AL01 - Anti flood switch operated
AL02 - Valve or connections
AL03 - Time out - drain
AL04 - Thermistor (module)
AL05 - Circulation pump
AL06 - Time out - fill
AL07 - Not used
AL08 - Time out - heat
AL09 - Software recogntion error
AL10 - Heating circuit
AL99 - Communications error - connectors, cables etc.
H20 - Time out - fill (taps)
Fergie, November 2010