57ecoTEC plus 937 installation and maintenance manual
Code Meaning Cause
F.71 Flow NTC reports constant value Flow NTC is defective
F.72 Flow and/or return NTC fault Feed and/or return NTC is faulty (tolerance too great)
F.73 Signal water pressure sensor in the wrong range (too low) Line to water pressure sensor is interrupted or has a short-
circuit to 0 V or water pressure sensor faulty
F.74 Signal water pressure sensor in the wrong range (too
high)
Harness to water pressure sensor has a short-circuit at
5 V / 24 V or internal fault in water pressure sensor
F.75 No sudden change in pressure was detected on turning on
the pump
Water pressure sensor and/or pump faulty (pump seized - check
system water for contamination)
Air in heating system, automatic air vent system faulty
Too little water in the unit; check adjustable bypass;
Connect expansion vessel in return;
F.76 Overheating protection on primary heat-exchanger
activated
Cable or cable connection of fuse in the primary heat exchanger
defective, replace primary heat exchanger
F.77 Condensate pump or return signal from accessory module
blocks heating
Condensate pump faulty or return signal from the exhaust gas
flap has activated
F.78 Incorrect configuration of accessories Control Center VR 65 connected to combination boiler
F.90 Communication with shift load storage tank module
interrupted
Check wiring harness from combi boiler to shift load storage
tank (PE Bus). If combi boiler is to be operated without shift load
storage tank, set d.92 = 0
F.91 Sensor error on shift load storage tank module (NTC)
con No communication with the printed circuit board Communication fault between the display and the printed circuit
board in the electronics box
Table 8.4 Error codes (continuation)
8.2 Test programmes
Special functions can be triggered in the appliance by
activating various test programs.
These programmes are listed in detail in Table 8.5.
• The test programmes P.0 to P.6 will be started when "
Power ON“ is turned on and the "+“ button is pressed
for 5 seconds simultaneously.
The display shows "P.0 “.
• Press the "+" key to start counting the test
programme number upwards.
• Press the "i“ to operate the appliance now and to start
the test programme.
• To de-activate the setting mode, simultaneously push
the buttons "i“ and "+“. You can also end the test
programmes by not pushing any button for a 15
minute period.
Display Meaning
P.0 Bleeding test program The heating circuit and the hot
water circuit (only on combination boilers) are bled
via the automatic air vent (the cap of the automatic
air vent must be released two turns).
P.1 Test programme where the appliance is operated in
full load after successful ignition.
P.2 Test program where the appliance is operated with
minimum gas volume (ignition gas volume) after
successful ignition
P.3 not available
P.4 not available
Table 8.5 Test programmes
Display Meaning
P.5 Test programme for checking the safety temperature
limitation: The unit is heated by avoidance of the
regular switch-off by the feed regulator until a
temperature of 97 °C is reached.
P.6 Filling programme: The diverter valve moves to the
centre position.
Table 8.5 Test programmes (continuation)
8.3 Resetting the parameters to factory settings
Besides the option to reset individual parameters
manually to the factory settings specified in Tables 9.2
and 9.3, you can also reset all parameters
simultaneously.
• In the second diagnostic level, under the diagnostic
point "d.96" change the value to 1 (see Section 8.1.2).
The parameters of all adjustable diagnosis points now
correspond to the factory settings.
Troubleshooting 8
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