hi navtec.
here are the operation code( ie alarm led is off and the 8 led segment displaying the code is on ( not flashing) all the time for my THR 5-25 M75. HOPE IS THE SAME FOR YOUR BOILER.
0--awaiting demand for dhw or heating
1--shunt6 not present switch open
2&3--fan speed rise...
hello every body I been a Geminox THX5-25M75 owner since 90ish when a the company in hayes london when burst and brought this model for around £600 was a good value at the time .
Having got a degree in electronics I did my research and it came down to the conclution that it was this model...