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Why does a 6"extractor fan with timer make a humming noise when not running

2 Answers from MyBuilder Electricians

Best Answer

Hi there.
You may find that it’s the transformer (if there is one) and not the fan itself.

Transformers sometimes do hum slightly, and a way of stopping this or softening it, is to fix them down with a good fixing. Normally simply by pushing the cover on them does this too. In effect, electricity is jumping from one coil to another and this causes the hum.

If it is the transformer, first Isolate power and ensure it’s isolated correctly, remove the transformer and apply a little silicone underneath it to act as a shock absorber. Tighten the screws firmly.

There are two lives to a timer fan. One is switched and the other is permanent. The permanent one is used for the after run timer function. I presume that the fan is working correctly?

If it was energised and trying to run with a blockage or a bent shaft, then this could also cause it to hum.

Another thing it could be is a bad connection. This could cause arcing (where electricity jumps from one pole to another) which could also make a noise. This is more a crackle though than a hum.

Just ensure to take care and to Safe Isolate the mains.

Hope this helps you.


Answered 13th Nov 2012

This is the motor drawing electrical current in the windings in an effort to try and turn the stuck blades of the fan. Normally the motor will burn out after a while and the humming will then stop.

If you can clean/free the fan blades and check for debris/obstructions, so that the blades can spin freely its likely that the fan will work properply again.


Answered 13th Nov 2012

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