Saturday, October 31, 2009

Handy home-made tool; fixing a broken wire

Table of Contents

Important note: if you have a question to ask, please ask it at Lawn Mower Forum, either in the Black & Decker area or the Electric & Battery Operated area at that website. I apologize for being unable to handle individual requests for help posted on this blog or sent by email.
Handy tool for propping mower cover open

I'll start by saying that it's a real good idea to make a tool like this because it relieves stress on the wiring and connections when you have the top cover open.  By using a tool like this, hopefully you won't bend and break one of the wires like I did.

When opening the mower cover, I used to let the wiring and cables support the weight of the cover.  In my defense, I'll say that the wiring certainly looked sturdy enough and up for the task.  AWG 10 wire is fairly hefty and strong, but I wasn't aware of the short length of solid AWG 24 that was the weak link in this system.  While replacing the broken wire, I made a prop tool to support the cover as shown in the photos below.

The pictures pretty much tell you all you need to know to make one of these yourself.  I'll just add that (1) about 15 inches between the two end slots seems to work pretty well, and (2) when you use one of these, use a small tool or pen as shown in the second photo to keep the cover from sliding off the mower.


Fixing a broken wire

Here is something you shouldn't have to worry about if you either:

1. Use the cover prop tool described above, or
2. Don't remove the cover from your mower in the first place.

Since I did neither of these before now, a wire broke and needed to be fixed.  The break happened within the white insulated part of the wiring, between the battery "-" terminal and Main Circuit Board:

Note, this is part of a wire assembly that runs:
1. From the battery "-" terminal to the Main Circuit Board, and
2. From the battery "-" terminal to the motor "-" terminal

Since the break was not between the battery and motor, the mower would actually run.  However, the broken wire was part of the braking system, so when the mower was shut off it would take 10 seconds or so to spin down.  Normally the brake stops the mower within 1 second.

Here is the complete (but broken) wire assembly, removed from the mower:

An close up look at the break reveals two wires, a small AWG 24 solid (hence not too flexible) wire had been crimped into an AWG 10 stranded cable.  Repeated flexing or stressing at this connection by my repeated removal of the cover was almost surely the cause.
 Not sure why there is this combination of small and large wiring here, it probably has something to do with the braking action that stops the motor by shorting it through this wire assembly.  Best thing is to reconnect these wires back together, but I don't have whatever tool was used to press the small wire into the strands of the larger cable.  Instead, I used a soldering iron (40 W) to redo the connection:
Add about a 1/8" - 3/16" or so thick coating of hot-melt glue around the joint to prevent flexing, and we were good to go!