The error code F35 is commonly associated with the Sud error, which comes on within a minute of running any cycle. It means the Analog Pressure Sensor may have gone bad. t could also mean the Air Pressure Tube from the Sensor has a hole or isn't connected. I would also make sure I was using HE detergent as the regular stuff will set this off.
Once you get the new Sensor, remove the 3 screws holding the top panel inplace - they are on the backside on the very top. Remove the top and look at the far back upper right corner (looking from the front). There is a small crimson & black piece attached to the metal side wall with 5 blue wires & 1 black wire (pressure tube) attached to it. Make sure there are no leaks or disconnects...i
Takes less than 15 minutes to fix, the most time consuming part is taking the old part out, just turn it counter clockwise and pull.
I too was vexed by the notorious f35 ghost. I followed your advice and noted that the blue wires joined a "river" of wires running to a switchboard located on the right side/front (if you are looking down and facing the front of the washertop). I followed the blue wires and found that the wires ended in an electronic plug which had come loose. I snapped it in place, and ...voila! No more f35.
So I second the notion of checking this connection before deciding your switch is bad.
Your answer led me to my answer so thank you!