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caliscott
low voltage in bathroom exhaust fan

I would like to repair an exhaust fan in a bathrooom.

The fan does not turn on when the swich is flipped. The light switch on the same fixture (it is a leviton dual switch fixture) works fine.

I began with the fan, as it is probably 20 years old. I opened the fixture from the bathroom side and found that the fan is mounted into a recessed fixure and then plugs in a 2 prong receptacle contained in the fixture.

I removed the fan, motor, and plug and cleaned all the fluff from it. I then plugged it in a different wall outlet and it worked.

I then reinstalled it, and it didn't work.

I measured the voltage at the receptacle in the fan fixture at 40 volts. I took apart the fan fixture. I removed the wire nuts connecting the house line to the internal receptacle in the fan fixture. With the wall switch on, the house line measured only 40 on my volt meter. The identical fan in the other bath measured 120.

I decided to replaced the switch. The wiring in the box has the hot wire enter via a GFCI and then act as a common to the 2 circuit switch. One then operates the light fixture in the BR (which works) and the other goes to the fan.

I replaced the 2 circuit switch. The light worked and no fan.

The receptacle in the exhaust fan fixture still showed low voltage.

I then got in the attic and inspected the romex, which is intact for the few feet I can trace it before it dives down in the wall.

What is my next step? It is a short in the house wire? Is the GFCI somehow limiting the fixture?

JLMCDANIEL
Re: low voltage in bathroom exhaust fan

Did you check both the hot and the neutral connections? It sounds like you have a high resistant connection. Do you by any chance have aluminum wiring?
Jack

caliscott
Re: low voltage in bathroom exhaust fan

In terms of checking the hot and the neutral, would I check the black wire to the ground and then the white to ground? I only checked the black to white across the volt meter.

The wiring is copper.

Scott

JLMCDANIEL
Re: low voltage in bathroom exhaust fan

Check the black to ground, if you have 120 volts then the problem is the neutral. When you checked at the fan, did you remove the wire nuts and see if you had 120 volts on the bare ends of the white and black? It's possible that the receptacle in the fan case may be corroded.
Jack

NEC
Re: low voltage in bathroom exhaust fan

1. What are the voltage readings at the switch?

2. Is the switch to the light in the fan on or off when you measure the 40 volts at the fan recept?

caliscott
Re: low voltage in bathroom exhaust fan

I measured across the switch and the working light measures 120 v. The lower switch for the fan motor reads about 40.

The measurements at the fan were with the switch off. That is, with the switch off, the measurement at the receptacle in the fan box is zero. With the switch on, it is 40ish. I can recall the exact number.

Thanks,

NEC
Re: low voltage in bathroom exhaust fan

You need to figure out how to get 120 to the line side of the switch to the fan.

You are using a digital meter and the 40 v means nothing. It is an induced reading and has no available current.

If you do not have 120 on both line and load side of the switch when they are in the on position you have a problem with the switch.

JLMCDANIEL
Re: low voltage in bathroom exhaust fan

You don't measure across a switch. Take a reading from the switch both sides to neutral. When you read across a switch you should get 0 volts if it is on and it could be anything if the switch is off depending on the load connected to the switch. If you read 120 volts from the switch to neutral with the switch is on, move on to the end of the run at the fixture and check the voltage at the wire nuts then on to the receptacle.
Jack

caliscott
Re: low voltage in bathroom exhaust fan

NEC

You anticipated my post. I measured the voltage across the hot wire to the common wire at the fan and across the switch.

the readings were confusing at first - 25 volts on the 1k setting, 25 on the 250 v setting, 5 on the 50 setting, and 1 on the 10 setting. It looked like an artifact of my analog volt meter.

I used the connectivity function (buzzer) to check the line from the switch to the outlet in the fan housing. It is intact.

My only current idea is to check the common and trace it out.

I think I will end up fishing some new romex down through the wall. Anyone have any tips about it?

Scott

NEC
Re: low voltage in bathroom exhaust fan

Before offering advice on how to fish new wire I would still like to know the voltage readings at all points on the switch.

caliscott
Re: low voltage in bathroom exhaust fan

Here is a diagram of the problem switch.
When I remove the wire nuts at the broken fan fixture, I can measure a current at about 25 volts from black to white. On a whim, I reset the volt meter to AC1000 v, AC250v, AC50v and on each of these setting, the needle moves the same distance.

Across the GFCI, it measures 140 v, across the working light switch it measures 140 v, across the switch to the fan is measures 25V, but it is the needle deflection as described above.

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