64
Installation and maintenance instructions ecoTEC plus 937 0020031552_06
Code
Meaning
Cause
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.80
Interruption or short-circuit of SWT inlet sensor only in
conjunction with F.91
NTC defective, NTC cable defective, defective plug connection at
NTC, defective plug connection at APC electronics
Plug at sensor has short-circuited to housing, short-circuit in
cable harness, sensor defective
F.81
APC loadpump fault connected to F.91
Inadequate heat transfer between the heater and storage tank.
– Check storage tank charge sensor and storage tank sensor
– Air in the APC pump
– Check pump wiring harness
– Secondary heat exchanger blocked
– Priority changeover valve defective
– Pump defective
– Plate-type heat exchanger scaled
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)
NTC faulty, NTC cable faulty, faulty plug connection on NTC,
faulty plug connection on the electronics
con
No communication with the printed circuit board
Communication fault between the display and the printed circuit
board in the electronics box
Table 9.4 Error codes (continued)
9 Troubleshooting
Summary of Contents for ecoTEC plus 937
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