5 Faults, Troubleshooting Thermo Pro 90
509
16 Exhaust gas tem-
perature too
high
Exhaust temperature sensor
defective
Check wiring for damage, open circuit and short circuit
Functional check of exhaust temperature sensor; replace
exhaust temperature sensor if necessary
Heater sooted Visual inspection with cleaning or replacement of burner
unit, burner head and inner surface of heat exchanger
17 Exhaust temper-
ature sensor
defective
Wiring Check wiring for damage, open circuit and short circuit
Exhaust temperature sensor
defective
Functional check of exhaust temperature sensor; replace
exhaust temperature sensor if necessary
Error code
number/
Number of
flashing
pulses
Fault message Possible causes Recommended workshop action
Fig. 503 Error code output by standard timer/switch
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