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mysterious wiring problem bathroom fan

Posted by kisu (My Page) on
Tue, Aug 12, 14 at 22:00

mysterious wiring problem with a bathroom fan switch.

The wires are NM romex style, but are probably about 26 years old. This is a 2 gang box with one toggle for a separate light switch and one toggle for the separate vent fan.

Original simple single pole toggle switch was working and I was updating it to a new decora style single pole switch.

Original switch had black hot wire in bottom screw and another black wire coming out of the top screw that is only hot when the switch is turned on.

The hot wire going into the bottom screw was actually a pigtail from a hot "White" wire that was feeding both the separate light switch and the fan switch. No idea why they used white instead of black to bring power in.

Here is where the mystery starts: I also noticed there is a white wire in the back that is part of the wires for the vent fan and that white wire is TIED together with the ground wires.

Naturally, I separated the white wire from the ground wires, and then proceeded to install the new switch with that same 2 original black wires that were on the original vent fan switch.

Guess what, the fan did not work. However, as soon as I touched the white wire BACK to the ground wires, the fan started working again.

(1) WHAT is going on?

(2) How do I safely repair this without taking the ceiling fan out?


Follow-Up Postings:

RE: mysterious wiring problem bathroom fan

The hot "white" wire is tradition for the feed from a switch loop (this is OK).

The white going to the bare grounds is NOT OK.
My guess is that originally this only had the switchloop in it (probably for the light alone) and someone kludged in the fan circuit as a non-switch loop. The problem is while there was a hot in the box, there was no neutral so the IDIOT connected the fan neutral to the ground.

You need to fix this:

1. Either run power (hot, neutral, ground) to the fan and use what's running to that box as a switch loop (similar to what you have for the light switch)


Run proper power (hot, neutral, ground) to the switch box for the fan. This is actually what is required by the later codes.

RE: mysterious wiring problem bathroom fan

Hi Ronnatalie,

thanks for the advice.
Question: how did this fan operate for 26 years with the fan neutral being tied to the bare ground wires.
Also, the 2-gang box the fan switch is in is is metal .
was anyone ever in danger?

RE: mysterious wiring problem bathroom fan

It worked and nobody got shocked because neutral and ground remained at the same potential for 26 years. If the grounding connection back to the main ever became compromised then the switch box and anything grounded to it would become energized. Often it takes two things to go wrong before a problem shows itself, you had the first one but not the second (yet). And yes it is not uncommon for connections to become compromised or completely open, happens all the time.

RE: mysterious wiring problem bathroom fan

As Joe points out, as far as the fan working, it will work that way. It however is a massive safety issue. Not only does it jeopardize safety in the bathroom, but potentially elsewhere that the lighting circuit serves.

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