Electrical Wiring in the Home/Attic Fan


I replaced an attic fan that was running but noisy. Over the last year we have replaced 2 motors and one entire motor/thermostat and all have burned out the same day. They run while the electrician is there but once it shuts off it never goes back on. Everything has been checked and amp is good, wires good but motors are dead.  
What could this be?  
Thank you!

ANSWER: Tricia,  it runs good while the electrician is there but once is shuts down you cannot get it to restart,          why not have the electrician shut if off and he should be able to troubleshoot it

I am not slamming electrians but they have little training in electric motors,       

Just from your description,    it could be several things:

If the attic is extremely hot for some reason, some motors have an internal thermal,  that is a bi metal switch,   if the ambient temperature is high, up by the ceiling  that switch might be tripping and it only resets when it cools down,      so if the temp of the attic is high, it might take a long time to reset,        I am assuming you are saying the motor does not even try to start or hum  

Next even though the amps are correct,  voltages change in most homes,  I watch mine change from 115 to 121   

I have seen deviations as high as 151 volts,     if you have dimmed looking lights or other issues  it very well could be a problem with you incoming voltage,  for example a loose or corrision on a connection at your transformer,       

If you know the amps,  then you had a line splitter to get a clamp amp meter on one line,  

What is the voltage AT THE MOTOR WHEN IT WILL NOT START?  IS there voltage present?  If so what is it?

Ceiling fans are hard to overload,   so even the wiring could be effected by heat feeding the motor,    that is where you need to start     when it won't start have the electrician measure the voltage at the motor,    if none,  then at the switch  both feed and load sides of the switch   follow it back until you find voltage and the value

Are you putting up the same brand?

You say the switch, thermostat and motor all burned out,   explain,   

Do you take the switch apart and inspect the contacts?

Is the motor an open style where you can see the windings through vent holes,  and the wiring is all black internally  and smells of insulation burning?

Anything else going on in your home that is electrical in nature that is odd?

Low or high voltage,  a voltage spike,  any of those could burn out a motor, but nothing else is being effected so I would be looking at the wiring size,  making sure the connections are correct,    a quick amp check might be deceiving,  ampere checks for this kind of issue need to be of some duration,    maybe the amps are good for a moment but if low voltage or high voltage is present   it might take a while for the amps to creep up,   

Are these the same make and model motors or complete fans?  Same brands?   Does the circuit breaker ever trip on that circuit?

Unless you ran into a batch of just bad fans/motors  voltage readings are now absolute to find the problem   

Let me know if you can get some readings and values when the motor WILL NOT START    then we can go from there         if the motor is right with no defects   then it is something external to the motor    be it the value of the voltage or heat which would be very uncomfortable if was that hot at your ceiling,      some of these internal motor switches are not very reliable,   a few trips and the bi metal looses it's ability to bend and then the motor circuit is open,  not necessarily burnt,     but if you are looking and smelling the motor, see the windings,  and they are black    it has to be voltage      

Let me know what you find,,,,,,  Will

---------- FOLLOW-UP ----------

QUESTION: Thank you for this info will pass on to my electrician.  We decided to put in a gable fan since my house is more set up for a gable fan and run a new dedicated line for the fan.  

He checked everything last weekend and changed the breaker also and everything came out ok.......no voltage issues he could find.

Very good, sounds like you have better air movement, and all is well. If you have any problems at all with the new fan,  let me know. Let's put it on the first fan and now that is no longer needed, problem gone.

But if anything does come up, feel free to let me know.

About Electrical Wiring in the Home
This site answers questions related to home electrical wiring, home wiring, general electrical help,and other electrical questions related to aleternating current (AC). You can find help on the National Electical Code, home electrical issues, wiring electrical outlets, installing lighting, electrical grounding, and general electrical help for do-it-yourself projects not require an electrician. If you do not see your home electrical wiring question answered in this area then please ask your electrical wiring question here

Electrical Wiring in the Home

All Answers

Answers by Expert:

Ask Experts


Will Babbitt


Electrical issues of all types, wiring, control, appliances, components, specialty in Electric MOTOR or APPARATUS trouble shooting, electric motors, electrical problems, single phase, three phase, DC, capacitors, elevator MG-Sets, modifications, reverse engineering, VFD Drives, single to three phase convertors. Repair of most any electrical/mechanical/electronic apparatus, OEM, AC, DC, Industrial Applications, Three phase, single phase failure mode, determining the root cause of the equipment failure BEFORE failure repeats, Antique appliances, electric motors, fans, ceiling fans, base mount fans, poor equipment performance, Modifications, habitual failures, vibration, redesign, obsolete issues, collectible items restored, rewinding. Owner of EMR Repair Inc www.emrrepair.com More information on electric motors, under Engineering/Motors Ask about any electrical or mechanical problems in the home, office, or even at your work. B2B or business to business CONSULTING I can do but it would be a much more complex issue, that would require a significant amount of time. repair@mearservice.com from there we can discuss and begin work on about anything. Industrial electric motors, controls, troubleshooting, vibration, alignment, any type of industrial or commercial electric/electrcical equipment For the home owner, renter, apartment if you have odd things going on, describe to me, photos are normally very helpful, appliances, heating and air conditioning issues, light switches, installation, DIY PROJECTS FOR THOSE NOT EDUCATED IN ELECTRICAL, we can do some things, but for safety and sanity reasons, I may refer you to a local electrician, and help you find one, help you with pricing and even speak directly with anyone you hire if you have issues,


Over thirty years with a major repair and sales company, VP of Operations, and former owner of my own specialty repair shops, MEAR Services local to Kansas City Missouri EMR Repair Inc., located in Kansas City Missouri, 2014 sold both businesses to JCI Industries, Lee's Summit Missouri wbabbitt@jciind.com Evaluation and repair of electrical/mechanical apparatus. Electrical and mechanical repairs, trouble shooting including, vibration and balance issues. About.com provides this service, and the huge costs to provide help on about any subject. They provide the servers, the people to vet the experts, costs that would be the same as operating a good sized business, They should be appreciated for what they do, the huge costs and the great help they provide for free, Electric motor questions, can be answered here but there is a dedicated category that has other experts to help and add to a solution. Other common questions, are noises in the walls, breakers tripping, devices not starting or shutting down for no apparent reason, smoke alarms buzzing, thermostat change outs, or sizing wire or needing information for a new project, but anything can be resolved, anything, with enough effort and patience, DIY, with electrical is possible, but in most cases the use of a simple ohm meter or volt meter is needed, they can be purchased at any hardware store for a few bucks. If you have smoke, or smell smoke, don't be writing me, call 911 the Fire Department has no problem looking for smoke smells, better then spraying water on a blazing fire. DO NOT GET CAUGHT INVESTIGATING AND TRAPPED IN A BASEMENT LOOKING FOR A BLOWER FAILING< As to the tip jar, it is up to you, it is appreciated, every expert spends out of pocket that I know, we spend on IP time, computer wear, printing documents, books, and of course our time, but if we prevent a $400 service call, we did well,

Former IBEW, EASA, IEEE, UL, ..............


10 plus years, various Technical Schools, followed by Industrial College Credit and non Credit Courses, electronics courses, experience in most any electrical apparatus, electric motors and generators, AC OR DC, fractional to above 5000HP, other electrical apparatus, slip rings, sleeve [plain] bearings, lubrication, identification-no data plate, control components, service and sales. I have continued night schools for decades, the list is extensive. I have been in the business of repairing most anything with wires or mechanical parts for decades, I have some helpful hints and directions you won't have to dig up. Or hopefully not have to pay a huge service call invoice to find.

Awards and Honors

Past/Present Clients
Federal Government, National Weather Service, NOAA, Commercial Power Plants, Major Vehicle Manufacturers, Printers, Other industrial and Commercial Businesses

©2016 About.com. All rights reserved.