0409 - Troubleshooting information Models 124, 126, 201 with auxiliary heating BBW/DBW 46

83-409

Troubleshooting information

Complaint

Possible cause/remedy

Auxiliary heater does not operate.

Perform function test (83-410).

Immediately after switching on heater, the

1. Fuse of glow plug faulty.

combustion air blower starts for approx. 60 s. Then,

2. Glow plug not operating

the heating switches to fault; the green operating

(test glow operation 83-440).

lamp goes out.
Models as of 08/86 with control unit 105.499
(Webasto number).

Approx. 30-35 s after switching on heater, fuel

1. Test exhaust emission level (83-475).

metering pump and combustion air blower start,

2. Test glow operation (83-440).

combustion is always achieved during repeat start
only.

Auxiliary heater (gasoline models only) slaps when Ceramic matting disc damaged by hole of
starting, does not start or starts only after switching approx. 4 mm dia. at fuel inlet.
on

Replace ceramic matting (rep. kit) (83-471).

several times.

Auxiliary heater does not start even after automatic Vapor lock in fuel line
repeat start. This fault relates primarily to models

1. Check delivery of fuel metering pump

124 and 126 with catalytic converter.

(83-480).

2. Install new fuel lines with wire core,
production breakpoint approx. 03/88.

Auxiliary heater operates properly but switches off 1. Charge battery and test.
when operating and the green operating indicator

2. Perform function test (83-410).

lamp
goes out.

Auxiliary heater does not move into part-load

1. Resistor on heater not operating.

operation

Check resistor for combustion air

at coolant temperatures above 80°C in heater.

blower(83-465).

Combustion stops after full-load operation. The fuel
metering pump continues to operate at approx. half

2. Control unit faulty.

the number of cycles (clicking can be heard approx.
1
to 2 times per second). Dark smoke from heater
and
heater switches to fault.

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On models 124 and 126.03/04 up to approx. 06/85, Induction voltages from auxiliary heater
the heater switches off or moves into combustion

mono valve.

interval without after-running.

Install new mono valve with production

number 554 or higher. The production

number is stamped in green on top of the

mono valve.

Fuel metering pump noisy when operating.

Audible operating noises are a standard
production feature. If operating noise is
extremely loud, contact VKT/MG.

No or only occasional preglow on heaters with

1. Coaxial connector has loose contact or

coaxial

interruption. Replace connector.

connector for glow plug.

2. Test glow operation (83-440).

Fuse (16A) faulty, glow plug not operating.

1. Glow plug has short-circuit; replace
glow plug (83-441). If glow plug
removed has carbon deposits, also
replace ceramic matting (83-471).

2. Cage of ceramic matting has been
damaged when fitting, with the result
that it is touching the coil of the glow
plug; replace cage together with
ceramic matting (83-471).

Heater moves into control mode or part load, e.g.

Moisture has got into the 12-pole connector

after

on the heater. Clean and dry housing of the

engine wash, although temperature switching

connector. When fitting, pay attention to

points of

correct pin assignment of connector.

80°C and 85°C are not reached.

Auxiliary heater cannot be switched off.

Voltage is not interrupted by timer.
Test timer (83-415).

Temperature fuse has melted. This cuts off the

1. Air in coolant circuit, rectify leak and

voltage supply to the fuel metering pump.

bleed coolant circuit.

2. No coolant circulation because of:
a) kinked or crimped coolant hoses;

b) circulating pump not operating.

Test circulating pump (83-460).

3. Temperature sensor faulty.

Test temperature sensor (83-445).

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Auxiliary heater operates properly, but switches to  Circulating pump not running.
combustion interval within approx. 10 min. (coolant  Test circulating pump (83-460).
gauge of instrument cluster below 50°C). Only cold  Model 201
air

Switchover valve not operating, heater tap

comes out of the air vents.

is not opened.

Test circulating pump (83-495).

Auxiliary heater operates properly but only cold air Model 124, 126
comes out of the air vents.

1. Temperature selector set to MIN or too
low a temperature.

2. Auxiliary heater mono valve relay does
not switch over; the mono or dual valve
for the heat exchanger is not open.
Model 201

Heater switches are not set to "heat".

Auxiliary heater and heater blower operate properly 1. Main air vent closed.
but no air comes out of the air vents. Models 124,

a) Blower switch is not set to position

126 with automatic heater control or automatic

temperature control and model 201.

b) Main air vent is not operated by

blower switch.

Heater blower does not operate when coolant

Check whether heater blower operates

temperature in heater is above 60°C.

when ignition is switched on.

1. Heater blower does not operate:
test voltage supply.

2. Heater blower operates:

a) Test cable of connector A at control

unit from pin assignment 1 to 3

(wiring diagram 83-405).

b) Test temperature sensor (83-445).
c) Control unit faulty.

Intermittent operating noise from operating

Subsequent installation of additional relay

circulation

to prevent circulation pump noise (83-462).

pump on idle/driving mode when auxiliary heater
switched off, model 124.0 up to approx. 09/92
(excluding 124.034/036),
models 124.120/128/133/188/193/3 up to approx.

01/93,

models 124.125/127/130/180/185/2

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Soot or smoke from auxiliary heater despite

Poor combustion:

exhaust gas being correctly set.

1. Test fuel delivery (83-480). If correct,
replace combustion air blower and reset
exhaust gas (83-456 and 83-475).

2. On diesel models, before renewing
combustion air blower, first of all check
whether ground cable is fitted to pin
assignment 6 of 8-pole plug connector
on control unit.

Smoke from auxiliary heater when engine running. Pressure reducer not operating.
Diesel models with vehicle ident. end no.

Test pressure reducer (83-487).

124-A 667677/F 032883 up to B 054061/F 121270

and

201-A 432785/F 415111 up to A 459586/F 569589

only

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