Electric motor diagnostic FAQs set #2:

These questions and answers help in diagnosing or repairing electric motors. The page top of an oil burner electric motor points out that many electric motors used on building mechanical systems and appliances look a lot alike.

This article series describes A/C electrical motor troubleshooting: here we provide an electric motor diagnostic table, a troubleshooting guide that helps diagnose and repair most electric motor problems for motors found on HVAC equipment in buildings such as air conditioners, furnace or air handler blower fans, oil burner motors, well pumps, and condensate return pumps.

A/C Electric Motor Troubleshooting FAQs

at left our photo illustrates the motor as typically found in a direct-drive HVAC blower or air handler assembly.

[Click to enlarge any image.]

These questions & answers were posted originally at ELECTRIC MOTOR DIAGNOSTIC GUIDE - home.

On 2017-03-05 9 by (mod) - software to connect sound monitoring to a central computer

The software I've seen was custom coded by engineers.

See for example, NTI Audio/s XL2 Analyzer used for live event sound monitoring.

NTI Audio, NTi Audio Inc. 7405 Tech Center Drive Tigard, OR 97223 USA, Brian MacMillan +1 503 684 7050 XL2 Analyzer dB monitoring hardware and software includes sound level prediction! Retrieved 2017/12/14, original source: http://www.nti-audio.com/en/solutions/live-sound/sound-level-monitoring.aspx

Excerpt: the XL2 measures the correction values between the loudest point of the live event and the actual measurement position, e.g. the front-of-house. These correction values are included with the actual measurement data, thus you have the level at the loudest point in the public area under control.

NTI has offices in the U.S., Europe, and Asia.

On 2017-03-05 by Jeffrey James Hunter

I'm trying to use sound sensors, placed on HVAC equipment, connected to central computer monitoring, to anticipate componant failure. Is there software designed to do this?

On 2017-02-11 18:02:15.564079 by (mod) -

Anon

I wouldn't make that change without checking with the furnace manufacturer.

On 2017-02-11 08:14:32.150145 by Anonymous

Can 1/3 hp furnace blower motor be used in place of 1/2

On 2016-03-03 by (mod) - loud noise when water pump turns on - pump not cutting in

Norris

Set the pressure tank pre-charge to 2 psi below the pump cut-in pressure setting.

I can't guess at the noise you cite - look more closely onsite for loose pump mounts, failing pump bearings, burning switch contacats, water hammer.

On 2016-03-02 by Norris

My water pump meter shows 0 percent, I put air pressure in the tank to 25PSI,the pump still pumps water into the house and while doing so this loud noise come from ether the switch or the motor I do not know for sure, any ideas?

On 2016-02-09 by (mod) -

Thomas

I looked at your photos: it looks to me as if there is a leak in the boiler. I'm not certain but a closer inspection is warranted. ...

Sorry Thomas, our system blocks links or text that it thinks are links - to avoid possible malware infection of the website. You can send a link to me directly for checking using the page bottom CONTACT link to find my email.

See HEATING SYSTEM NOISES

On 2016-01-17 by Thomas

I have a guy coming early this week. I poked my camera into the boiler to try to photograph inside. I put a link to my Flickr acct here . So if anyone can tell if this is a normal looking interior or not let me know . I`ll update soon. Regards

On 2016-01-14 y Anonymous

I`ll try that soon . Thanks for the information!I might have to get somebody here to take it apart if I don`t see anything inside. Thomas

On 2016-01-14 by (mod) -

Good comments, Anonymous. I would look inside of the combustion chamber with the burner switched off of course with a flashlight.

You may see mineral deposits or stains that will be a clue shown you the water has been leaking into the boiler interior. If all of the coatings and colors in the combustion chamber are uniform then there's probably no leak there. In that case you can also look for a leak on the boiler exterior by removing its covering jackets. Keep us posted.

On 2016-01-14 by Anonymous

I spoke to a guy that has been in the industry for 30+ years and he said he`s only heard this a few times with Weil Mclain furnaces(although he dosen`t work on them now).

There is a rubber gasket between the pieces of boiler that can deteriorate. This lets some pressure and water out creating a ghost noise.

Another thing was a piece of sand from the casting beaks off creating a hole or cavity.

He said it is very hard to diagnose and possibly you can see some steam or vapor coming out of the chimmney.He said the factory rep has come out and found this a few times. No idea if this is possible ,or true. Not sure if we`ll let this continue or call another service.Installer is not readily available yet.Hired by the building contractor and left very little paperwork. Any comments?

It is forced hot water. I thought air also. System was drained and refilled 1 year ago by the same guy. I have another person coming to look soon.

The circulator and zone valves don`t seem to be making noise by listening very closely or touch.At least its no obvious. There is some kind of air release valve on the piping.
I`ll update this if I find out anything

On 2016-01-12 by (mod) - Weil McLain Model P-W60-4 Series 3 oil burner making a muted horn like noise

It seems we are talking about a forced hot water system. I would start by listening carefully to separate oil burner operation from hot wateen circulation. I suspect the noise is related to a circulator, zone valve, or air in the piping

See HEATING SYSTEM NOISES

Also see this ALPHABETICAL LIST OF NOISES by SOURCE or SOUND TYPE

On 2016-01-12 by Thomas

Hi
I have a WM Gold Model P-W60-4 Series 3 oil burner. Installed about 2005 by a contractor when adding an addition. Only problems were mostly due to ,clogs tanks being from 1957.Its had regular servicing by local companies.
Recently, about 2 weeks now when our burner goes on, after a few minutes we get a muted horn like noise coming through the house loud enough to be noticed as not normal. Sometimes changing in pitch. At the furnace you couldn`t hear it then .

But above it and in even the farthest room from it you can hear it I suppose transmitting through the radiators?

When it stops running the noise stopped.Seems to run fine and works.
Anyway on 1/ 9 I had the regular serviceman come and he cleaned it, changed the filters, changed the nozzle(12570B) , and the cartridge filter on the tanks.

Everything seemed good, no excessive dirt on filters, but he said as he undid the cartridge on the tank it seemed like pressure escaped?Flow was good from tank to unit at filter. Turned it back on and now the noise was heard near the unit plus upstairs. It even remained some seconds after the unit was shut off. He then changed the blower unit.

No change.

Do you have any ideas on what might be causing this?Or previous cases of this happening? He said it might be expansion noise or the boiler or control. But basically he was stumped. I was told to make sure the gauge didn`t go over 180, and to try asking WM support. We are concerned this might be a precursor warning to a part failing, but everthing seems to be working.Any ideas? Thanks.
Regards Thomas

On 2016-01-05 14:34:03.698149 by (mod) -

First step: decide if the problem is an oil burner flame problem, noise of gases passing through a partly-obstructed chimney, or an oil burner motor noise such as a failing bearing;

A mechanic's stethoscope or a good ear at the oil burner should be able to ID the third of these.

Sometimes a vibrating or noisy oil burner transmits noise through oil piping to building framing or floors too. But it would be odd to hear that upstairs but nowhere lower in the structure.

When he shows up, I will be quite interested in what the service tech diagnoses as cause the noise you describe - in some cases it could be presaging a loss of heat.

On 2016-01-04 by Anonymous

Thanks for the reply .I have looked outside for smoke from the chimmney while it is running, not expecting fire but white or black smoke, but not seeing any. The noise does start and stop with the unit. Its been going on for a few days. System was bled last year, by a technician. No smell, smoke,leaks,obvious vibrations or noises in the furnace area. There are smoke detectors too. I`ll have it cleaned Sat , the cartridge filter off the 2 1957 250 gal tanks is in green also.

On 2016-01-04 by (mod) - If the oil burner is smoky, puffing smoke or soot into the boiler room or if you see dense smoke at the chimney top shut the system off

I would check immediately to be triple sure there is no chimney fire. If in doubt call your emergncy services.

If you are certain that the noise comes and goes with the burner cycling on and off, and that it is stopped completely with the burner off, I'm less nervous but the system may still need service or repair.

If the oil burner is smoky, puffing smoke or soot into the boiler room or if you see dense smoke at the chimney top shut the system off and if the smoke doesn't stop immediately get out of the house and call for help.

If none of these safety issues seem present you may be able to wait for repair, figuring we're talking about a failing bearing or even pipe noise being transmitted via the piping to upstairs.

On 2016-01-04 by Thomas - oil burner medium tone horn,not a shriek or whine.

We have a 2004 installed Weil Mclain Gold Oil Burner. Recently its making a noise almost like an medium tone horn,not a shriek or whine.

Only heard in the house upstairs! Not next to the unit. You can hear it in the wall above the furnace placing your ear on it and even in a bedroom farthest from it.

The pitch changes and it starts and stops with the burner??Called a repair guy but he`s not coming for a week?Seems to be working fine otherwise. Should I call someone else for immediate service? Thanks guys.

On 2015-12-26 by (mod) -

Jim: a high pitched sound may be a failing bearing. If so you could be out of heat any time now.

On 2015-12-26 by (mod) - If the noise is from vibration transmitted by the pump then securing the oil line may help

Jim,

If the noise is from vibration transmitted by the pump then securing the oil line may help; If it's not a vibration but an actual pump bearing failure then you'll probably need to replace the pump;l

There is a replaceable filter screen in the pump for which a replacement screen and gasket kit are available.

See FUEL UNIT, HEATING OIL PUMPS where we discuss noises and vibration transmission through oil piping

On 2015-12-26 by Jim Schubert - oise coming from fuel oil line to fuel oil pump

Located noise coming from fuel oil line to fuel oil pump. Is pump bad are do I just need to clean the filter?

...

Oil burner makes a high pitch sound when running.

On 2015-09-29 by Peter

Thank you, apologies on my lateness, I only just viewed the site again now, end of September! I'll check out your suggestions. Best wishes!

On 2014-10-27 by Connie

Can you give me info on a Becket Burner Sound Cover for AFG series burner.

Need to minimize boiler sound in room above boiler. Thinking about insulating cellar ceiling (now has fiberglass insulation) with Roxul, but thought I might try this cover first.

I guess that I am wondering if anything actually works. I am sick of guests always saying "what's that" when boiler starts. Heating unit seems to work fine, and is only 10-yrs. old.

On 2017-11-29 by (mod) -

Repair vs replace DeWalt chop saw motor

Sounds like the motor is overheating just as you say. Often the rotating shaft or shaft bearing overheats and binds. Or internal windings become worn and damaged.
The table above gives some motor diagnostics that in turn would direct the repair.

You might undertake a repair as a fun project (do not get electrocuted, right?) though often it is economical to just buy and install a replacement motor.

Before replaacing the motor, check and replace the motor brushes. If the motor sparks like mad I suspect bad brushes.

You can buy a DeWalt motor armature fdor between $70. and about $95. U.S. - the part most likely to have worn out in a hot motor.

The DeWalt motor field assembly (the motor's outer shell) is discontinued for some models but will probably be simiar in cost. Look for parts for your DeWalt chop saw by using the model number in your search.

On 2017-11-28 by Danny

I have a Dewalt chop saw that I bought used for a very low price. It runs but as I suspected, after one or two cuts the motor loses power, over heats, and emits that all too familiar, burned out electric motor smell. I am not greatly experienced in electric motor diagnostics but would like to know what exactly has happened to this unit, and how to go about repairing it.

On 2017-11-23 by (mod) -

electric motor in a Toro Weedeater

Frank,

The electric motor in a Toro Weedeater is indeed not one intended to be lubricated, nor was it designed for easy consumer repair or replacement.

In general when a small torque-driven electric motor like that in your Toro Weedeater slows down, it's because the

motor's coils are worn out,

the motor is overheating,

its rotating shaft is binding.

But another possibility is that a motor run capacitor has failed. The capacitor, by storing electrical energy momentarily, keeps the motor spinning through its electromagnetic field.

Someone familiar with basic electrical repairs and use of a soldering iron could try (WITH POWER DISCONNECTED to AVOID FATAL SHOCK) removing the motor (open the Weedeater, clip the soldered ends of the pair of black and pair of white wires, and pull the motor).

With the motor removed, if its drive shaft can be rotated by hand then the motor is not quite bound up. You could take the motor apart, find the capacitor, a cylindrical electrical device soldered to one end of the coil, and replace it.

Or you could just order a whole new motor from Toro. However when I searched for replacement motors for the electric Toro weedeater I did not find the motor available - if your Toro Weedeater is 5 years old or older you may not be able to find a replacement motor - it's time for a new WeedEater.

On 2017-11-23 by Frank Wendling

I have an electric Toro weedeater. When I start using it the motor appears to run at normal speed but over a period of 3-5 minutes the motor slows down and eventually stops. I removed the motor to see if I could find the problem.

The motor is riveted together as opposed to being put together with bolts, so taking it apart to check/clean/replace the bearings doesn't appear to be an option.

I did remove and check the brushes, which looked fine to me. Although I probably can't fix the motor, I would really like to know what causes the motor to slow down and stop. Your thoughts and expertise would be greatly appreciated.

On 2017-10-16 by Pete

After rebuilding an old table saw the motor started smoking after running for about 3 minutes. There was a bunch of saw dust in the windings so I blew out what was left. I noticed there are blackened wires on the inside of the motor. Is it still safe to use?

On 2017-09-15 by brad

dog ate through cord on treadmill. replaced cord now when I turn on treadmill it trips the 10 amp breaker. any ideas

On 2017-09-14 by (mod) -

A 3-phase motor for a steel cutter

Jeff:

If you are sure that the motor, its control switch, and the actual cutter mechanism were working fine before and that the machine wasn't flooded or otherwise damaged, I suspect that its current draw is higher than the generator provides, OR that the generator is only supplying 2 phase power.

Let me know.

On 2017-09-14 by Jeff

A 3-phase motor for a steel cutter ,once wsitched on ,the RCD trips from the main Braker .The power source is from the Generator,what could cause this?

On 2017-09-03 by Cherhl

Blower fan on attic is having g trouble coming on to run air-conditioning.

On 2017-08-28 by (mod) -

hedge trimmer motor repair

Probably, Traci, but first you want to know just what is damaged since the repair cost might be too close to repalcement cost.

If the motor doesn't run because the trimmer blades are mechanically-jammed it should be possible to disassemble the blades, straighten the parts, perhaps filing smooth the damaged area - though you may find that the blades no longer cut well in that area. If the motor seized and burned-up, then even after freeing the blades it won't run and it is not safe.

On 2017-08-28 by Traci

If hedge trimmer motor doesn't run after hitting small rod-like piece of metal, can it be repaired? Please send info to scott.traciscott.traci@gmail.com.

On 2017-08-27 by (mod) -

the mouse ate my 7.5 Hp single phase electric motor

Sounds like a very satisfying success story, Andrew, and encouraging that you also are taking steps to keep the mice out lest they simply make trouble all over again.

If you have any details to add (or photos) about where you found trouble in the motor and what had to be fixed, that'd help other readers.

Daniel

On 2017-08-27 by Andrew

Neighbour came over and helped me out . Done a couple things wrong and we got in running again. Closed up all the places the mice were getting in to prevent it happening again. Nice page though very good stuff.

I had a mouse get into my 7.5 Hp single phase electric motor in the front of the motor. Motor was running my Farm King roller mill. The mouse got through in the wiring. When I started the motor it would run real slow and eventually trip out the breaker.

I removed the front cover and found the dead mice and put everything back together but now the motor shaft would not turn freely without using a pipe wrench and the motor doesn't even hum when I apply electricity to it. Is it possible that I may have missed something when putting everything back together that could have lead to this problem.

I smell no burnt wires or anything and this motor is only used an hour every few days could it have failed so easily?

On 2017-08-26 by (mod) -

bad control relay on a motor

Hussein,

Since the windings, bearings, stator and other internal parts of an electric motor are used equally in either rotational direction, if a motor is not working properly at both speeds at its high speed I suspect a bad control relay.

But there is another subtle possibility - I am speculating here. When the motor winding wire is damaged it might open at high speed in one rotational direction but not in another, simply because of the physical location of the damage and the direction in which the winding wires are wrapped. In one direction rotation may force a loose wire connection to be more tight while in the opposite direction the wire may tend to open.

This is difficult to detect by normal motor tests when the motor is on the test bench and not actually spinning.

On 2017-08-26 by Hussein

double coil 380c electromotor for elevator fast speed only works in one direction , slow speed works fine im both directions.
what might be the problem?

On 2017-07-19 by (mod) -

motor not getting elecrical power

Sounds like it's not getting power

On 2017-07-19 by Watson

I have an air compressor I've ran 220 to it, I have tested and have power to it but the motor does nothing. I've taken the motor off and to a local electric motor shop he hooked it up and it worked fine. I brought back home hooked it up and again nothing. I then bypassed the on off switch on the compressor and hooked the wires up direct and still nothing at all no humming noises or anything.

On 2017-07-07 by DAN

I have a small 2.5hp compressor thats had about 4 hours use over the past 5 years, its now developed a problem with the motor. The rotor is attached to the shaft by a very fine thread along its length untill it comes to a stop at the end of the shaft

. The rotor is now undoing on the shaft until it hits the back of the motor casing and trips the fusebox in my house. Is it possible that a electrical fault could make the motor run backwards causing this or any other ideas, thanks

On 2017-06-27 by JW

Hi, I have a fairly new pitching machine that uses two wheels (2 motors (AC motors I think since it plugs into an outlet)) - one of the motors runs slower and makes a clicking sound. How can I find someone who repairs AC motors in my area?
JW

On 2017-06-27 by Chris

three ton grand air unit, rained really hard. condensor motor not running and very hot. cooled it off with the hose. motor ran for a short time and shot up a stream of smoke or steam, no smell. Is the motor shot

On 2017-06-23 by prasad kadali

what would be the problem if current is passing into table fan motor but the rotor is not rotating

On 2017-06-14 by (mod) -

right motor capacitor vs other problems

If you are sure capacitor is the correct type and rating, then I would look further for low voltage or a loose or corroded electrical connection, or a failed motor bearing that is binding the driveshaft

On 2017-06-14 by Keith

Hi I have a Sequence pond pump? And last time cleaned the filter, when switched it back on, the motor started humming so spun the the fan and the motor started running ok. Then the other day cleaned filter again motor runs slow?

Was told it was capacitor so changed it to the spec that I could hardly read but still runs slow and gets hot?
Any ideas? Thanks

On 2017-05-31 by JW

Hi, I have a fairly new pitching machine that uses two wheels (2 motors (AC motors I think since it plugs into an outlet)) - one of the motors runs slower and makes a clicking sound. I think I could fix it myself with instructions. Thanks.
JW

On 2017-05-09 by (mod) -

take the electric motor to a testing service

Kevin you may need to take the motor to a testing service; typically the tech looks at the current draw and compares that with the motor nameplate data, then looks for a winding that opens when the motor spins. An A/C tech typically starts by swapping in a start/run capacitor.

On 2017-05-09 by Kevin

How can I tell if an AC 15 horsepower motor is bad. Can I turn it by hand with easze

On 2017-04-28 by (mod) -

Irfan

I would take the motor off and to a test service or test bench; you need to know if the problem is

- low voltage to the motor

- a bad start/run capacitor

- a damaged motor winding

- worn out motor brushes

- a worn out or seizing bearing

- something else

Some of these parts can be replaced; usually for a washing machine motor rebuilding wouldn't be economical; you'd replace the motor.

Look for washer leaks into the motor. (UNSFAFE)

TURN OFF ELECTRICAL POWER to avoid being killed.

On 2017-04-27 by Irfan Joeya

My washing machine's starter motor have lowe output power and overheat pleas guide me that what's are the causes and what is remedy for this fault?

On 2017-04-23 by (mod) -

signs of a bad motor start run capacitor

That suggests that the motor has a bad start-run capacitor OR a bad electrical connection or control switch.

A conventional circuit breaker wouldn't know how to send different voltages to different things connected to it.

On 2017-04-23 by Anonymous

Thanks very much for your quick response. I have had the motor with the impeller out and everything spins very smoothly by hand.

This motor shares a quad circuit breaker with a slightly smaller motor used for the spa booster pump, is it also possible that the breaker is failing to send the right voltage,only to one,circuit or does everythng points to a failing capacitor? Thanls

On 2017-04-23 by (mod) - signs that a pump motor needs a new start or run capacitor

That suggests that the motor has a bad start-run capacitor OR a bad electrical connection or control switch.

A conventional circuit breaker wouldn't know how to send different voltages to different things connected to it.

On 2017-04-23 by Anthony

Thanks very much for your quick response. I have had the motor with the impeller out and everything spins very smoothly by hand. This motor shares a quad circuit breaker with a slightly smaller motor used for the spa booster pump, is it also possible that the breaker is failing to send the right voltage,only to one,circuit or does everythng points to a failing capacitor? Thanls

On 2017-04-23 by (mod) - repair a water pump that can't start

Anthony

That sounds like a motor or pump impeller that's seizing - you could try a start/run capacitor replacement but first see if the pump motor and impeller will spin freely so you don't waste time on the capacitor.

Once a pump starts, even with a bad bearing, it may keep running but when it stops the combination of heat, lost lubricant, or bad bearing will make it hard to re-start - or as you say, maybe we're lucky and it's a bad capacitor.

On 2017-04-22 by Anthony

My waterfall pump motor will only start after 4-5 attempts. It hums the frst 4-5 times amd will then start And run very smoothly fror hours ! the shaft rotates freely. Could it be the capacitor?

On 2017-03-23 by (mod) re: compressor motor sparking badly

BR

You should turn off the compressor unit power right now to avoid a possible electrical fire or shock.

There are companies who re-build electric motors, or IF (which I now doubt) your motor has not been actually damaged by the remains of the brushes that wore out, you may be able to take the motor or remains of its brushes to an electrical supplier to find a matched replacement. If not you'll need to contact the manufacutrer of the motor with the data on the motor's data tag.

On 2017-03-23 by B_Rad

My compressed motor is sparking bad at the contact of the brushes how can I fix this they get red hot and start smokin

On 2017-03-17 by (mod) re: clicking at control relays when a motor doesn't run

Click is probably a relay closing;

I can't guess if the problem is a control board, or the fan motor is shot or there's a bad fan motor start/run capacitor.

If you never heard the fan motor humming and it was never hot (what you never listened to the hummer?) then some testing of the motor is in order. Often if the tech doesn't see an obvious burned or shot component she will just change out the capacitor as a cheap thing to try.

On 2017-03-17 by Tim

I got a problem I need some help on please. I when I turn on my a/c inside the house, everything inside turns on fine but the fan outside will not. All I get is a click (outside). Does that mean that the fan motor is blown?

On 2017-03-03 by (mod) re: signs of a seizing electric motor

Sounds like a seizing motor - that'll draw high current and trip breakers. Could be a bad bearing or if the motor spins freely then I'd expect a motor expert to look for a shorted winding. The amateur quick and dirty test is to replace the start/run cap if the motor uses one.

On 2017-03-03 by Anonymous

Last update. Took the switch assembly off the saw and before testing it decided run motor one more time while on the bench. Well, when I plugged it in it tripped the circuit breaker. Turned off all the lights in the shop and plugged the motor in again. This time the circuit breaker did not trip but the motor only hummed. So, problem appears to be the motor.

Any ideas what the issue with the motor might be? I would sure like to solve the problem myself if I can.

On 2017-03-03 by (mod) re: Sears table saw motor repair

Possibly though that's not so common. It could be the motor can't start when under load. I would reinstall the motor in the saw, assemble everything as before, but then bypass the on-off switch temporarily to see what happens. Let me know.

DO NOT cut off any fingers.

On 2017-03-03 by Anonymous

Update on the Sears table saw. Took motor off the saw. Placed on bench and plugged directly into outlet. Motor ran fine. Again, the blade and corresponding pulley/shaft turns freely. The motor has a three prong line that plugs into on/off switch. Switch seems to be the culprit.

Can a faulty switch provide line voltage but insufficient amount (110v) to propel the motor thus causing the hum?
I have a Sears table saw that is probably at least 40 years old. Never had a problem until today. When I turn on the switch all I get is a hum. The blade turns easily by hand as does the motor shaft Any ideas?

On 2017-01-29 by Doug Ingram

Just to add one more possibility. Heater blower suddenly stopped working. Turns out the set screw on the pully had gradually loosened over the years and became disengaged with the electric motor shaft. The motor at first appeared to be defective but upon inspection, the shaft was found to be turning properly with power. Solution: Reset the set screw and tightened it up sufficiently. Result: Working better than ever.

On 2017-01-23 by Anonymous

@Rod, it is an 5 hp 120 volt
My motor turn go but if I hold the shaft it don't turn what cause this it off or my. Air compessor

On 2017-01-18 by mike

I have a small saw with a small motor. The motor will run but only if I rotate the armature a little bit. Then it will run. If I stop it ( turn it off with the switch) it will not restart unless I move the armature about one half an inch again. What' might be wrong? the switch is new and works fine.

On 2016-12-23 by (mod) re: industrial coffee grinder motor runs at half speed

Jim:

Is this a 240V motor? Some 240 or even 3 phase electric motors will still run, but poorly, if they're missing voltage on one of their supply wires.

Some electric motors also have internal jumper connections that will by design run the motor at different speeds.

Take a look at the data tag on your motor for its specifications.

Check also for low voltage to the motor

Use the page top or bottom CONTACT link to send me some photos.

On 2016-12-23 by Jim

I have an electric industrial coffee grinder. It is 1/2hp. I let it get too hot one day and took it to be redone. It came bach running at about half speed. Not enough RPM to throw the ground coffee out. Ideas please ?

On 2016-12-17 by orlin

I need a wireing diaghram for putting new start capactors in a 7.5 motor, this motor does not have ruhning cAPACTORS

On 2016-12-10 by (mod) re: turn OFF smoking electrical equipment right away

TURN OFF the equipment immediately and leave it off, Anon. It's unsafe. If smoke continues or increases after turning off the smoking motor, go outside and from a safe location call your fire department.

On 2016-12-09 by Anonymous

When motor starts to run it started to smoke

On 2016-11-28 by Ed barberry

I recently moved into a house that has a electric motor to draw water from a pond to water the lawn, i was told it hasn't run in over 10 years and of course it won't turn on and any suggestions how to get it going or fix it
Thank you

On 2016-11-28 by Roeks

My house fan motor runs slow. Setting one runs not at all, 2 struggles 3 and 4 runs very slow and I must help the motor to run by hand when switch on.

On 2016-11-27 by Anonymous

I came to work and the spa motor wasn't working so I thought that water had got to the wires cuz the capacitor sits on top of the motor and has exposed wire so I used compressor to blow out the wires and then I gave it power and sparks flew I quickly shut it off and now there is no power even going to it. Can someone plz help me figure this thank you.

On 2016-11-23 by oo

what if my motor does not run .... what is the cause and the solution

On 2016-11-08 81 by (mod)

Don at BIN95
Thanks for the suggestion about the motor troubleshooting article - we've added links to it in the

article ELECTRIC MOTOR DIAGNOSTIC GUIDE

...

Continue reading  at ELECTRIC MOTOR DIAGNOSTIC GUIDE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Electric Motor Diagnosis & Repair Articles

• ELECTRIC MOTOR DIAGNOSTIC GUIDE - home
  • A/C ELECTRIC MOTOR COMPONENTS
  • BURNED-OUT COMPRESSOR
  • CAPACITOR TYPES, for MOTORS
  • CAPACITORS for HARD STARTING MOTORS
  • CHATTERING RELAY CONTROL SWITCHES
  • COPELAND ELECTRICAL HANDBOOK [PDF]
  • ELECTRIC MOTOR 3-PHASE MOTOR SELECTION
  • ELECTRIC MOTOR 3-PHASE TROUBLESHOOTING
  • ELECTRIC MOTOR CENTRIFUGAL SWITCH or PTC PRD
  • ELECTRIC MOTOR DATA TAG
  • ELECTRIC MOTOR HORSEPOWER & CIRCUIT WIRE SIZE
  • ELECTRIC MOTOR LUBRICATION
  • ELECTRIC MOTOR NOISE DIAGNOSIS
  • ELECTRIC MOTOR OFF on RESET
  • ELECTRIC MOTOR OVERHEATS
  • ELECTRIC MOTOR OVERLOAD RESET SWITCH
  • ELECTRIC MOTOR RUN DIRECTION
  • ELECTRIC MOTOR START SWITCH
  • ELECTRIC MOTOR TESTS
  • ELECTRIC MOTOR WIRING DIAGRAMS & GUIDES
  • ELECTRIC MOTOR WON'T START / RUN
  • HARD STARTING COMPRESSOR MOTORS
  • HARD STARTING ELECTRIC MOTOR CAUSES
  • OIL BURNER NOISE DIAGNOSTIC INDEX
  • RESET BUTTON, ELECTRIC MOTOR
  • TIGHT or SEIZED AC COMPRESSORS
  • WATER PUMP PROTECTION SWITCH

Suggested citation for this web page

ELECTRIC MOTOR DIAGNOSTIC FAQs-2 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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