(Black & Decker MM875) Electric lawn mower troubleshoot

[@cchemmes-seeseeart3948]

I have the same mower, purchased in 2010, & the only work ever needed was to replace the plastic retaining washer once, & the brushes once. I'm replacing the brushes now again. The video helped to understand the mower & parts & issues, in general. I need just a bit more precise/ exact detail on how a few things are done, in checking wires with the multi-meter, & installing the brushes. I "kind of' "pretty much" get it, but for actually doing the job, (changing brushes) right now, for me, I need more exact, precise details to feel like I'm fully ready to do the job right & without issues. Just a couple more sentences & the video would have been absolutely perfect for me. But for what you did show, I'm thankful for the video.

[@HomeownerDIY]

Thanks for your comment, for the brushe(s) if you pause the video at 9:17, you can see the brush inside its metal housing. The spring keeps tension on the brush. To install you need to compress the spring with your finger. Between 9:17-11:00 I show how to install in the brush. l am sure you are really over thinking this. If you need a video, I can make a QTOW video for you. As for the multi-meter, The only check I do is a continuity test. Here is a link to the video: #QTOW# Continuity tests kzbin.info/www/bejne/rpDUZYiCfKtmgtE Please let me know if you need any other information.

[@cchemmes-seeseeart3948]

@@HomeownerDIY Thanks. I'm going to try to replace the brushes tomorrow, & see how it goes?? Hopefully, it will be straightforward.

[@HomeownerDIY]

@@cchemmes-seeseeart3948 Look at my video when you do it and I am sure you will be fine. This electric mower is really basic to work on. Good luck sir!

[@corylee1800]

Thankyou for the fix guide

[@HomeownerDIY]

If you have any questions, please dont hesitate to ask!

[@fugii8062]

Great vid thanks due🎉

[@diydrivenGA]

I recently picked up a Sunjoe mower and used the two extension cords that I had on had....a 50 and a 100 14 gauge (orange). Proceeded to burn out the motor. Replaced the motor and now am using a 12 guage. (yellow and much more expensive). I think the cord plays a big role.

[@HomeownerDIY]

Thanks for your comment, sounds like 14 gauge wire at 150 feet is too small to power a mower. 12 gauge is a bigger wire so it will have less resistance over the same length. Well live and learn!

[@SyzygyD]

My first big problem was a pin in the right angle trigger switch fell out. Where in the grass, who know? Lucky, I found someone with the same model on kijiji with dying issues. Tried to switch out the switch assembly but between the corrosion and the special screws, I ended up swapping out the whole fork assembly. (Getting the switch replacement, hoo boy, scarce) Now, having hit things in the past and taller grass, I’ve sent off via Amazon for the fan by the blade (one fin broken) and the insulator that clips the blade, the edges having worn from stress and impact. Parts two weeks to arrival. Really think I should have maybe just got a replacement mower.

[@HomeownerDIY]

Thanks for your comment, if you went through that much it sounds like a new mower would been easier hahaha!! Its part of learning. The parts for the mower arent expensive but how much time and effort is needed? Take the experience and apply it to the next job!

[@Africa1000]

Good video. Apparently the rectifier sometimes burns out and will need replacing.

[@HomeownerDIY]

Parts whether their mechcanical or electrical, will need replacing at somepoint. Great thing about an electric mower is that its a simple machine.

[@Africa1000]

​@@HomeownerDIY Absolutely true. I have a corded electric, petrol and a push mower. I even own an ancient scythe. Each has advantages and disadvantages but there is something aesthetically beautiful about the combination of simplicity and efficiency of a corded mower!

[@HomeownerDIY]

@@Africa1000 Thanks for your comment, one other thing about a corded mower, you dont have to replace the battery on a regular basis! Not sure what a battery costs for a mower, but looking at an EV battery replacement cost is enough to make most people cry.

[@Africa1000]

@@HomeownerDIY Precisely! I don't think I'll ever be persuaded to buy a battery over a standard electric corded mower. Once you've sorted out your extension leads and get the technique right an electric mower can be surprisingly effective and versatile!

[@weirdphax5406]

Good man right here🎉

[@1Patient]

I have the same mower. The "Fan" 13:57 part attached to cutting blade under deck of mower is broken. Oh, and that "sheer-washer" you spoke of 12:04 what part numbers are we talking about 🤔? I am trying to find a cost effective way of replaying it myself. How much should I pay? Canadian $ for a new Fan and Sheer-Washer? Thanks.

[@HomeownerDIY]

Thanks for your question, try Reliable parts in Canada, and if youre near the US border, Ereplacementparts can send parts to a box that you can pick up. I think the shipping is the biggest killer getting something out of the country. The plastic parts are relatively cheap.

[@1Patient]

Wow, thanks for the quick reply. I just wanted you to know your video was well done. I like the way you troubleshooted the problems and solve them. That was a good tip about sharpening the blade and checking the brushes for ware. Just a suggestion, I would like to see the part numbers for the items you discussed in your video. Brushes fan sheer washer switch. Okay thanks again. Have a good one.

[@HomeownerDIY]

I sheer washer is called officially a 'blade insulator' Dewalt makes them. Start with that as a search. I bought them ereplacementparts.

[@lastfanstanding999]

How many blades have you gone through ?😊

[@HomeownerDIY]

Thanks for your question, l am on our second blade. I will sharpen the blade when it gets dinged up from usage. Having an area similiar to a soccer field will have blades last much longer than an area that is: uneven, full of rocks, roots or other foreign debris that is not soft like grass. I wouldnt say there is a rule of thumb for blade life because how often the mower is used, type of grass and terrain will all be factors for blade life. Hope that helps.

[@eternal1blue]

Good video thanks

[@eternal1blue]

Yes I looking for a corded mower not to many choices but bd seems a better choice than a rental

[@HomeownerDIY]

I dont think mowers really change in quality when it comes to manufacture. Not an expert but this one has been running for over 20 years.

[@Spiritgumm]

Old B&D mower was working normally, suddenly stopped. I checked the rectifer with switch on, power seems to be going thru it. There's about half-inch left on the brushes and wires are firmly attached. Is that enough wear to cause a stoppage? I've read elsewhere that worn brushes will cause intermittent running issues at first.

[@HomeownerDIY]

Thanks for you question, a half inch l think is fine, do you notice any burn marks or pitting where the brushes and commutator meet? Is there a lot of debris in the mower that can cause the brushes to make intermittent contact?

[@Spiritgumm]

@@HomeownerDIY The ends were abit black and curved, but no pitting. When I removed the hood over the motor area, I was surprised to see so much leaves/grass packed in there, but the motor itself looked okay, just a couple small cobwebs that weren't big enough to stop anything. The motor turns freely with the blade. Is there a way to test the brushes to see if power is getting to them? My impression is the electricity turns them into magnets which then spin the motor, so move the brushes out of the motor area and see if they hold a piece of metal?

[@HomeownerDIY]

Have you confirmed power is getting to the motor? A continuity test will tell you this. If yes: Do a continuity test on the brushes as well. Do you notice visually any burn marks or burn smell at the motor?

[@Spiritgumm]

@@HomeownerDIY I don't know what a continuity test is, but I tested the rectifer according to another video and my meter read 120 AC, and 107 DC. I phoned a Dewalt service center earlier today, and the only thing he could think of was that I had used the wrong power cord (which is true). I'm using light duty 100 foot 16 awg, when I should be using 14 awg. He said this would slowly kill the motor, causing some wire to pop. I asked if there was a way to test if power was getting to the brushes, but he wasn't allowed to give advice that might kill me, lol.

[@HomeownerDIY]

Check out this video for continuity tests: #QTOW# Continuity tests kzbin.info/www/bejne/rpDUZYiCfKtmgtE Probably easiest to take a cord plug it in the mower then use one of the prongs of the cord and test it on the wire going to the brush.Test both wires(both brushes) Make sure the level is pulled so the mower is "on".We are testing to see if power is getting to the brushes. If you were using a 16gauge cord, especially at 100ft, that would be a problem. The wires would get too hot because of resistanace. Please let me know the results.

[@pj808]

My black and decker started strong but now the power is weak. Do you know how to fix it?

[@HomeownerDIY]

Thanks for your question. What do you mean by started strong? Few years ago? After a few mins? What do you notice that has changed?

[@pj808]

Very sluggish but still cuts just not strong though when i first bought it any suggestions ​@HomeownerDIY

[@pj808]

@@HomeownerDIY do you know the issue

[@HomeownerDIY]

Have you confirmed its not this: #QTOW# Motor runs, blade doesnt spin(B&D MM 875) kzbin.info/www/bejne/gHq4koilaN1litE

[@byronemert7125]

My mm2000 b d blade is frozen will not turn manully

[@HomeownerDIY]

Thanks for your question, if you plug in the mower and hit the trigger, does the motor spin?

[@byronemert7125]

It tries to turn gets warm to the touch

[@HomeownerDIY]

@@byronemert7125 lf you take the cover off and expose the motor, can you spin it by hand? Can you see any burn marks on the wiring?

[@thembelaninicky8807]

My lawn mower start and stops.

[@HomeownerDIY]

Thanks for your question, my educated guess is the motor is full of debris. Grass between the brushes in the mower will cause issues. Take off the cover and clean out the mower first. Also check to see the wires for the brushes are still tight. Dry grass is a potential fire hazard as well. If that doesnt fix your problem, please let me know and we can address the problem further.