Our bathroom fan recently stopped working. Even when the switch is on, it didn't turn at all. No motor hum either, just silence. So we pulled the fan out of the box and tested the voltage in the receptacle: it read only 16V from hot to neutral. I got the same reading from measuring the voltage across the bare white and black wires.
The fan is on the same circuit as the smoke detectors in the house (see photo). I figured this out my having my brother and sister help me out by watching the multimeter reading as I flipped off breaker switches one by one.
The connections, at least to my untrained eye, look fine. So what is causing the low voltage reading? The other bathroom fan receptacle reads 120V like I expected.
I also plugged the 'broken' fan into another bathroom fan's receptacle and it started up fine. Spun somewhat slow, but I think it's a little gummed up after 20+ years of use. So I know the fan is okay, but we still might get another one or at least give the poor thing a good de-dusting.
Thanks in advance for your help.
*Edit #1 I did some more circuit testing. Something I didn't mention before was that in the fan receptacle neutral to ground read 3V. What is interesting is that in the upstairs alarm receptacle, the neutral that reads only 16V also read 3V to ground. The other 119V one read 0V to ground as it should. Hot to ground in the alarm receptacle read 120V as it should.
Edit #2 My dad came home and I told him what I'd figured out today. We will be going into the attic next week to see if we can find the fault. Thanks everyone for your help! Edit #3 Just to be clear, the two photos of measuring voltage from hot to neutral are in a fire alarm receptacle that comes earlier in the circuit. The two neutrals were tied together, along with the small wire that goes to the little three prong plug for the alarm. I only separated them to see if I got different voltage readings. So I don't think a floating neutral is the issue.
FINAL EDIT Thank you manassehkatz for your patience with my repeated misunderstanding of what you were saying. The receptacle is back to 120 and the fan will be promptly reinstalled. For those curious, the issue was in the smoke alarm neutral connection. The white neutral wire reading 16V (as I incorrectly called the bad neutral) must have somehow worked itself loose either over time or when it was jostled around at some point. Once I tied the wires together properly, I read 119V hot to neutral in both the smoke alarm wires and in the exhaust fan receptacle. Woohoo!