.

NTC R4, cable or plug-and-

socket connection defective. Remove the cable from the

power module. Test NTC,

cable and plug-and-socket

connection.

Power module defective. If 1 A and 1 B are o.k., start

“BW cupboard dry” test

program. If LED in the

progress indicator displays

NTC fault, replace the

power module.

2“Iron dry” LED

flashes in the

progress indicator =

NTC fault (NTC R2)

NTC R3, cable or plug-and-

socket connection defective. See Error number 1.

3“Cupboard dry” LED

flashes in the

progress indicator =

NTC fault (NTC R2)

NTC R2, cable or plug-and-

socket connection defective. See Error number 1.

4 “Extra dry” LED

flashes in the

progress indicator =

overheating

Fluff filter blocked. Clean the fluff filter.

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Error

no. Test / ProcedurePossible causeError display

Re 4 B

Air-intake / exhaust-air

passages blocked. Test air passages.

Overload Customer instruction:

Load < 5 kg dry weight.

Fan impeller loose. Test fan impeller.

Motor is not rotating. See Error number 7.

Heater does not switch off. See Error display 8 B/C.

5“End” LED flashes

(display only in test

program!) = time

error

– “Washing not

drying properly”

– “Drying time

too long”

– “Dry in 180 /

240 minutes”

Washing too wet,

initial moisture too high. Customer instruction.

Overload, < 5 kg dry weight. Customer instruction.

Fluff filter blocked. Clean fluff filter.

Thermal cut-out B9 has

tripped. See Error number 14.

Short-circuit or shunt circuit

in conductivity system. See Error number 12 B.

Heater defective. See Error number 8.

Motor is not rotating. See Error number 7.

Mains voltage too low. Measure mains voltage

under load.

Required voltage 230 V

(+10 % / –15 %).

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Error

no. Test / ProcedurePossible causeError display

6Drum is not rotating. A

Motor is not rotating See Error number 7.

Belt loose, slipping or

defective.

Clamping device defective.

Test belt and clamping

device.

Drum blocked or

overloaded. Test drum.

7Motor is not rotating

– rotates only in one

direction,

– rotates constantly.

Motor, cable or plug-and-

socket connection defective.

Motor protector has been

actuated.

Motor capacitor defective.

Test motor, capacitor and

wiring.

Door switch defective. See Error number 15.

Power module defective. Start “BW cupboard dry”

test program and measure

drive voltage for motor.

Clockwise rotation:

Mains voltage between

X11–10.5 and X11–10.3;

Anti-clockwise rotation:

Mains voltage between

X11–10.5 and X11–10.4

Before performing this test,

remove the heater plug, as

thermal cut-out B9 will trip

immediately without the

motor.

8Is not heating. A

Thermal cut-out B9 has

tripped. See Error number 13 B.

Heater defective. Test heater and cable.

NTCs defective. Test NTCs (cold resistance)

and wiring.

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Error

no. Test / ProcedurePossible causeError display

Re 8 D

Power module defective. Start “BW cupboard dry”

test program.

On the power module

measure the drive voltage

(mains voltage) for heater

E1, 2, 3.

Excessive contact

resistance in sliding contact

system.

See Error number 11 E.

9Heater continuously

on.

(Dryer not started.)

Heater defective. Test heater and cable.

Power module defective. See Error number 8 C.

10 – Washing not drying

properly,

– Too damp.

Wrong programme selected. Customer information:

Select higher degree of

dryness.

Door switch or power

module defective. See Error numbers 15 A

and 15 B.

Excessive contact

resistance in conductivity

system.

Start “Gentle dry” test

program. Short-circuit

between the agitator and

drum.

If an error is displayed:

Test sliding contact system

and internal contact

between agitators for

continuity.

Max. 1 kΩbetween agitator

and Pin 3 on the plug.

Max. 1 kΩbetween drum

and Pin 1 on the plug.

If resistance is o.k.:

Repeat test program, with

jumper between plug-and-

socket connection X11-15.1

and X11-15.3. If there is no

error display, do not replace

the power module.

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