Bathroom fan problem - weird wiring

[cyberbub]

Hi all,

My bathroom fan has started coming on continuously, whether the bathroom light is on or not. The only way to turn it off is via the isolator switch outside the bathroom.

I've checked inside the isolator switch and the wires are secure and tight. I was surprised to see only 1 pair of live wires inside there though. (See photo)

Inside the fan there are 3 incoming wires but oddly they are brown and *black* (so not the newer brown/blue or the older red/black code), plus a grey one which must be switched live (See photo). The brown/black voltage is at 240V at all times when the isolator switch is on (whether the light is on or off). The grey/black voltage is at 240V only when the isolator switch is on AND the light is on. All the incoming wires inside the fan seem to be firmly fixed to the connection block.

You've probably gathered that I'm not an electrician LOL. It seems to me that as the grey/black voltage seems to be working correctly, for some reason when it's zero (ie the light is off) it's not blocking the current from the power connection.

Any assistance with diagnosis would be appreciated. Do I just need to buy a new fan?

Thanks!

 

[Taylortwocities]

How are you reading the voltage? You need to be testing with a two probe volt tester to ensure that the neutral is actually in place.
The three core cable is correct brown grey and black. It is the standard to use grey as neutral, but there's no law about it.
That cable must come from somewhere else as it does not appear behind that switch.
If you havent changed any wiring then it can only be the fan at fault.

 

[cyberbub]

How are you reading the voltage? You need to be testing with a two probe volt tester to ensure that the neutral is actually in place.
The three core cable is correct brown grey and black. It is the standard to use grey as neutral, but there's no law about it.
That cable must come from somewhere else as it does not appear behind that switch.
If you havent changed any wiring then it can only be the fan at fault.

I've used a two-probe voltmeter yes.

 

[Taylortwocities]

Must be the fan timer board then. They do die sometimes