when I switch on green led appears, boiler will not ignite after a period of time red led will come on. If you remove the air cover box or slightly hold out at one of the bottom corners after remove of clip ! its all systems go. after securing the air cover box the boiler will operate normal; until you turn on your hot water along with central heating system boiler then will go into shut-down. On previous occasions when appliance has acted as above I have slip of the two rubber tubes that are connected to the air pressure switch which has resulted in appliance operating normal for both central heating and hot water

Jim, January 2011