# Smoking Electric Mower



## thorold16 (Dec 15, 2016)

Dear Madam/Sir;

On my last cut of the season, I (unwisely) chose to mow wet grass with an electric mower - Black and Decker MM850. As result, the clumping of grass stopped the blade, smoke emitted from the motor and blew the fuse.
I cleaned out the grass from underneath mower and replaced the fuse - of which (again) blew upon activating on/off switch.

Side note: I inherited this mower and use it as a "back-up" to a gasoline engine mower - of which doesn't get used much; point being, it was in very good condition. 
Brushes are hardly worn, no signs of melting/disintegration to visible/unconcealed wiring or parts. 
Limited in my knowledge of electricity/electric mowers. Any suggestions on what to inspect and equipment needed, e.g., type of meter - or, does the smoke indicate a serious problem that would be costly to repair/replace parts? 
Thank you for your consideration.


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## Corday (Mar 3, 2010)

See if a wire has come lose and is touching a ground. Also backtrack the wire from the fuse and see the status.


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## AVB (Nov 28, 2014)

You can the bridge rectifier to see if it shorted out. Other than that then the armature would shorted from overheating. @ about $160 it can be an expensive fix. Even the bridge rectifier will set you back by about $20.00 depending where you source it.BTW this is a DC motor so if replacing the rectifier don't reverse the output leads.


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## AVB (Nov 28, 2014)

AVB said:


> You can the bridge rectifier to see if it shorted out. Other than that then the armature would shorted from overheating. @ about $160 it can be an expensive fix. Even the bridge rectifier will set you back by about $20.00 depending where you source it.BTW this is a DC motor so if replacing the rectifier don't reverse the output leads.


Wording correction ....

You can test the bridge rectifier to see if it shorted out.


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## SABL (Jul 4, 2008)

I'm a pessimist......you're looking at replacing the armature. Another good cause for ruining an armature is insufficient conductor size in the extension cord you're using. That mower will need a 14ga cord with a maximum length of 50'.....anything longer will need to be 12ga. Most home-owners buy 16ga cords for use around the house......serious no-no unless you are only using a small drill.


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## Corday (Mar 3, 2010)

I guess I go to the extreme. I have 2 50' 12 gauge extensions to get as far as I ever need to go and 1 25' 12 gauge for close jobs so I don't have to uncoil the big ones. thorold16; please post back so we can see how far you've gotten with the suggestions.


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## AVB (Nov 28, 2014)

And it is harder to find the larger cords most times. I do agree that the voltage drop on long runs as being a problem. And this voltage drop can also overheat wires. 

Now I am guilty of pushing too RF through too small of a coaxial cable. It is like Scotty said "She can't handle anymore, Captain." Forgot and push 1500 watts thru a 300 watt RG mini 8 coax. When I service the antenna system a couple months later the conductors were blacken and the dielectic show signs of melting. No wonder my SWR was more than usual. 

I have also seen 16 ga extension cord wires blacken that had too amperage was drawn though them.


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