How To Change a Micro Switch
Micro switches are typically used for safety circuits in an electrical control situation. These small switches have three connection points identified as N.O., N.C. and Common. The N.O. point is short for normally open, N.C. is normally closed and the common point is connected to both of these during the switches operation. At rest, the common point is connected to the normally closed side of the switch. When the lever is actuated that connection is broken and the common then connects to the normally open side. A typical connection for a micro switch is from the common terminal to the normally closed side. When the switch is activated that circuit will open or shut off and the electrical circuit that is controlled will be disabled. Does this Spark an idea?
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Instructions
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Remove all electrical power from the control circuit. Micro switches typically are used on low power electrical circuits. Shorting a power lead to ground could cause damage or blow a circuit fuse.
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2
Pull the spade connectors from the micro switch, using the small pliers, or remove the ring connectors using the small screwdriver. Identify the leads by making a mark with a pencil on a piece of clear tape. This can be NC, NO or COM for common. Attach the tape to the wire lead.
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3
Remove the small diameter mounting screws from the micro switches mounting plate. Some screws are held in place by only a threaded hole in the plate. Other screws may be backed up by a secondary set of small nuts on the backside of the metal holding plate. All micro switches will use two screws to secure the small switch in place.
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4
Align the new switch on the mounting plate and install the screws. Do not over tighten. Too much force on the screws may crack or break the thin plastic of the switch.
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Connect the wires back onto the switch in the correct position. Reapply the power and test the switch by activating the lever with your finger.
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Tips & Warnings
Crack housings on micro switches will contaminate the interior contacts. This can mimic a properly operational switch when in fact it is bad. Visually inspect the micro switch for any exterior damage.
