Attic Fan stopped working

[jdc0222]

Hello - Hoping for a bit of advice here about an attic fan that stopped working

The attic exhaust fan stopped working last year. The wiring runs from another light bulb in the attic, which works fine. The wires coming off of that light bulb first go through a standard looking light switch (does not control the light, but seems control the power towards the thermostat/fan), then goes through a thermostat switch to control the fan, then to the fan itself.

Can anyone tell me how to figure out if it's the fan, the thermostat switch, or the actual light switch that has the problem?

Thanks,
Jon

[normel]

It is usually the fan motor that goes bad. Replacements are available.

[jnaas2]

Turn the power off to the fan and check with a voltage meter to make sure the power is off, if it is you can test the switch by setting the meter to ohms reading and touch the black and red probes to the 2 screws on the switch and see if there is resistance or not. If the meter reads 1 there is infinite resistance, if you flip the switch and it shows little or no resistance then the switch is working right. You can test the thermostat in the same way by changing the setting on the thermostat. The power will go thru the switch first then the thermostat and finally to the fan, you always break the power supply so if your brave you can check the switch and the thermostat with a voltage meter and the power supply on, but this isnt recommended if your not comfortable working around live wires. Put the black probe on the white wire and check the screws on the switch and see if there is power at both screws, if there isnt flip the switch and then check, follow the same procedure for the thermostat. If you want to save some time check if there is power at the fan if there is then you have a bad fan motor

[HayZee518]

look somewhere on the motor nameplate to see if there's something that says "thermally protected." if this is the case the internal thermo protection may have gone south.

[jdc0222]

Thanks for the suggestions on how to check and fix this. I know what I'll be doing this weekend!

[HayZee518]

some fan motors have the thermal device attached inside one end bell. others have the device embedded with the windings which is almost non user replaceable. I have replaced these because I have the tools necessary to re-seal the windings.

[jdc0222]

Thanks for all of the suggestions. I bought a new fan, which came with a new thermostat, for $56 at the big-box store, versus $47 to replace just the fan motor. After 45 minutes of running up and down the stairs to the fuse box, I finally got the power shut off to the circuit, and 20 minutes later, the new fan was installed.

[HayZee518]

good! I'm glad you were able to replace it. now grab that motor and tear it apart. look into why it didn't work. you may find the thermal o/l shot.