Webasto Thermo 350 Service Manual download pdf (Page 30)

5 Troubleshooting Thermo 230 / 231 / 300 / 301 / 350

504

5.3.2 Fault Symptoms

5.3.2.1 Fault Symptom "No Start"

NOTE

Heaters with control unit 1572D:

If the heater performs 8 consecutive attempts to start due

to a malfunction, the heater enters an error lockout and

stops any further attempts to start. This error lockout is

superior to the normal error lockout condition.

The error lockout reset is achieved by switching the heater

on and disconnection of the heater power supply during

run-down.

Switch on heater.

Is combustion air fan

operating?

Motor and fan wheel

free to move?

Is fan wheel caught

in cap?

Is voltage present on

plug contact A3?

Check fuses F1/F2/F3

and relais K1, K2 and

replace as required

(control unit 1572

only).

Does trouble persist?

Check motor electrics

and replace as

required.

Replace cap

and fan wheel.

Is voltage too low?

Rated value >20,5 volts

(± 0,5 volts)

Check electrical

wiring and

connections.

Does trouble persist?

Low voltage switch

off during start-up.

Check battery.

Control unit defective,

replace.

Is fuel free of bubbles

in supply and return?

Is fuel filter

contaminated?

Fuel suction line

leak?

Fuel lines empty? Are O-rings in fuel

pump?

Is pump mounted

securely?

Replace fuel filter. Retighten line

connections,

replace lines as

required.

Repeat start (several

times if necessary)

until lines are filled.

Fuel pump defective,

replace.

Is solenoid valve

connected to

electrics?

Connect solenoid

valve.

Is gap between igniter

electrodes ok?

Check gap between

igniter electrodes.

Is nozzle free of foreign

matter and deposits

and properly secured?

Replace nozzle.

YES

Is viewing glass of

flame sensor

contaminated?

Clean window and

viewing glass.

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Webasto Thermo 350 Service Manual Page 30

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