Rednadnerb wrote:
Clearing out the garage. I have an electric strimmer that was hardly ever used but has been hanging up for about 10 years. When I plug it in and switch it on the motor turns but slow and sluggishly. Is it worth opening up and spraying with WD40 or should I just put it straight in the bin?

1) Bearing check.

Strimmer is direct drive, no gear box. Check by rotating the
working end, that rotation works freely. Listen for grinding
noises from the brush assembly in the motor housing. There should
be no "critching" nor grinding.

2) Ohmic switch.

Unlikely to be a bad switch. You could use an ohmmeter on
the switch if you suspect otherwise.

3) Bad brushes.

This is the number one reason for strimmer failure.
The brushes wear down, being carbon graphite and pressing
against the commutator. Sometimes one brush wears more than
the other.

At the store, they sell so many brushes, they keep a tray of
them under the front counter, so they don't have to walk back
into the parts aisles to get them.

On the old B&D, a portion of the brush holder would melt
from the heat. The unit was then, unrepairable. For a while,
I would send people away if they asked me to fix those.

My current (non B&D) is around 30 years old, and the plastic
main housing, a portion cracked off the other day. Other than that,
no sign of brush problems yet. Full power available.

When you go to the B&D/Dewalt store to buy a pair of brushes,
don't forget to ask for "two crimps" to go with the "two brushes"
you are buying. The crimps are necessary to join the brushes
to the wiring. You have to know how to crimp, for the repair
to be successful. I didn't have the right tool, the last one
I did, but the crimp turned out very nice anyway, using
a larger tool I did have. Not all my crimps are "pretty", and
I've also managed to do some that any QA person would reject :-)

*Do not* succumb to the temptation to "clean the commutator".

The only time you should pay attention to that array of
shiny metal plates where the brushes touch, is if it is
obvious that some burrs on the commutator, are tearing
brushes apart. And causing premature failure and ohmic
contact. Even if you see burrs, it can be almost impossible
to do anything about it, without ruining something in the process.

You can only do a limited number of brush changeouts, before
you have to replace the wiring harness to get enough wire
to crimp in the new brush. If the brush contact had been
done a different way, you could "deal with" bad commutator,
by just frequent brush changes.

On big motors, the commutator plates are thick. Thick enough
that the commutator can be machined on a lathe. All metal
shavings must be carefully removed, if/when doing this. Only
a large motor shop would have the setup for large motor
commutator turning.

On a small motor commutator, it is too easy to leave burrs
on the edges of the commutator plates. Even the act of
cleaning it using DIY techniques, can do more damage than good.
There's not enough metal, for turning it down.

Don't touch that part, unless it's obvious the commutator
is so bad, it'll rip the brushes apart on first powerup.
Don't spray any crap on there either. Not even contact
cleaner! OK ? The brushes will eventually conform to the
pattern of grooves in the commutators, as the brush will
wear down until it seats and mates nicely with its new
neighbor.

The odds of being able to buy a replacement rotor assembly
should be almost zero. And if one is offered, it'll be
expensive (to encourage you to throw away the strimmer
and buy a new one). If I needed one, I'd just see if there
was a junker I could acquire and do a swap.

Paul