The 4way suggestion involves another switch. The way you described wires in holes may mean the switches were "backstabbed" and these connections can fail more often than wires that are curled around the screws and held in place by tightening the screw. This failure could have happened in the unknown 4way(s). If you can establish that all of the wires begin and/or end in the two switch boxes or at the fixture then there is no other switch, but, if there seems to be wires that appear from nowhere or disappear to parts unknown, then you may have a buried splice or one or more 4way switches. The black wire that is hot at the dimmer is also hot at its other end unless it's broken, the same holds true for the white at the other switch. One of the common terminals should always be hot, that's the one that comes from the panel either directly or from another accessible splice. The other common should only be hot when power is sent to the light. The two screws that are the same color on the non-dimming switch should alternate between hot/not as either switch is thrown.

"The fixture itself is a fan/light combo where both light and fan turned on at the same time. Is it possible someone rewired the same fixture intentionally (I don't know why though) and turned it from a light-OR-fan to a light-AND-fan? I dunno, maybe they figured they never used one without the other and got tired of turning on both? Would that make more sense?" Ah hah! Yes, I'd say it is all but certain now. The light/fan functions were once separately switched and then someone decided to tie them together on one switch. That means "Plan A" because "Plan B" was based on the (now debunked) assumption that there's only one remaining function in that fan! [Not to complicate things just when we're drawing down to some final conclusions, but it also means you have available a "Plan C", which would be to use a new dual switch and return to the original design, with fan and light controlled by their own switches. Arguably, that might save some energy if the fan is sometimes left running when the light isn't needed or vice-versa. But I'm not pushing that one way or the other; it's altogether your choice!] "I will try as you suggest (requires a hardware store run) but I'd like to understand it better first. What are the fat white wires? Am I right in guessing the dark rubber conduit probably goes to the fixture and the silvery ones are household supply? Ya know, when I looked at the pic with the white wires, I didn't quite understand it either. It looks to me like they are neutrals, but I assumed you'd just chosen to omit some of details, like how the neutrals are wirenutted to each other in the box. One of the missing details about the fan/light is that we never did figure out the source of the neutral for that fixture. With 120V wiring, any light, fan or other outlet needs a hot feed and a neutral to work. These days, most electricians would wire that fan/light combo by running a three-wire cable from the switch to the fan (e.g., black for the switched hot light feed, red for the switched hot fan feed and white for the neutral). My guess is that whoever wired your light/fan didn't have 3-wire cable (or didn't understand how to use it) and so s/he put the two switch legs in one cable and ran the neutral in the other. The fact that both of those cables have rubber sheathing tends to confirm that those were part of the same "project". Why, exactly, there appear to be two white neutrals heading "north" is anyone's guess. It's rather bizzare, actually. Not that it matters much, but I think what you have there are cables (not conduit); conduit is like a pipe with individual wires running through it. If, as I suspect, it's cable, not conduit, the rubber sheathing could indicate that it is submersible pump cable or motor wire or something like that. Very possibly, it was just some scrap wire that someone happened to have laying around. Another possibility is, gulp!, that's a cut-up heavy duty extension cord! I dunno, but it isn't anything "standard" I'd expect to see in a bathroom wired in the 60s (or now either, for that matter!). [Not that I doubt you, but I just gotta ask it again: Are there really two white wires in the same two-wire cable???] The "silvery woven" cables appear to be early 60s vintage "Romex" (a brand name, actually, but often used generically). 1967 was right about the point in time when the woven sheathing was phased out in favor of the plastic-sheathed NM-B that we see today in new wiring. Whatever the ancestry or breed of that rubber-covered wire is, the way I would expect it to have been wired is this: three white (or maybe grey by now) neutrals tied together--one from the feed in the lower left, one to the circuit continuation in the lower right and one to the rubber cable in the upper right. Because a cable with two white wires is quite strange, I'd expect to find, on close examination, a black wire in that cable that's been clipped off and not used. As you've presented it in your drawing though, it's a head scratcher alright. It could be that the neutral runs on one wire to the fan and then back to the circuit continuation but, again, that'd be beyond strange, IMHO. This particular box was apparently ungrounded. The ground wires were twisted together but left loose in the box. All the other boxes I've opened up so far have had the grounding wires twisted together and looped into a tab-like projection on the box (metal), and not on the switches or receptacles. Was this acceptable practice in the past and not now? I was expecting this project to be a simple, straightforward direct replacement project. Geesh. Geesh is right! Nothing short of cucumbers grows faster than a home wiring project. Yes, times have really changed when it comes to grounding. Cables with ground wires included began to appear during the 50s and, frankly, I think a lot of electricians had no idea what to do with them! So they twisted them together and sometimes attached them to boxes, etc. :-) Keep in mind that most receptacles then accommodated only two-prong plugs and switches had no grounding terminals. A lot changed during the 60s, as three-prong outlets became standard by the end of the decade and more and more equipment had separate grounding connections. And the good news is this: Few changes in wiring requirements reduced the number of serious house fires more than the advent of comprehensive grounding systems. And the other good news is: Your house wiring includes equipment ground wires. Whenever you have the opportunity to improve something, put them to use! And, especially, whenever you're putting in a device that has a green grounding terminal, take the time to connect it to ground. (Also, check the connections on the old ground wires to make sure they're sound. Once upon a time, just twisting them together was a normal practice. Modern code requires a mechanical connector such as a wire nut or a crimped sleeve. "I really need to pick up a wiring book. Can you recommend one? I heard that one which was previously highly recommended (and I was going to pick up) is on recall now though. Yeah, that recall caused quite a flap. I'm sorry I don't have a good recommendation on the title of a basic book on the top of my head. Hopefully, someone else will pop in with one.

Hi! Maybe what I was trying to describe is not called a switch loop. Maybe I should have given an example of what I am talking about. Let's take my brother's "den + 2 bedrooms" circuit. The power comes from the panel to the ceiling fixture box via a 14/2 loomex. From there another 14/2 loomex goes to feed the outlets in the den, and another 14/2 loomex goes to bedroom #1. Also, a 14/3 loomex (bare ground + white + black + red) goes to the switch for the den light. At the fixture box, the whites are wire nutted together, and the bare grounds as well, which are also attached to the box and has a pigtail for the fixture. The blacks are wire-nutted together and the red wire (from the switch) is alone. The hot wire from the chandelier is connected to the red wire and of course the neutral from the chandelier goes to the whites marretted together. The hot black wires are just standing there. Then at the switch (which is mounted on the wall separating the den from bedroom #2), there is the 14/3 from the light fixture box and another 14/2 loomex that goes to bedroom #2. In the den switch box, all grounds are wire-nutted together and attached to the box, all whites (neutrals) are wire-nutted together and the two blacks are wire-nutted together with a pigtail that gets attached to the switch. The other leg of the switch is attached to the red wire that goes to the chandelier. I hope this description makes it clear. Please note that I live in Montreal Canada and I have seen this wiring technique at my aunt's house (built 1964) and also at other friend's houses where I helped with wiring or installing light fixtures. Can someone please tell me if it is still allowed, and if I can use more than one fixture wired this way per branch circuit? Thanks a lot.

The only way I can think of off hand to get a pseudo series circuit is if the wires are all pinched together behind the light fixture transfering some of the power. I doubt the wires are long enough to transfer that much voltage under normal circumstances. Unless the metal of the conduit is acting like a transformer, but the ground continuity would probably need to be broken or have a high impedance path back to the panel somewhere. This sounds more likely only because it is effecting all three wires at the same time, even when totally disconnected