Report "Hi all, I have a brivis buffalo 85 central heating unit. Currently the unit runs fine but intermittently the fan will run on for 10 seconds or so then off again. A couple of times the fan has run overnight regardless of the controller being switched on or fan auto manual etc. I have replaced the old controller with a compatible honeywell one a year back so that's not the issue. Any ideas on what the problem could be would be great help. I suspect the fan thermostat for the exchange is faulty. Thanks"