How to Fix Electric Lawnmower (Rectifier) – Trips Circuit Breaker Short Circuit (Task Force)

So one day I was looking through the free section on craigslist and saw someone giving away a broken electric lawn mower.  Oddly enough, I noticed the address as the neighbor to one of my friends.  So I texted him and he walked over and snagged it for me.

I actually first wanted it so I could harvest the motor for another project but then I realized that I could fix it!  I had never worked on one before but I did some research and realized there aren’t many parts in these things and typically what breaks is the bridge rectifier.

Here is the exact one I purchased that you can get on amazon*:

The bridge rectifier is what converts the AC to DC.  It is needed because the motor is a direct current (DC) motor.  The previous owner mentioned in their craigslist ad that they were using it through a high patch of grass and the mower just died.  After I opened it up saw that the heat sink for the bridge rectifier was not attached and that the rectifier was shorted, I had my answer.  They went through the high grass, put more strain on the mower, which drew more current through the rectifier, which caused it to heat up, and then it got too hot and damaged the internal diodes.  At least that is my theory.

Anyway, a few dollars and a new bridge rectifier (with some new thermal paste on the heat sink) and I have a working mower!

Here is a link to some very good thermal paste*. I had some old stuff laying around that I used.

Here is my youtube video describing the process of the repair.  This should be the same on pretty much any lawnmower that accepts an AC plug as its power source.

*As an Amazon Associate I earn from qualifying purchases.