Panasonic bath fan won’t turn off

[Kolledog]

I have a Panasonic fan/ light in my bathroom, model FV-05-11VKL1. Fan has a humidity sensor that turns on the fan when someone showers. Fan is also controllable from a wall switch. Worked great for years, and then this summer, the fan ran for longer and longer. It got to the point where the fan would never shut off.

i ordered a new humidity sensor— fan keeps running.
I took the fan apart and cleaned out the dust—fan keeps running.
I took apart, cleaned, and put back together the duct work—fan keeps running.
I pulled the double wall switch (one for light, one for fan) and checked it with my fluke meter, thenput everything back together—fan keep running.

i ordered the same fan new from an hvac guy on ebay, installed it, AND THIS FAN KEEPS RUNNING TOO. WILL NOT SHUT OFF. JUST LIKE THE OLD FAN.

i dont know what else to try. Voodoo? An exorcism?

any suggestions would be greatly appreciated. Thank you!

 

[wwhitney]

Are you sure nothing changed with the wiring at the fan or at the switch?

This type of fan needs constant power so its internal modules can turn the fan on or off as required (some them can even have a high and low setting, and automatically run at low at a specified duty cycle up to 100%). And then it has two red wires that are used to tell it when to turn on or turn from low to high. While the internal light is basically a separate load with its own hot and neutral--sometimes two hot connections (black and blue) if there is a night light.

The upshot is that how you do the wiring at the fan and at the switch can vary a lot, depending on how many wires are run between the locations. And if the fan was retrofitted from an older install which might have used fewer wires than optimal or than a new install would use, one option to control the fan via its red wires while using only one wire from the switch box to the fan is to install a small 3rd party relay at/near the fan. That would take switched power from the switch location and use it to either connect the two red wires together, or not, depending on whether switched power is present.

So on the off chance you have an auxiliary relay like that, your results would be consistent with that relay failing closed, so that the red wires stay connected together regardless of what signal you send it, and the fan runs all the time. But that's a total guess, I expect there are other miswiring arrangements that could cause the symptoms you report.

If miswiring is a possibility, you'll need to post a diagram showing both ends of the cable(s) between the switch location and the fan location, and how each conductor in that cable is connected to what at each end.

Cheers, Wayne

 

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[Kolledog]

Thanks, Wayne, for your considered reply. JUst say it now...
Nope, nothing changed at the wiring or the switch. That's what's so weird about the whole mess/