From another site...
I have a Microgenus HE 32 MFFI boiler which keeps cutting out with error code A77.
The manual says this is due to either:
- Condensate trap full of water
- Condensate sensor short circuited
- Condensate sensor in open circuit
But you do not say your boiler so this may be of no use to you.
Peccavi
January 2013