I am installing a new heater / exhaust / light combo in my bathroom to replace a previous one.

There is already a three pole switch. It's wired like so.

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It has two black, and a white wire coming out.

I've placed the new unit in the ceiling, and connected all of the grounds. There's two electrical cables going into the exhaust fan.

One on the left side looks like a normal three wire heavy interior romex wire with a white, black and ground. This was very straightforward and connecting it made the heater work with the appropriate switch when I turned on the circuit again.

enter image description here

However the right side supply is much more confusing. It should be connected to the two additional outlets in the unit, for the fan and light. The wires from these outlets are blue & white and black & white. Here's the diagram for it from the manual.

Now, the second line coming in to the box is only three wire, ground / black and white.

How should these three wires connect to the four in the box? The ground goes to the ground, makes sense, but that leaves a white and a black from the supply to connect to the four outlet wires : blue & white and black & white.

I DO have a multimeter but I am not sure how to use it and figure out what to do with these wires.

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**Edit ** now that I've thought of it more, if the power to the heater already works, just from the left side wiring, then somehow the three wires going in to the box are working with the switch on the wall. I'm not sure what this means

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  • 1
    It seems they replaced the red with a white at the switch which is allowed if the white has black or red marking at each end. The white at the switch seems to be a switched hot, when it should be used as the live hot(connected to a black in a box). More pictures of the other boxes will be needed to help/see what is going on.
    – crip659
    Nov 20 at 23:56
  • 1
    Neutral must be white, but white does not mean neutral. Switches do not/bad if they use neutral. Connecting non-neutral white to a neutral white is not good.
    – crip659
    Nov 21 at 0:16
  • Something doesn't add up here. Could be just confusion. Could be some switched hots not having always hot or neutral in the same cable. Could be ground was used as neutral. Pictures of the original fan wiring would be really useful, but I suppose it is a bit too late for that.... Nov 21 at 1:21
  • Can you post photos of the wiring in the various boxes involved please? Nov 21 at 3:48
  • Hi @ThreePhaseEel and crip659 , I've added a photo of the inside of the unit and its wiring now
    – FoxDeploy
    Nov 21 at 17:09


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