i have a glow worm boiler model 18sxi its comming up with a error message f5 its keeps flashing when the heater is turned on.. can some one help

singhd06, October 2008

I have also read it can be a blocked waste pipe as they often overflow into the waste pipe of the kitchen sink.

Paul, January 2009

I have the same boiler and same fault, it works for around 3 days and then goes again. I too have been using the red button to bring the system back online. I spent a while bleading the radiators the first time to make sure there wasnt air in the system as this can apparently cause F5.

I am wondering if there is a way of bleading any air from within the boiler itself?

When mine does go wrong, usually in the morning at 6am it make a loud clatering noise and the temperature starts to decrease rapidly.

Paul, January 2009

I have a similar problem. F5 means there is an overheat problem with the system. This could be a few things, but usually it is the overheat thermostat going faulty. I had mine replaced today, and the problem persists.

To mend the problem temporarily remove the outer (two screws on bottom) and inner (another two screws on the front) covers and locate the overheat thermostat on the top left. If it connected to one of the pipes and has two wires coming out of it. Turn the unit off on the front, press the little red button on this thermostat in, turn the heat down a little, and turn it back on.

It will work for a while, but there is still something wrong. I have checked the usual suspects like system pressure (needs to be more than 1 bar and less than 3, (1.5 optimal) and air out of the system.

Let me know if you have resolved this issue.

lspnr, December 2008