glow worm ultracom 2 24 cxi heating not getting up to temperature

[dougiex]

Hi, having a problem with the above boiler. Cannot adjust the heating temperature. When i switch on at first it shows 21 deg and when i use the + button to adjust up it shows "no". I have a fault code which is F 00 which is the heating flow thermistor, or wiring. I removed the thermistor (which I believe is the front one of the two) and it read 8Kohms at room temp and when I put in hot water the resistance was changing. I called glow worm to try and get technical assistance and queried the 8Kohms which they said was acceptable for the thermistor, but they said that the "no" on display was that my boiler was being controlled externally. I have the Climapro 2 controller which was on top of the kitchen cupboard and has not been touched since the boiler was installed approx 7 years ago and it is actually completely dead even after installing new batteries so don't see how this could affect anything. Also when i switch on the heating the pump runs constantly. Anyway, not sure if the external controller thing is a red herring or not. Would appreciate any help, thanks in advance.

 

[dougiex]

Further to above, occasionally the burner fires up and shows approx 48 deg then shuts off and display returns to 23 deg. Checked both thermistors via the socket at the board and both showing 10Kohms. Have tried resetting boiler to no avail. If I can remove the interface/bus connections for the Climapro I would do so but not sure how to do.