This is a stumper...

[Terryl]

OK kids an new one on me, at my sisters house we have a new windows 10 pro PC (a Dell) she called me to come take a look at something strange going on with the computer.

I get there and she says "look at this" she turns the ceiling fan on and then turns it off, the computer makes a short beeping sound, when she turns the fan back one it doesn't do it, it only makes the sound when she turns the fan off.

Now for the weird part, if she does it several times (on/off/on/off several times, and waiting till the fan comes up to speed) the PC actually shuts down.

Now I tested the AC wall socket and there is no direct AC power connection to the fan switch, the fan and PC are even on two different phases on the house AC power.

Also the PC is on a UPS/surge protection unit, and running it's internal tests shows nothing wrong with the unit, also the AC power is at a normal 121 VAC for our area.

This one has me stumped as I have never seen something like this, I could understand if it was on the same leg of the power line, but on a different leg from the fan???

Got me stumped.

[dishuser]

does the fan have a remote?

[Terryl]

No it's on a wall switch only.

[Terryl]

And more info, I tried several other switches in the house, all OK, but the garage lights switch did the same thing, garage is 30 feet from the computer.

I wish I had a power line monitor, this way I could tell if it's a spike on the line or something else...

[runamok]

The leg the fan and computer is on could have a big load on it.I have a standup fan with remote when off you could see fan blade twitch when deep freeze kicked on.

[Highwayman]

i read article on this years ago do you have a hdmi cable one with sheilding
for voltage noise i think it stated certain hdmi cables were causing the problems???

[Terryl]

The leg the fan and computer is on could have a big load on it.I have a standup fan with remote when off you could see fan blade twitch when deep freeze kicked on.

The computer and fan are on separate AC power legs.

I'm looking for someone with a power line monitor, this could tell me whats going on, the funny this is that the PC is on a new APC ups system, and it tests out fine, I even used an extension cord and tried a plug down in a bedroom that's not being used, same problem, also tried all sorts of house hold appliances, the only thing to do this is the ceiling fan..

[Terryl]

i read article on this years ago do you have a hdmi cable one with sheilding
for voltage noise i think it stated certain hdmi cables were causing the problems???

Not using an HDMI cable on this PC setup.

[auggie]

Test PC & fan when PC not hooked to UPS/SURGE protection & see if same result ? sounds like
A ground fault somewhere possible, ?

[hotplay]

Neutral may have a back feed ground fault, something with a winding chances are its the Fan or reostat if using one. Most likely the fan winding.

[staticrider]

Years ago I installed a low voltage line for a Security system keypad. I didn't properly separate the line and used the the same holes on one wall the already had some 12-2 in it. Every time the fan switch was used the keypad would play a short musical melody.

[Terryl]

OK kids here is what I found...After thinking about this I kinda recognized the sound the PC was making when this happened...Guess what it was...It was the beep-ploop noise when you plug and unplug a USB drive or device, so looking at what she has connected, I tried several things, printer, speakers other stuff, what I fount out what it was, was the USB cable from her weather station, unplugging that cured the problems, she doesn't really need the weather station so the problems are gone...Now to figure out why that USB input cable caused the problems.


Thanks to all that help out,

Terryl