I have two devices that started to work constantly. That is I can't turn them off. They just run all the time. The switches don't do anything.

The two devices are the the ventilator and air-exchanger in the bathroom:

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And there are two twiches that control them (respectively):

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Now to the amazing part.

When you switch off the circuit break for the ventilator in the ceiling (the circuit break for the on/off switch), then the ventilator stop running but the air-exchanger still continues to run.

When you turn off the circuit break for the air-exchanger, the air exchanger stops running and the ventilator in the bathroom is now controllable with the on/off switch.

So my conclusion is that the controller for the air-exchanger is broken. And that the air-exchanger is hooked up to the bathroom-fan to control it too.

What bothers me is that why the fan stops when I turn off the break for the on/off switch? I mean if we agree that the air-exchanger has control over the fan too, why disconnecting the on/off switch stops the ventilator?

When the circuit-break for the air-exchanger is off, the ventilator is controller by the simple on/off switch.

| CB air-ex | CB vent | Swch Vent  || Vent  | Air-ex |
| ON        | ON      | ON         || ON    | ON     |
| ON        | ON      | OFF        || ON    | ON     |

That's ^ obvious. As I said the devices run constantly. The "switch" for the air-ex never does anything at all. It's not even included in the table.

| CB air-ex | CB vent | Swch Vent  || Vent  | Air-ex |
| OFF       | ON      | ON         || ON    | OFF    |
| OFF       | ON      | OFF        || OFF   | OFF    |

When the CB air-ex is off, the control comes back to the on/off switch. So now you think that the "priority" controls is the air-exchange. Okay. See this:

| CB air-ex | CB vent | Swch Vent  || Vent  | Air-ex |
| ON        | OFF     | ON         || OFF   | ON     |
| ON        | OFF     | OFF        || OFF   | ON     |

If you turn off the CB to the ON/OFF switch, the ventilator is off.

So why, when the CB vent is off the vent is off, but when the on/off switch is off, the vent is on?

Thanks kindly in advance for your thoughts and comments.

P.S. This started after the house got hit by lightening.

  • Before the house was struck by lightning, did the ventilator and air-exchanger operate completely independently from each other, or was there some interaction between their controls? Aug 5, 2017 at 3:37

1 Answer 1


Turn off the breaker for the 3 switches and remove the cover and see if the wiring is burnt. The switch is likely shorted in the on position so only cutting power at the breaker will de-energize the circuit. And since switches are controlling the wrong things but in the same switch box there is likely wiring fused together somewhere. Follow your nose

  • The question is: why cutting the break for the on/off switch stops the fan when there is also control coming from the air-exchanger? At the same time, putting the on/off switch to off has no effect when the air-exchanger is running. That's what is bothering me. Aug 4, 2017 at 20:42
  • I mean, I agree. Ofcourse something got fused together. But I want to understand why the on/off switch doesn't affect the ventilator but switching off the break for the on off switch stops the ventilator. That's weird to me. Aug 4, 2017 at 20:53
  • Are they wired in series?
    – Derek
    Aug 4, 2017 at 20:58
  • It gets its power source before the switch. So it's always hot. Only thing I can think of at the moment
    – Derek
    Aug 4, 2017 at 20:59
  • Ground before the switch is what I meant. Sorry
    – Derek
    Aug 4, 2017 at 21:02

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