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Fused spurs and isolators: what to check first

A fused connection unit (FCU), often called a fused spur, or an isolator may control an appliance without being the cause of its fault.

Written and checked by Willesden Smart Homes. Last reviewed August 2026.

Ask about the spur or isolator Sockets and switches

We serve homes across NW London after checking the postcode and the job. See the Areas page .

Check only controls intended for everyday use: the wall switch, pull cord, appliance controls, timer or settings described by the manufacturer. Note what the point controls and whether nearby power still works. Do not open the fused spur, isolator, fan or appliance, and do not change an internal fuse.

Checks you can make without opening anything

  • Only use the normal controls when the point and appliance are dry, cool and undamaged. For heat, scorching, a burning smell, buzzing or crackling, sparks or smoke, a shock or tingling, water, or repeated trips, stop using the point and do not test the appliance again.
  • Identify what the point controls and note the normal switch, pull-cord, timer or indicator positions.
  • Check only the user controls and normal reset steps in the appliance maker’s instructions, and note whether nearby lights or sockets still work.
  • A safe exterior photo is optional. Keep covers in place and never touch bathroom equipment with wet hands.

Is the fault in the point or the appliance?

  • A competent check separates the power arriving at the point, the spur or isolator and the connected fan or appliance instead of guessing which part has failed.
  • Like-for-like replacement is suitable only when the accessory is confirmed faulty and the box, cable, location and appliance it supplies remain suitable.
  • If the electrical supply and control point are sound, the appliance may need its own service or repair rather than another electrical accessory.
Official sources and further guidance

Need a first check on a spur or isolator?

Tell us what the point controls, what it is doing and which nearby lights or sockets still work.

Ask about the spur or isolator See sockets and switches