Problems w/ vent. fan in attic


Old 04-16-06, 05:24 PM
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Question Problems w/ vent. fan in attic

I was just in my attic, and for some reason the exhaust fan in the attic is not running. It has a button on the box for the fan to "press to test". However, whenever I press the button, nothing happens. The power supply for the exhaust fan comes out of a junction box in the attic. I have no idea which circuit this is on in the breaker box in order to make sure the power is off before I begin working on it. I do have a multitester, but it has been so long since I've used it, I could use a refresher course. I'm stumped....any ideas or suggestions?? Is it reasonable to assume that the light in the attic and the fan are on the same circuit?? The light in the attic DOES work, by the way...any thoughts or ideas appreciated..

Last edited by tool73; 04-16-06 at 05:39 PM.
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Old 04-16-06, 05:45 PM
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Shame on you for not knowing what circuit the fan is on. You should know this. You should know this for EVERY receptacle, light and electric device in your house.

The problem is that the fan is most likely burned out. Happens all the time. You need to verify power to the fan. Put away the multi tester. To use one you need to know how to use it, which you do not. You also need to know how to interpret the results. Instead, buy a simple two wire tester that has small light bulb and two probes.

Last edited by racraft; 04-16-06 at 08:18 PM.
Old 04-16-06, 05:50 PM
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Shame on me??? The breaker box is not labeled and without tracing the line through all the crawl space back to the box I don't know how I would know. I just moved into the house and did not do the wiring.
Thanks for the criticism though.... that was extremely helpful.
Old 04-16-06, 06:39 PM
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> The breaker box is not labeled

Okay, shame on whomever.

> I just moved into the house

Did you have a walkthrough? Do you own it?

Anyway, a multimeter really isn't the greatest tool.
I like a simple probe with a single point of contact for testing for voltage present. A non-contact probe is usually fine if your only interest is whether there is any power to the box.

So you have to guess. which breaker.

I turn OFF the panel's 15 and 20A breakers on the lefthand side.
If the circuit goes dead, then I turn half those back ON.

Otherwise, I turn all those on the left back ON, then turn OFF half of the 15 and 20A breakers on the righthand side.

Usually 5 trips to the panel isolates the exact breaker.
Old 04-16-06, 08:28 PM
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Had you explained that you had just moved in I would not have been so harsh on you. Breaker panels being improperly labeled or not labeled at all is a common problem. Nowhere in your original post did you say that this is a new (to you) house.

Unfortunately too many people move into a house or apartment and don't bother to figure out the electrical wiring. Then they have a problem, like an open neutral or something, and have no idea which circuit breaker to shut off to so they can open the box to even investigate the problem.

For your own safety, and the information could save your life some day, map out your electrical system. You don't need to determine which way the wires run, all you have to do is to is to figure out what circuit breaker controls each and every receptacle, light or appliance. Then you'll know what breaker to turn off to work on a circuit.

As for your problem, bolide and I have both told you to put the meter away. Use another type of tester, a simpler one. Check for power to the fan.

Often, fans are wired to a convenient circuit. This might be a hallway light, or might be a bedroom circuit. In your case, it could be the circuit for the attic light. Follow the wires in the attic. Where do they go? If they go to the light switch for the attic, or to the attic light, then it could very well be on the attic circuit.

If this fan has never worked for you, then it has likely been dead for some time, and the previous owner either knew it and didn't bother repairing it, or perhaps he or she didn't even know it. However, you should have figured this out in your home inspection and then you could have arranged for it to be repaired as part of the sale.

Determine if there is power going to the fan. Shut off your main breaker if you have to, and work by flashlight. If you have power to the motor, then consider the motor to be bad, and look to replace it.
Old 04-16-06, 09:15 PM
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Post Test the motor winding.

You will need two testers to do this job. One is the FlukeVoltAlert.
and the other is a Wiggy Both can be purchased at Home Depot or your local big box store. Please resist any temptation to use your multimeter to do this job.
The Volt Alert can detect the presence of AC voltage through the jacket of a Non Metallic cable. If the cable is metallic then you will have to open the Junction box in order to conduct the test. Turn off all electronic devices in the house especially anything that contains a hard drive such as a computer and some digital video recorders. Using two cell phones you station a helper at the panel and yourself and the testers in the attic. Hold the Volt Alert against whichever side of the cable give the strongest signal. Have the helper turn off one breaker at a time until your VoltAlert goes silent and dark. You then use the Wiggy to test the splices in the fans connection box. You probe with one lead under the skirt of the wire nut until it is in contact with the wirenut spring or bare conductor. The other probe is held in a slot in the Wiggy's housing while it is held in contact with the bare wires in the box. If voltage is still present the Wiggy will vibrate in your hand. If no voltage is present you can proceed to open both splices to the black and the white wire while still avoiding contact with the bare conductors. With the splices open test again between the black the white and the bare wires in all three combinations. If the circuit is deenergized then you can pull out your multi tester. Set the tester to ohms and read across the two insulated wires going to the fan motor. Make sure you are testing on the motor side of any switch or thermostat. If the motor winding is open then replace the motor.

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