Dimmer switch prevents extractor fan timer from working?

Question

Hi, I've installed a pull cord dimmer in the bathroom which controls the 3 looped low voltage light transformers. The problem is that although the extractor fan comes on when the lights are on, the timer fails to turn the fan off when the lights are off. The only way to stop the fan is to interrupt the permanent live going to it. The switched live is coming from the dimmer pull and being a dimmer still leaks current to the extractor even when the lights are off. I don't want to replace the dimmer with a standard pull switch. Is there anything out there that I can install between the dimmer and the switched live of the extractor that will prevent any input to the extractor if the output from the dimmer falls below a certain threshold? ie: Undervoltage Lockout or similar?

This is now starting to really peck my head!! Any advice would be greatly appreciated.

Thanks

The Natural Philosopher · Accepted Answer

Ah. I assume these must be electronic transformers then?

Its odd, because all my dimmers (rotaries) actually DO interrupt the live when actually switched OFF, not merely reduce it to a trickle.

However, if what you say is true, the addition of some form or resistive load - say a low wattage mains light o the bulb sort - in parallel with the LV stuff - should pull the voltage low enough to fool the timer.

But I suspect some mis wiring is in this equation..because I have yet to meet a dimmer switch that applies any live to the electronics when actually switched OFF.

Andy Wade · Answer

But this is a pull-cord dimmer. I've no idea how those work, but maybe there's no hard-switched off state? That being the case a suitably mounted 33 or 47 k ohm 2 watt resistor across the output (SW-L to N) might do the trick.

Dimmer switch prevents extractor fan timer from working?

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