I have an old Milwaukee 3/8" drill that had the reversing switch
disintegrate. The variable speed trigger still works. To avoid paying
$40 for a new control switch, I'd like to replace the reversing switch
function with a mini toggle switch. My question is how to rewire it?
There are 4 wires in the circuit - two from the brushes and two from
1) To reverse the rotation direction, do I just reverse the polarity
of the field connections with the respect to the brushes?
2) Are the field coils wired in parallel to the brushes or in series?
Thanks in advance.
On Tue, 27 Nov 2007 14:17:26 -0800, Travelover wrote:
How is the present switch wired? How many terminals are there? Is the
current switch SPST or DPDT?
I would take the switch to your local electronics shop and see if they
can help you find an appropriate switch and maybe even give you some
ideas on how to wire.
The current reversing switch has a rotating contact assembly, but because it
fell apart, it is impossible for me to tell if it functioned as a SPST or
DPDT. There are four terminals.
If I knew how the field should be wired, I can duplicate function with a
To reverse rotation, reverse the connections of the field with respect to
the brushes, as you said.
The field coils are connected in series with the brushes.
A common DPDT switch will be good for a reversing switch. One without a
center OFF position is best. Wires from the brushes should go to the common
terminals, normally in the center. Wires from the field coils should go to
one pair of the other terminals and two short wires crossed over in an X to
the other pair of terminals. Double check that you never get a dead short
between the brush leads or between the field coil leads in any switch
position and you should be good to go. If it should make it any easier to
connect you can interchange the brush wires with the field coil wires on the
Who in the world told you the switch was that pricey? I have a 3/8
Milwaukee that used up the reversing switch a few years ago, and IIRC
the price then was about $8. Shop around, maybe some electronic
surplus might have what you need. Good luck/\\.
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