We are seeing four thermal switches.



The black one with BLUE wires is the temperature limit switch on the NEUTAL line. It appears to be connected to the metal chassis.

The beige one with BROWN wires is on the LINE input feeding a heater. You said that this measures as OL.
Putting a jumper across the BROWN wires did not fix the problem?

Set your DMM to highest voltage AC (700 VAC).
Connect one lead of the DMM to the metal chassis.
Connect the other lead of the DMM to each of the BROWN wires, one at a time.

 

The black one with BLUE wires is the temperature limit switch on the NEUTAL line. It appears to be connected to the metal chassis.

As always, thanks MrChips. The blue doesn't touch the metal chassis. It feeds from the heater elements which are suspected in the structure by a kind of fire-proof type 'cardboard'. There are no wires attached to the metal chassis, which ultimately I expect is earthed to the assembled machine's structure when reassabled. I did already test connecting the two brown wires (bypassing the beige OL). It tricked the control panel into thinking the filter was blocked and refused to start a cycle at all. With this new information, would test would you suggest?

 

I cannot see clearly where the BLUE wires are connected. As I said, the BLUE wires appear to be on the NEUTRAL side of AC. Also it would be nice to know where the BROWN wires go.

Don't use the words "tricked the control panel". This leads to confusion.
How did you jumper the BROWN wires? Was it a solid connection?
What happens when the BROWN wires are connected and then not connected?
How does the controller knows that the filter is blocked?

Use the BLUE wires for connection to AC NEUTRAL.
I am assuming that the BROWN wires feed AC LINE.
In which case you should read 240 VAC across BLUE and BROWN wires.

 

Thanks MrChips. Due to inexperience, 3 kids and mounting laundry, I've got a friend who wants to take this project (and all parts) on for himself whilst we get a new machine. I'll show him all your advice so he takes it forward. At least he's good at soldering. I've also learnt a lot about how these boards work from you and others here and can't thank you enough! Your advice helps me carefully choose another machine too (parts easy to access, find secondhand in 10 years, parts easy to get, etc). Not so much defeated, just logistics got me in the end.