User's Manual

5TROUBLESHOOTING T HERMO 90 / 90 S
5-2
5.3 Failure Symptoms after Switch-off
upon Failure
NOTE:
When operated with a switch the type of failure is
indicated by a flash code of the operation indicator light
during heater run-down.
After five short signals the long flash pulses are counted.
The heater Thermo 90 S, with standard timer, outputs
errors to the timer display for indication (see 3.6.3).
The following table may also be used as representative
reference.
Failure Symptom Probable Cause Remedy
No function Electrical wiring, fuses Check fuses
Check battery connections
+ at A5 / – at A3 / + from A1
(Thermo 90)
+ at 12 / – at 9 / + at 3, connector X12
(Thermo 90 S)
Control unit defective Replace control unit
1 Flash pulse (F 01) Fuel system Check fuel level
(no start) Check fuel filter
Bleed fuel system
Combustion air/exhaust duct Check combustion air/exhaust duct for
foreign matter and clean as required
Burner Clean burner or replace as necessary
2 Flash pulses (F 02) Fuel supply Check fuel level
(flame-out during operation) Check fuel filter
Bleed fuel system
Burner Clean burner or replace as necessary
3 Flash pulses (F 03) Electrical power supply Check battery (load test)
(low voltage) Check electrical connections
4 Flashes (F 04) Flame sensor defective Replace flame sensor
(flame sensor
continuously hot)
5 Flash pulses (F 05) Wiring Check wiring for damage, open
(flame sensor) connections or short circuit
Flame sensor defective Replace flame sensor
6 Flash pulses (F 06) Wiring Check wiring for damage, open
(temperature sensor) connections or short circuit
Temperature sensor defective Replace temperature sensor
7 Flash pulses (F 07) Wiring Check wiring for damage, open
(fuel metering pump) connections or short circuit
Fuel metering pump defective Replace fuel metering pump
(temperature limiter) Coolant circuit (Thermo 90 only) Check coolant level
Bleed coolant circuit
Reset temperature limiter
Fig. 5-2 Failure Symptoms after Switch-off upon Failure (Part 1 of 2)