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
t h e v olum e – h old d ow n t h e b utton , t h 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 in
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
is 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
a 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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If 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.
ϑ
Min.
Max.
Limit
Heat
setting
3 or 2
0
If the temperature limit is exceeded, all heaters are switched of f. The heater is not switched
on again until the temperature has dropped to υ 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)
A
Appliance ambient
temperature < 0 °C. Customer instruction:
Do not operate the
appliance below 0 °C.
B
NTC R4, cable or plug-and-
socket connection defective. Remove the cable from the
power module. Test NTC,
cable and plug-and-socket
connection.
C
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
A
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.
C
Overload Customer instruction: Load < 5 kg dry weight.
D
Fan impeller loose. Test fan impeller.
E
Motor is not rotating. See Error number 7.
F
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”
A
Washing too wet,
initial moisture too high. Customer instruction.
B
Overload, < 5 kg dry weight. Customer instruction.
C
Fluff filter blocked. Clean fluff filter.
D
Thermal cut-out B9 has
tripped. See Error number 14.
E
Short-circuit or shunt circuit
in conductivity system. See Error number 12 B.
F
Heater defective. See Error number 8.
G
Motor is not rotating. See Error number 7.
H
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.
B
Belt loose, slipping or
defective.
Clamping device defective.
Test belt and clamping
device.
C
Drum blocked or
overloaded. Test drum.
7Motor is not rotating
– rotates only in one
direction,
– rotates constantly.
A
Motor, cable or plug-and-
socket connection defective.
Motor protector has been
actuated.
Motor capacitor defective.
Test motor, capacitor and
wiring.
B
Door switch defective. See Error number 15.
C
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.
B
Heater defective. Test heater and cable.
C
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.
E
Excessive contact
resistance in sliding contact
system.
See Error number 11 E.
9Heater continuously
on.
(Dryer not started.)
A
Heater defective. Test heater and cable.
B
Power module defective. See Error number 8 C.
10 – Washing not drying
properly,
– Too damp.
A
Wrong programme selected. Customer information:
Select higher degree of
dryness.
B
Door switch or power
module defective. See Error numbers 15 A
and 15 B.
C
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.