Instructables

Electric Mower will not start, trips the breaker?

I have a Task Force model #25143 electric mower (corded) that suddenly stopped while I was cutting some grass that I admit was probably too tall.  I have had no previous problems with it whatsoever since I bought it new last year.  After some searching I found out that it had tripped the breaker (was plugged into the GFI outside the house).  It's only a short cord--an extension must be used.  I bought a new one last month, but tried two other ones just to be sure--no change.  I tried using a different outlet--no change.  I tried using an inside outlet and promptly tripped that breaker as well.  I checked the blade, it spins freely, there was a small amount of grass on the shaft above it, I removed that.  There was a lot of cut grass on the underside of the deck (it's a mulching mower) and I removed all that going to the side discharge and the chute where the bag would be.  I took off the cover to the motor, there was some grass and dust in there, I cleaned it all out.  As for the connections, they are still clean as a whistle--no rust, corrosion, burning, fraying, etc. they still look new.  I was looking for a fuse and couldn't find one, checked by the motor and in the handle where the switch is.  After all this it still trips the breaker so I'm thinking there has got to be a short. The plug side of the extension cord was warm.  I found an answer that said use a multi-meter and I suppose I could go buy one but then what do I do with it?  I don't know what I'm supposed to hook it to and I don't know what any of the readings would mean.  I'm too low on cash now to pay for repair or buy a new one and where I live the grass needs to be cut almost 2x a week--any advice?  How can I find the short or is the motor gone?  I also read about motor "brushes" but don't think I saw any not that I would know what they look like anyway.  I included pics of the switch and the motor.

Picture of Electric Mower will not start, trips the breaker?
IMG_0077.JPG
breichard1 year ago
PurpleMom could you please explain to me what you did to get this fixed exactly? Which bridge capacitor did you buy? How did you install it and where? I'm guessing it's on the handle control unit. Did you take that black-gray box apart with all the wires going into it? Or did you buy a new one of those? If you took it apart does the bridge capacitor/rectifier just come unplugged? Then you plug a new one in?

My mower is doing the exact same thing as yours so it would be great if I could get a few more details from you to fix mine. THANK YOU!!!!
PurpleMom (author)  breichard1 year ago
I don't remember where I ordered the part from, but I'm including 2 new pics--1 of the part itself and 1 of the location in the mower. It's on the deck next to the motor, and all those wires plug onto the terminals sticking up from it. I took my part off (it's only held on by a single Phillips head screw through the center) and studied it. Then I did a web search for "KBPC2504" which was marked on my part. Bingo! Lots of things came up, with pics that looked just like mine. I browsed some and chose a site that had images and measurements, compared those to mine, and ordered 2 since they were only about $2 each. Figured I could risk less than 10 bucks. Shipping charge was small. Worked like a charm and I have a spare just in case it were to happen again. Hope this at least gives you a starting point, I know lots of things could be wrong, but sometimes the answer is really simple and just takes some trial and error. I still don't own a voltmeter! :-P Sometimes you just get lucky, though you wouldn't think it to look at the rest of my life!
IMG_20130819_212215.jpgpart.png

I don't know if anybody is still following these comments, but I wanted to shout out a HUGE "thank you" for your photos and information. I had the same problem with a different brand (Greenworks) electric mower and decided to buy the bridge rectifier (which is the identical part that you posted here) and it worked like a charm! You saved me tons of money!!

You are awesome! I actually took both the handle and the motor area apart yesterday after I posted to you and immediately saw the bridge rectifier in the engine area. I did the exact same thing you did. Took pics and ordered the part after a google search. I was going to post them today for others but you beat me to it! Hopefully this thread well help out others as well. My lawn mower is doing the exact same thing as yours, so I'm pretty sure this will fix it as well. If not I'll post more later. Thanks again!
I just wanted to give an update on this. This worked on my mower as well. Although I ordered a different part as I saw from below that it might be better to get a slightly higher amp bridge rectifier so it won't burn out as fast. It was super easy to fix and install like PurpleMom has stated. In case you need a link to the part I ordered its -
http://www.digikey.com/product-search/en?lang=en&site=us&KeyWords=GBPC1504DI-ND&x=0&y=0

Just under $3 and got it running like a new mower again. The original part is rated at 12.5 amps, the one I ordered is at 15 amps.
Should add it's part # GBPC1504DI-ND in case that link doesn't work.
iceng2 years ago
Where does the blue wire Go ?

Trying to make a schematic of this contraption.

A
zaronas iceng2 years ago
well id say it goes in to the bundle of wires but other than that i have no idea, it looks like it probably is the opposite of the yellow wire so find the yellow to find the blue
zaronas zaronas2 years ago
it could be a ground wire but i doubt that
iceng zaronas2 years ago
Thanks to the good (author) photo the blue joins the green
on the DC bridge.. -.-. . -. --.
zaronas iceng2 years ago
hmmm cool
iceng zaronas2 years ago
Final  Circuit  Wiring.
This includes a resistor to limit current through the switch when
stopping the blade inertia as a dynamic brake. 

If you can lift the blue wire from the brush and switch the power on.
A shorted bridge will trip the breaker.. -.-. . -. --.
mower-motor.JPG
iceng iceng1 year ago
Read this again
PurpleMom (author)  iceng2 years ago
YES! This is 100% what happened too! I am looking for a replacement for mine they don't seem to be very expensive in general.
iceng PurpleMom2 years ago
Thanks for the conformation :)

Those DC bridges are not supposed to ever fail,
unless a cheep design engineer put a low current bridge in your mower.

And when you started cut the high grass,
that extra load did damage to the DC bridge.

A.. -.-. . -. --.
Instead of blowing house breakers, my Task Force 25113 just stopped working when I hit the "high grass". There was a circuit breaker with a translucent flexible cover on the right handle bar on the inside of the black plastic housing that the power cord passes through. I just pushed the black plastic button of the breaker-switch by pressing on its translucent flexible cover that I previously referred to and my mower came back to life. :)
I have an Earthwise mower with nearly identical setup, based on the pictures. Mine trips the breaker as soon as I plug it in. It doesn't even wait for me to pull the activation lever. Would this be the same issue, or is my problem in the switch itself?
PurpleMom (author) 2 years ago
A HUGE THANK YOU TO ALL OF YOU FOR HELPING OUT! It started up first try after installing the new Bridge capacitor, which only took about 2 minutes. I appreciate your patience and the effort you gave. Now my only excuse will be "it's just too hot to mow the lawn right now!" Thanks again.
I am guessing that your electric mower is wired in a way that is similar to the wiring in this picture,
http://www.tehhouse.us/electrical/lawn_mower/bandd/mower_wiring_diagram.png
from that page I linked to yesterday,
http://www.tehhouse.us/electrical/lawn_mower/bandd/index.php

There are only so many things that could go wrong here.

My intuition is telling me that it is probably the bridge rectifier (the little 4 terminal black brick there). Guessing that it failed in such a way that it sort of turned into a short.

Supposing the bridge rectifier is capable of tripping the breaker all by itself; i.e. if you unplug the red+yellow connector from the (+) terminal of the bridge rectifier, and unplug the green+blue connector from th (-) terminal of the bridge rectifier, then that will leave just the white and black wires, which get connected to the (120V?) mains power when you turn the switch on.  Anyway if that little black box can trip your breaker all by itself, then that's probably where your short is.

But it is kind of crude, to keep using your breaker as your test equipment.

I know you said you did not know how to use a multimeter, but this is kind of a strange sentiment to hear from someone who wants to fix something electrical.  It's sort of like saying you want an omelet, but you don't really know how eggs work. I mean, what do you do? Find someone who does understand eggs, to make the omelet for you? Maybe.

Zaronas mentioned cheap voltmeters, and a retail chain in the Former US called HarborFreight(r), e.g:
http://www.harborfreight.com/7-function-digital-multimeter-92020.html
It turns out that I like their voltmeters too. Mostly because they're cheap, and that way I don't feel too bad when I accidentally break one.

Now the part where I teach you how to use a voltmeter... Ha! ;-)

Well, I mean it's not that hard, unless you have to explain to someone else how to do it. Explaining it is hard!

Anyway, in the context of examining a bridge rectifier, like the person in this video is doing,
How To Test A Bridge Rectifier With A Digital Multimeter DMM
http://www.youtube.com/watch?v=dqkT6hF0O3E

Basically what is happening is that he is examining the individual diodes in the bridge.  Diodes only conduct in one direction, so that is sort of what is going on with the action of swapping the probes and trying the measurement again. If you find a diode in the bridge that is conducting in both directions that's bad news.  It means one of the diodes has turned into a short, and the whole bridge needs to be replaced.

If your meter has a diode-test setting, it should be switched to that setting when testing diodes.  Sorry if any of this seems obvious.
PurpleMom (author)  Jack A Lopez2 years ago
Well, I don't know how to use a multimeter because I have never had one. Maybe it's easy, I also can't drive a stick shift but I might be able to do that too. I don't WANT to know how to fix electronics, I just have no budget to do anything but fix everything myself no matter what it is. I had to change out the run capacitor on my house's AC, and I had a burnt contact--I stripped the wire and crimped a new contact on there and now it's going great. I didn't want to do that either, but I had no choice it's 90 with 80% humidity and I'm poor. I have no clue what that wire does, but it works now. So, until someone wants to come to my house and fix everything for free or I win the lottery it will be like this. I just have to keep learning. If I have to learn about diodes, resistors, and capacitors, I will--but for right now I just need to mow my lawn before I get fined. :-P There is a HF Tools near here and I have a semi-free day Thursday I will try to get one. PS...my omelets are fantastic and I even crack the eggs myself, and my theory is the chicken came first.
You'll have to forgive Zaronas and I for evangelizing, for trying to draw you into the temple of the multimeter.  But this is our culture, and people outside this culture seem strange and primitive to us. 

For example, anthropoligists like to tell stories,
http://numberwarrior.wordpress.com/2010/07/30/is-one-two-many-a-myth/
of primitive societies they've discovered, who have no words for, and no concept of, numbers greater than about two. The usual way the story is told is that their entire number system consists of, "one", "two", and "many". Any number greater than two is just "a lot", or "many". For such a people, more abstract mathematical concepts like, addition, multiplication, or even compound interest, would be so abstract as to be incomprehensible.

You might wonder at these people, wonder how they could get by without being able to calculate the interest on their bank accounts, or the gas mileage their SUVs are getting, but somehow they do.

And somehow you managed to fix your air conditioner, without the aid of a multimeter. I am impressed by this.  Also for your electric lawnmower, it is starting to look like it is definitely that bridge rectifier. That too, it seems you have figured out, without using a multimeter. At this point a multimeter would serve only to confirm the bridge rectifier is broken, and you might wonder at the value of that.

Nonetheless, I claim a multimeter is a useful tool to have around, and you will probably find uses for it in the future, if you continue to follow the path of learning about electricity,
http://www.allaboutcircuits.com/
and if the electric things you own keep breaking, and that's pretty much a certainty based on the perverse philosophy, of  "planned obsolescence", of the people who manufacture these things.
http://www.youtube.com/watch?v=jooYHPrgvFs

I don't know how fast your grass grows, but probably the next move in this game is going to be to find a new bridge rectifier.  Offhand I cannot think of any brick-and-mortar type stores that would have this part. I think the author of,
http://www.tehhouse.us/electrical/lawn_mower/bandd/index.php#rec
suggested Digikey (http://www.digikey.com) and that's probably as good a place as any.
I think the parameters you're going to want are: peak inverse voltage greater than 300V, forward average current greater than about 25 A, and a size and shape that will fit neatly in the space where the old one was, also with its four little blade connectors
http://en.wikipedia.org/wiki/Electrical_connector#Blade_connector
 the same size as before.  That way you can just slip the old connectors onto it.
This kind of looked like a good one:
http://www.digikey.com/product-detail/en/GBPC3506-G/641-1378-ND/2074843
The data sheet
http://www.comchiptech.com/cms/UserFiles/GBPC15005-G%20Thru366543.%20GBPC5010-G%20Series%20RevA.pdf
said its little blade connectors were about 0.25 inches in width, and I am guessing that is the same size as your connectors, just from looking at the picture you upped.  Be sure to actually measure the width of those connectors yourself, just to make sure the replacement will fit. 

BTW, one sort of annoying thing about these mail-order electronic partsmongers is many of them have a minimum order of like 10 USD or so, and then there's shipping on top of that. 

I think Digikey has a zero minimum order, but I am not sure about that.

The surplus-selling places like Electronic Goldmine, or BGMicro, will tend to have better prices, but with limited selection,  compared to the strictly new parts sellers like Digikey or Jameco.  Actually, finding parts is a topic I have written a few words about before, here:
http://www.instructables.com/answers/Where-can-I-order-assorted-capacitors-resistors-/
+10000000
iceng2 years ago
Could you interrupt the black wire going to the bridge in the first pic.
Then try turning it on and see if it pops anything ?

Repeat the process with only the white wire detached please ?

A
PurpleMom (author)  iceng2 years ago
I tired both--same results--the breaker does not trip with only one or the other connected.
iceng PurpleMom2 years ago
One thing we can be sure of is it is not cord problem or grounded motor short.

iceng iceng2 years ago
Now lift the blue wire from the brush holder and try again please..

A
You're probably thinking the same thing I'm thinking.

I did a Google search on "electric lawnmower" + "bridge rectifier", and this,
http://www.tehhouse.us/electrical/lawn_mower/bandd/index.php
was one of the links that turned up.  I think there might be some clues therein.
PurpleMom (author)  Jack A Lopez2 years ago
This is a useful page, I wish I had found this when I was searching before. It helps my understanding. I bookmarked it.
zaronas2 years ago
if you do get a multimeter (which cheap ones are at max 20 bucks) if you go to harbor freight you cna probably find one for ten dollars or less, anyways when/ if you get one connect the two terminals to the end of the cord switch it to the ac mode, then have someone switch the switch to on and turn the motor see what that does
zaronas zaronas2 years ago
and multimeters can be used for lots of uses, when you set them to the resistance side (ohms measurer) you can check for onnectivity which is useful for checking all sorts of electronics, im sure lots of people can come up with more uses
Re-design2 years ago
When you move the blade does the motor turn? The reason I ask is I remember something about electric mowers having a centrifugal clutch as a safety feature. So if that's right the blade might be free but the motor locked up. I think that's what is wrong and not a short,
PurpleMom (author)  Re-design2 years ago
Ok don't laugh if I'm really ignorant about motors--The magnet is a cylinder on the outside. There is a shaft going through the center, and when I turn the blades I can see this part turning in unison.
Then your motor is not locked and that's not your problem.
Burf2 years ago
Make sure its unplugged and then lean close to the motor and see if you can detect a burnt odor. If so, you likely have a short in the windings on the rotor or stator, which means it will need to be replaced.
PurpleMom (author)  Burf2 years ago
There was no burning smell, when it first happened or when I tried to start it later.
Does it trip only when its switched on ?
PurpleMom (author)  steveastrouk2 years ago
Yes, it's unplugged, I plug it in, but when I push the on button it pops the breaker immediately without even a sound from the mower.
OK, its not the power cord, its something after the switch, and could be the motor. See what Iceng's ideas do.