F10 on the CDT80 refers to the heater and one shot cut out. If you have a multi meter check for continuity on the J4 terminal block on the module, between the Orange and Brown wires terminals 4 and 3. The orange wire runs through the one shot cut out and the cycling stat to the top heater while the Brown wire is the return from the lower heater. you may need a new heater or control board.
casper....www.selfix-uk.co.uk, October 2008
