5 Troubleshooting Thermo 90 S / Thermo 90 ST
504
5.4.2 Back wall with metal evaporator
• The pilot flame outlet opening (Fig. 504) must be clear
otherwise no start will occur.
Remedy
Replace burner
• Cracks, flaking as well as black or other discoloration
of the evaporator do not lead to burner failure and are
not significant.
• Coke deposits on the evaporator surface (except for
the pilot flame outlet opening) are normal; as a rule,
the burner cleans itself due to the load changes from
full load to part load and part load to full load.
Fig. 504 Visual check, pilot flame outlet opening
5.4.3 Combustion chamber
• The combustion chamber (Fig. 505) should not be
damaged (e.g. dented). A dented combustion
chamber can lead to poor combustion or carbon build-
up in the heater.
Remedy
Replace burner
• The air holes (Fig. 505) in the combustion chamber
must not be blocked up by carbon deposits. If the air
holes are blocked up by carbon deposits, this may
result in failure of combustion to start or to run
effectively.
Remedy
Carefully scratch clear the air holes
5.4.4 Complete burner
• The cables of the glow plug and flame monitor must
be routed as shown in Fig. 503.
• The screw connection of the housing and combustion
chamber (Fig. 505) must be tight.
• The housing and the combustion chamber (Fig. 505)
must be firmly connected together and there must not
be any play (check by moving the fuel pipe slightly).
• The round sealing ring (Fig. 503) must evenly
surround the fuel pipe and must not leak.
• The distance (gap) between the edge of the housing
and the top edge of the combustion chamber
(Fig. 505) does not have to be even all the way
around.
• The insulation (Fig. 503) must not be missing.
Fig. 505 Visual check, complete burner
Pilot flame outlet opening
Metal evaporator, petrol
Pilot flame outlet opening
Metal evaporator, diesel
Combustion chamber
Swirl orifice
Air holes
Gap between housing
and combustion chamber
