Webasto Thermo Top Pro 120 Workshop Manual page 20

6 | Malfunctions and troubleshooting
*: Indicator lamp of control element flashing:
count the number of long flash pulses after 5 short flash pulses.
Analogue Fault code
fault code (hexa-
decimal)
F20 H25
or HA5
20*
* The number of long pulses corresponds to the number of the fault code.
6.6.2 Troubleshooting without error code output
NOTE
We generally recommend the following procedure:
u Check fuses
u Check operating voltage
u Check for damage and ensure passages are clear:
–– combustion air intake
–– exhaust pipe
–– fuel line
u Also check condition of filter.
Symptom
Heater does not respond, no
component running. Indicator
lamp not flashing.
20 / 49
Fault message / Possible causes
Symptom
Exhaust gas temperat-
ure sensor defective
Heater fouled
No fuel preheating Heater cartridge wiring
defective
Heater cartridge defect-
ive
Possible cause
Operating voltage
Indicator lamp (control ele-
ment, Quick Heating button)
Recommended action in workshop
2. Check exhaust gas temperature sensor, replace if
necessary
3. Visual inspection with cleaning of inner surface of
heat exchanger and combustion tube, replace if ne-
cessary
1. Check wiring and connector for damage, break
and short-circuit
2. Check operation of heater cartridge, replace if
necessary
Possible troubleshooting
1. Fuse blown
u Rectify cause, change fuse
2. Unlock heater
3. Supply voltage to heater con-
nector
u Measure voltage
1. Control element fuse blown
u
Rectify cause, change fuse
2. Supply voltage on control
element (switch with function
display)
u
Measure voltage at pin
3. Continuity at control element
(switch with function display)
u
Check pin to ground
4. Control element indicator
lamp defective
u Replace control element if
necessary
9039412C Workshop manual TTP 120 _ 150
Comments / Service
The indicator lamp is provided
by the heater (see wiring dia-
gram). Check / replace control
element.