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This post is continuation of my other post How can I remove stripped screws in a bathroom exhaust fan motor bracket?. I was able to successfully remove vent fan and test in a regular outlet and it is working fine(https://i.sstatic.net/1nNfO.jpg). That means, there is no problem with the fan.

Now, I start troubleshooting what could be the problem with the electrical outlet and I don't see anything wrong. Checked electrical joints in the below picture and don't see any corrosion or burnt sign: enter image description here

Checked using multimeter NCV to see if outlet is receiving power and seems fine: enter image description here

What could be wrong with the power supply as everything seems fine.

EDIT: Here is the voltage measurement 4

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  • It is thermally protected. Check the thermal switch. There might be interrupt. It looks like the white wire does in to the thermal protection switch. Thermal protection switch work with one wire passing true to the other side, until switch interups it.
    – Traveler
    Jun 1, 2022 at 3:00
  • A non-contact tester doesn't help you here. You need to know if both hot & neutral are present. Poke the meter's test leads into the socket and see what you get.
    – brhans
    Jun 1, 2022 at 3:11
  • @brhans Updated my post with voltage reading.
    – javanoob
    Jun 1, 2022 at 3:25
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    @javanoob the fan housing says it is thermaly protected. I have no more info from you but see the white wire going into the black plastic box. I assume that is the thermal switch. Thermal switch work with one wire going in and one going out. If thermal switch is activated that connection is interrupted. It is not the plastic red caps.
    – Traveler
    Jun 1, 2022 at 3:35
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    @javanoob The way to test thermal switch is to disconnect the in and out wire and use Ohm meter to see if it is closed or open. Some thermal switch do not recover and stay open, and has to be replaced. To test it just bridge the in and out with a pice of wire.
    – Traveler
    Jun 1, 2022 at 3:39

2 Answers 2

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Thank you for the photos. One is missing, the fan unit itself.

Since you have power everywhere it should be, the culprit might be the thermal switch. The unit is thermally protected.

It is usually mounted on the fan unit, on the motor to protect from overheating and starting fire. Most thermal switch do not recover once activated and need to be replaced.

You can identify it by looking for one wire in one wire out (usually same color) mounted on the motor.

label indicating that the fan has thermal protection

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  • For clarity, the "thermal protection" is, effectively, a heat activated fuse/circuit breaker. Some are like a circuit breaker that can be reset manually or may even reset themselves, others are like fuses that, once blown, must be replaced. The implication here is that this is either a fuse-style one or a manual-reset style and that the OP must find the thermal protection and reset or replace it.
    – FreeMan
    Jun 1, 2022 at 13:11
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This situation is resolved and I wanted to post how it happened.

  1. My wife was doing bathroom cleaning and used bleach.
  2. After the cleaning, vent fan stopped working. Not sure if it is a coincidence or anything to do with bleach. One thing to note is that she used undiluted bleach.
  3. And then I removed the fan, thinking it is time to replace it.
  4. But when I checked fan in other room by plugging it in outlet, it was working fine.
  5. Then I started looking at the wiring to find anything obvious. While doing that, I turned off main for bathroom.
  6. I turned on main for bathroom and as a final step, I plugged the fan into the outlet and it started working.

So, my guess is turning off and on the switch for bathroom at breaker box might have reset the fan outlet.

Also, in the above post where I am taking voltage reading of outlet with multimeter leads is after I turned off and on the switch for bathroom at breaker box.

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    I wanted to delete this post completely as it got resolved with no real fix but still wanted to post exactly everything what happened as it might help others. Not sure if that breaks rules of this community.
    – javanoob
    Jun 1, 2022 at 17:11
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    Self-answers are certainly accepted. Also, "beats me but it works now" at least brings closure. Be sure to give yourself a check mark as soon as the system allows you.
    – FreeMan
    Jun 1, 2022 at 17:29
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    If the breaker ("the main") is a GFCI breaker, and if undiluted bleach was sprayed on the fan switch or any outlet on the same circuit, this could have caused a ground fault and popped the breaker half-way. Straight bleach is an excellent conductor of electricity. With the GFCI tripped, it would seem like the fan is dead. When you turned off the breaker for safety, then turned it back on later, you reset the breaker and restored power. Good that you tested the fan in another outlet before replacing it!
    – MTA
    Jun 1, 2022 at 21:23

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