Hi, I just wanted to share that the reed switch replacement solved my F13 error as well. Machine is about 7/8 years old and the fault was intemittant. I removed the circuit board and tested the continuity and my multi meter showed that the reed switch was stuck in the closed state when it should have been open.
I replaced it with: SP-NO Reed Switch, 1A 230V ac/dc Stock no.:362-2530 since I suspect that sensor does actally carry 240v (based on my inadvertent contact with the board while it was live… be careful). The replacement is a little bigger but still fits comfortably between the two soldering points and is super simple to replace, I was just careful to ensure that the reeds in the switch faced up/down rather than side/side.
Thanks Dave!