Grinder Repair – Replacing the Switch Lever (Makita Part # 418727-2)

Hi, I’m Mark from
In this video, I’m going to show you how to replace the switch lever in a Makita grinder.
The on/off switch on many Makita grinders is made up of three components: The switch
button, the switch lever, and the switch itself. The switch lever transfers the motion (of
turning the switch button on) back to the switch itself. Common problems with the switch
lever, is that it breaks where the switch button attaches to it, or it will break where
the tension spring attaches. Replacing the switch lever is easy to do and I am going
to show you how. Switch levers, as well as many other parts can be found on our website. Let’s get started. I’ll begin by removing
the side handle and the guard. The gearbox housing is held in place with four screws.
I’ll go ahead and remove those. Now, I can remove the rear housing. It is held in place
with a single screw. Now, I’ll move the brush springs to the side of the brush holder.
This will remove the tension from the brushes so they are not pressing against the armature.
I’ll do this on both sides. With the tension removed from the brushes, now I can go ahead
and remove the armature assembly. Now I’ll remove the baffle plate. It’s held in place
with two screws. Now, I’ll remove the switch button. To do that I hold it in the off position
as I push forward on the switch lever. When you hear it “click,” you can now remove
the switch button. Now, I’ll remove the field from the motor housing. The first thing
I’ll want to do is disconnect each of the wire connections. You’ll want to take note
of the location of each wire for reassembly. With the wires disconnected, now I can remove
the field from the motor housing. The easiest way to do this is to tap the housing against
a table until the field slides out. It’s in there pretty firmly. Now, I’ll move the
edge of the housing against the table to remove the field the rest of the way. Now, we can remove the switch
lever. I’ll use a pair of pliers to pull it away from the housing, and pull it out
and give it a little twist to remove it from the housing. Now, we can install the new switch lever.
Before I do though, I need to transfer the spring from the old lever to the new one.
Now, I’ll install the new lever into the housing. Now, I’ll install the field back
into the motor housing. As I do this, I need to thread the wires from the field back through
the openings on the motor housing. I want the side of the field with the two red wires
to line up with the sides where the connections for those wires are on the switch. I also
have the two black wires. One of the black wires hooks to the brush holder, on the same
side of the motor housing as the switch, and the other black wire on the opposite side.
As I thread the wires through, I find it works best to use a long screwdriver to help align
the wires with the openings as I install the field. With the wires aligned, now I’ll
go ahead and push the field the rest of the way into the housing. Now, I’ll reconnect
each of the field wires. The two red wires go to the connection on the switch. I’ll
loop these wires around to take up the excess. And the black wires to the connections on
the brush holders. Then, again, I will just take up the excess; get it out of the way.
Now, I can reinstall the switch button. To do that I push the switch lever all the way
forward and then align the hook, on the back of the switch button, with the opening in
the switch lever. Now, I’ll push the switch lever up against the hook on the switch button,
and then release the lever. Now, I’ll replace the baffle plate. Now, we can install the
armature assembly back into the grinder. I’ll reinstall the gear housing assembly to the
motor assembly and secure it with the four screws. Now, I’ll reposition the brush spring
back over the brush. Now, I’ll slide the rear cover back over the motor housing and
secure it with the screw. And I’ll finish up by installing the guard and the side handle. And that all it takes to replace the switch
lever on a Makita grinder. If you found this video helpful, be sure to give us a thumbs-up
and leave a comment.

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