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Posted by on March 20, 2006    |    Leave a reply   

Wiring a switch can be a little more difficult than it seems at first, especially if the power tool manufacturer has suddenly changed out a 4-terminal switch for one with only two terminals. All is not lost, however. The two terminal switch will work perfectly in your power tool. The trick is in the wiring.

Why in the world would a power tool manufacturer like Makita, Bosch, or DeWALT decide to do a rotten thing like substituting a switch in the first place? First, a 2-terminal switch is cheaper to build than a 4-terminal switch. Power tool manufacturers generally don’t build switches, they instead purchase them in bulk from an electrical wholesaler. Sometimes the wholesaler will change a switch style or sometimes a power tool manufacturer will decide to replace an expensive switch with a more economical one. The advantage? Usually the savings get passed on to you, the end user.

So how, you ask, do you wire the thing? It’s easy.

A switch simply serves to repeatedly break and connect an electrical circuit. When the circuit is connected, the tool runs. When it’s not, the tool is stopped. The important thing when wiring your 2-wire switch is to complete the electrical circuit from the cord to the motor and back to the cord. Here’s a simple wiring diagram explaining the process:

Instead of wiring the cold (negative) motor wire back through the switch, you connect it to the second, usually black, wire on the cord. The electrical current enters the circuit through the white cord wire and meets up with the switch. From the switch, the current travels through the blue motor wire to the motor itself, providing power for the tool. From the motor, the current travels through the second blue wire, which when connected to the black cord wire allows the power to get back to the wall and complete the circuit. Pretty easy.

It’s always important to thoroughly test your power tool’s operation once you’re done installing the new switch. If your power tool features a rotating spindle, make sure that it spins in the proper direction. This is especially important with routers and saws because a bit or blade rotating in the wrong direction can be dangerous. If your tool is spinning the wrong direction, simply reverse the motor wires on the switch, thereby changing the polarity.

I hope that this little article has helped you wire your new switch, but if you’re still stuck feel free to ask for some help. You can always call us toll-free at eReplacementParts at 1-888-499-1974 or email us at and one of us will help you out. Best of luck.