83-410

Function test

Commercially available tool

Thermometer

-20°C to +70°C

Note
Perform function test at approx. 20°C (room

temperature) and with engine cold.

Preparations for function test
1

Attach exhaust extractor to tailpipe of

exhaust silencer.

2

On model 124.0 up to approx. 09/92

(excluding models 124.034/036) detach 2-pin
plug connection X73 in engine compartment,
except for model 124.020 with automatic
heater control. On model 124.020 with
automatic heater control, detach relay K15
(2-pin connector X73 is not fitted)

3

On models 124.1/2/3 detach 2-pin plug

connection X73 in engine compartment,
(excluding models

Arrangement

124.120/128/133/188/193/3 as of approx.
02/93 and models 124.126/129/131/186/191)

X73

Plug connection - circulation pump relay

(excluding model 124.020 with automatic

(2-pin connector X73 is not fitted).

heater control and models
124.019/022/028/032/034/036/042/052/
066/079/082/088/092)

Arrangement model 124.036

X73

Connector - circulating pump relay

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Note
The relays with connectors may be arranged
as desired in the relay holder. If relay K15 is
disconnected, the circulation pump no longer
operates with the ignition switched on and
the temperature selectors set to "MAX".

4

Switch on ignition. There must not be any

coolant temperature reading on the
instrument cluster.
5

Switch off ignition.

6

Close left and right side vents and also

center vents.

7

On vehicles without automatic climate

control:
turn airflow switches to the arrow pointing
upwards.
Turn left and right heater switches or
temperature selectors to "MAX".

Heater

switches on model 201

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8

On models with automatic climate control:

press pushbutton (arrow) "DEF" and turn

temperature selector (arrow) to "MAX".

9

Insert thermometer into left-hand

defroster vent.

Function test

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Switch on auxiliary heater with the instant
heat button.

Green operating indicator lamp of timer
comes on.

Yes

No

1

Fuse (8A) faulty

(see wiring diagrams in Electric

Wiring Diagrams file).

2

Test timer (83-415).

Glow plug pre-glows, air around glow plug is
heated.

Yes

No

Test glow operation (83-440).
Note

On models as of approx. 08/86 with

control unit 105.499 (Webasto

number) the combustion air blower

starts up immediately for approx. 60 s

if the glow operation is faulty before

the heater switches to fault.

After approx. 35 s the combustion air blower
can be heard to start.

Yes

No

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Check whether green operating
indicator lamp of timer is off.

Yes

No

Replace flame monitor
(83-436).

Test combustion air blower (83-455).

Combustion commences, exhaust pipe
becomes hot.

Yes

No

Wait for repeat start, repeat start
follows.

Yes

No

1

Check state of charge of

battery.
2

Check glow operation

(83-440).

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Combustion commences, heater
running.

Yes

No

1

Check temperature cut

out (83-450).

2

Check fuel metering

pump (83-480).

3

Check flame monitor

(83-435).

4

Check state of charge of

battery.

The heater blower starts up automatically
approx. 6 min after commencement of
combustion.

Yes

No

See troubleshooting information
(83-409).

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The air outlet temperature must be at 45°C
approx. 2. min after the heater blower
switches on.

Yes

No

Refer to troubleshooting information
(83-409).

Switch off auxiliary heater by pressing the
instant heat button.

End of test
After completing the repairs on model 124,

reinstall 2-pole connector X73 or relay K15.

Note

The controlled mode has not been tested.

Refer to troubleshooting information (83-409)

for complaints.

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