My pressure switch has 3 wires so has only one level. I have tried tapping it, while trying to run the pump/spin cycle, with no success.
I'm pretty sure that when the spin fails to occur, the pump is running continuously with no water in the machine, so think it must be a problem of the switch, or the electronics. Might be worth trying a new swich, but haven't seen any for sale.
Otherwise, I'm beginning to think I may just have to get a new machine. As you say, it's getting a bit old...
Would be glad of any more suggestions, but in any case thanks for all your helpful advice. I've learned a lot about washing machines and how to investigate their troubles!