help [installing bathroom fan]

: installing a bathroom fan hook up the wires black to black than white to white and the switch is off ad the fan runs, than turn the switch on and blows the fuse

Reported for forum change.

Thread moved to GQ from ATMB, and title edited to indicate subject.

General Questions Moderator

Are you installing or replacing? Did the old one work?

If you are replacing, and the old one worked, you most likely have a short to ground somewhere. Re-check your wiring. Open the junction box for the fan and see if and of the wires came undone and one of them is now touching the metal. If you did anything with the switch, check for the same thing in that junction box.

It’s possible the fan is also to blame, but not as likely, especially if it’s new.

If you made all new wiring, you’ll have to check for a short somewhere in your wiring as well. This can be done easily with a continuity checker.

I just re-read the OP and missed the part about the fan running when the switch was off.
Disregard my last post

You’ve got something wrong with your wiring, it’s going to be difficult to troubleshoot over the internet.
My WAG, is that someone (you?) tied a bunch of black wires together thinking they were common, on top of that they were probably on opposite phases. Turning the switch on, connects two hot phases and blows the breaker. Out of curiosity, are you blowing more then one breaker at a time?

What color wire goes through the switch, it should be black.

I’m thinking you have two black wires coming from the breaker box, one of them goes to an outlet (or bathroom light on another switch) the other through the switch. After it leaves the switch, (I’m guessing here) it’s connecting back up with the other black wire and going up to the fan. If this is indeed the case, when the switch is off, the fan will be getting it’s power from the unswitched black wire all the time. When the fan is switched on, it will get it’s power from both wires. If the wires are coming from opposite phases, the fan is going to be getting 220 instead of 110.
As I think about this “outloud” this is the conclusion I’m coming to.

The only other thing I can think of is that the switch is bad.

is the switch on the fan?
is the switch a wall switch?

need more details about the whole situation.

Here’s a thread from November about the same thing. Only it spontaneously occurred. There is a lot of advice as well as a resolution.

Yes the old one did work,k got a tester there is a white and black that come into the bathroom from a light in the next i have white and black tested the wires black is hot now the white black on the fan than there is a white and black to the switch.the fan run when the switch is off turn the switch on and blow a fuse.

This is electrical work, the possibility of hurting yourself is real. You’re going to need to do a better job of explaining yourself, at least before I’m going to take a stab at it.

They come from the light? That wouldn’t make sense unless the light in the other room is on a pull chain. Otherwise your power source to the fan switch would be switched. I assume you mean they come from the hot side of the light switch in the other room.

I got nothin’. This is gibberish and if you’re not going to try and make decent English out of it, I’m not going to walk your through re-wiring your bathroom.
You need someone to come and take a look at this. It appears to be over your head and you’re not doing a good job of explaining it. Do you have a buddy that’s handy with a voltage tester and a screwdriver?
ETA, if the old one worked just fine and the new one is acting strange, the problem is almost guaranteed to be in the area that you worked in. If, for example, you never opened up the switch box, it’s probably not in there. Somewhere along the lines you wired something differently then how it was to begin with and you created a dangerous situation (the reason your breaker is popping). I still think that when you turn the switch on you’re connecting two different phases. The black wire in the box connected to the fan should only be hot when the switch is on. Somewhere, you crossed a hot. Re-read my second post in this thread, I’m still guessing it’s what you did.

tested the wires the black coming in from the light in the room beside the bathroom is hot,now tested wires going to the switch nothing.

Here’s what I presume you have:

Live wires from the other room: black and white.

Two wires coming from a switch: black and white.

Two wires on the fan: black and white.

In reality both wires coming from the switch should be black, because you only switch hot wires, not neutral wires, but some electricians will save money and time by running only one pair of wires to the switch. Follow this diagram and your problem will be solved.

                                |       |
                                |       |
                                B      W                       
                                |       |-----------W-------------|
     |-------------B------------|                                 Fan
Switch                                                            |

Close enough. Mark the white wire coming from the switch with black electrical tape at both ends to indicate that it is a hot wire, not a neutral.

mjh128 your statements make no sense to me, make single small complete statements. start describing what was, then what is now, then what you did try.

where are the switches on the wall or fan? what are the wire colors, are they solid or striped?

Leaffan…i want to thank you much…IT WORKS the way u said…thanks

You’re welcome.