Hotpoint WD860 Ultima F13
I have the UK Whitegoods Fault code guide, but the only reference is on page 26 which says high dryer temperature, dryer motor ok, dryer NTC ok, the heater rattles (makes a noisy when the machine was spinning) but is ok.
Also on p26 “All seem to use the EVO2 software” then on p30 “EVO2 software fault finding” there is no reference to F13
Have you stripped the heater box down, the fan often comes adrift and drops down slightly, fouling on the heater box when hot. Usually trips the one shot though.