"...there are only 2 black wires, and 1 copper wire (ground). The instructions say i have to hook up the white wire to a set of white wires in the junction box. but there are no white wires in the junction box." I'm a bit confused by this description. Did you mean that there are 2 black wires, 1 copper wire and 1 white wire?. That's what would make sense. Assuming that's the case, here's the deal: There are a couple of ways switches can be wired. One way is that the power feed first enters the switch box with both a hot (black) and neutral (white). The neutral is simply passed on to the fixture (i.e., the incoming white is connected to the outgoing white). The incoming hot connects to the switch and an outgoing hot goes to the fixture. (So, two wires in, two wire out, right?) A second way is that the power feed goes first to the fixture. The white (neutral) connects directly to the fixture and the incoming hot goes to switch along with what we'll call a "return" wire. This is known as a "switch loop" and it has no neutral. One wire is "always hot" (the feed) and the other is the "switched hot" because it only gets power when the switch is on. [There are a couple of other ways to wire a switch, but these two are the most common.] A simple switch does not consume power itself. It only connects the two wires then it is closed ("on") and disconnects the two when it is open ("off"). The problem arises when a more complicated switch needs power for something. For example, a switch with a pilot light or night light consumes power itself and so it needs a neutral. Ditto with some timers. You cannot wire a switch that is itself a power consumer to a simple switch loop, which is apparently what you have. So, there are two possible solutions. First is to do some rewiring to bring a neutral into the box. One way to do this is replace the switch loop cable (two wires) with a three-wire cable, one of which will connect to the neutral at the fixture. Since you're not familiar with wiring, I won't elaborate on how to do this, or other ways this can be accomplished. You'd probably need an electrician. A second possible solution is to find an old-fashion mechanical timer that doesn't use electrical power itself. (It's basically a switch with a "wind up" spring.) This assumes, of course, that your intended purpose is just to let the fan run for a while and then switch off by itself. If your objectives are more sophisticated than that, I'm afraid you're SOL. Good luck.

I have experienced this issue (fan randomly coming on in the night) and believe I have found both the cause and the solution and would like to share it with you. Firstly this is to do with an inline fan system where the fan draws air out of a shower light assembly and then pushes it out through an external vent. The problem is moisture getting into fan timer electronics which causes the circuit to switch the fan on, sometimes with irregular pulsating speed. The solution will be to remove the timer circuit board and dry it out. However, you will need to make sure it doesn't happen all over again. There are two things I did in an attempt to make sure the problem didn't reoccur: 1. The wires from the fan (the fan is in the moist air flowing along the pipe) connect to the timer circuit through a channel in the fan housing. Air can also travel along the wire channel bringing moist air with it where it condenses. Use a sealant to block the channel before replacing the timer circuit board. 2. The air will be forced down the wire channel if the outside vent becomes blocked - it will try every route to escape. Keep the outside vent clear. In my case it was blocked with lint and fluff. Hope this helps

I believe the fan itself is one that operates on ambient humidity. Mine is a Panasonic Whisper and it works quite well. I had to adjust because it was over-sensitive when first installed but after adjustment it turns itself on when someone showers and then turns off sometime later automatically. I also have motion detector lights in the guest bathroom - required here but still handy since I might not otherwise be aware of lights in the guest bath that are left on. The only negative is I have a friend who is fond of my sconces which are not motion detection wired and she will turn them on for atmosphere :-) and then I won't realize they were left on.

Yes I've asked them to send an electrician over to check it out but he's not available until mid-August. I thought it might be a simple fix to handle myself and save them the trouble. I wouldn't mind something sensor-based, if the fan is powerful and efficient enough to handle moisture without running continuously, but I don't see any sensors at all. By all indications it just runs 24/7 when I connect power to it.