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Instruction manual GWV 79
Code + description Cause Measures to take Comment
F03 (lock out error)
The pressure switch
fails to work correctly
Damaged wiring/Open
circuit
1. Check the wiring between the pressure switch and the
controller
2. If necessary, replace the wiring
If the error cannot be resolved or is persistent, contact your
installation engineer
To replace the necessary parts, you must contact your installation
engineer
Pressure switch not
closing
1. Check the running speed of the fan (12.5 "Displaying the
appliance selection")
2. Check that the hoses are fitted correctly to the pressure switch
and the ventilator's air supply hose. Refit them if necessary
3. Check for cracks in the hoses on the pressure switch and in the
air supply hose for the fan. If necessary, replace the hoses.
4. Check that the flue gas outlet is compliant (3.9 "Air supply and
flue").
5. Measure the pressure differential across the pressure switch.
See the table(2.4.5 "Pressure switch"). If there is insufficient
pressure difference, clean the heat exchanger. If the pressure
differential is acceptable, check that the pressure switch is
closing, using a multimeter.