I bought this timed electrical switch and used it to replace a standard switch that turned on my bathroom vent fan (I'm always forgetting to turn it off and it often will run all day.) after the install, everything seems to work fine, but I could swear the fan is not running as loud / with as much power after the replacement. What could be causing this?

4 Answers 4


The timer you installed is designed for incandescent lights only. They make a timer suitable for induction loads (fan motor) You need to switch it out for the correct timer switch. I made the same mistake myself and getting the correct switch solved the slow fan problem.


If you're sure that there's a big difference between before and after installation, it may be that the switch is faulty. Given that controlling bathroom fans is one of the intended uses of that switch, I doubt that they would affect the speed or power by much (if at all) under normal operation.

I would try reinstalling the original switch to see if I could tell a difference (though this might be very subjective unless you have a sound level meter or way to measure the airflow in the vent), and if so, bring the timer switch back to where you bought it for a replacement or refund.


We've used these times switches in two places so far, with good results. They let you run the fan for long enough to clear the room of humidity, as opposed to turning off the fan as soon as you leave the room. And I've not seen the problem you describe.

However, run a motor in under-voltage conditions and you may cause the motor to overheat, killing it prematurely.

A simple test is to temporarily bypass the switch completely. I.e.,

  • Turn off the power to the outlet.
  • Remove the switch.
  • Use wire nuts to connect black to black, white to white. (Better, if you have a simple two pole switch on hand, wire it in place instead.)
  • Turn on the power temporarily.
  • Verify that the fan is now running properly compared to with the timer, or that you were just hearing things.

After this test, return things to normal, in the end either by returning the timer switch to the store as defective and asking for a replacement, or rewiring the timer in the outlet box.

If you are still worried, a more complete test might involve checking the line voltage to and from the switch, and/or checking the speed of the fan itself, but these tests may well be beyond the tools at hand.


A simple multimeter will tell you what you need to know here.

Disconnect the fan from the switch, turn the switch on, and then measure the voltage before and after the switch. If you are seeing a significant voltage drop across the switch, then it is defective.

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