hot water not working brittony combi 80?

You do give any detail.A common fault is blockage in the DHW heat exchanger.When this occurs the boiler will fire up on water demand but go out shortly after and the water runs cold.
The boiler will only fire up againwhen you switch the water off and back on. Taking out the heat exchanger is quite easy.Give it a good decoke with descaler and flush it through with a hose.
You might be surprised how much gunk comes out.This boiler is identical (well almost) to the Baxi genesis 80/90 which have good srvicing instructions on the web.

Martyn
November 2007