I Paid £55 for a BROKEN £899 Delonghi Eletta Coffee Machine - Can I FIX it?

The £55 De'Longhi Eletta coffee machine was successfully restored to working condition for approximately £120 by addressing a faulty thermal heating circuit and resolving severe internal water leaks.

• Failed thermal fuse — Tested the boiler's thermal cutouts and discovered one had blown, which prevented the machine from heating up and caused it to freeze on the "rinsing" screen [11:10].
• Successful electronics fix — Installed a salvaged thermal cutout from a parts machine, which restored electrical continuity and allowed the system to bypass the startup error [18:15].
• Persistent water leaks — The machine was diverting water into the waste tray instead of the coffee nozzle, indicating degraded internal seals.
  • Initial repair failed when generic O-rings could not withstand the machine's 15 bar of pressure [27:29].
  • Final resolution involved replacing the entire upper piston assembly with one from a spare unit [29:07].

How does the thermal fuse assembly operate?

Why did the initial attempts to stop the leaks with generic O-rings fail?