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Testing and Replacing Switches

After getting flipped thousands of times, a switch can wear out. Unless the problem is a loose wire connection, there is usually no way to repair a faulty switch; you’ll need to replace it. It is easy to test switches and easy to replace them. If you want to replace your old switch with something more sophisticated— for example, a dimmer.

Caution! Hold only the metal flanges of the switch when pulling it out of a box. Be very careful not to touch the terminal screws or to allow the screws to touch the edge of the box.

Safe Use of a Continuity Tester - Never use a continuity tester on wires that might be live. Always shut off power and disconnect wires before testing. The continuity tester uses a battery that generates a small current to test for the flow of electricity from one point to another. It is not made to carry household current.

Use a neon tester... NOTE: Shut off power. Remove the cover plate and the screws holding the switch. Pull the switch out from the box. Turn the switch to OFF and restore power to the circuit. Touch the probes of a neon tester to the switch’s screw terminals. If the tester glows, the box has power. Turn the switch on. Touch the probes to the terminals again. If the tester glows this time, the switch is blown and must be replaced.

...or use a continuity tester. An easy way to test a switch is to use a continuity tester. Shut down the circuit leading to the switch and remove the switch from the box. Disconnect all wires. Attach the tester clip to one of the terminals and touch the probe to the other. If the switch is working, the tester will glow when the switch is on and not glow when the switch is off.

Test a three-way switch. To check out a three-way switch, shut off the circuit and attach the clip to the common terminal (it’s usually labeled on the switch body). Touch the probe to one of the other screw terminals and flip the switch. If it’s OK, the tester will light when touching one of the two terminals. Flip the switch. The tester should light when the other terminal is touched.

Test a switch/receptacle. To test a device that has both a switch and a receptacle, attach the continuity tester clip to one of the top (switch) terminals and touch the probe to the top terminal on the other side. If the switch is working, the tester will glow when the switch is on, and not glow when it is off.

1. To replace a switch, remove the old switch. NOTE: Shut off power. If a switch is damaged, remove the screws holding the switch to the box and gently pull out the device. Loosen the screw terminals and disconnect the wires.

2. Attach wires to the new switch. Inspect the wires in the box and wrap any damaged insulation with electrical tape. Attach the wires to the terminals of the new switch and wrap electrical tape around the body of the switch so the terminals are covered.

3. Reinstall the switch. Carefully tuck the wires and switch back into the box and connect the switch to the box by tightening the mounting screws. Don’t force anything; switches crack easily.

Test a fixture-mounted switch. Small switches that mount on fixtures work by pull chain, flipping up and down, or twisting. These switches are not long-lived, so if the light does not work and the bulb is not blown, there is a good chance that the problem is with the switch. To test, shut off power to the fixture (or unplug it). Remove the connectors holding the switch’s leads. Leave the bare wires twisted together, and arrange them so the connections are not in danger of touching each other or anything else. Restore power to the fixture and carefully touch a neon tester to the connections. If the switch is turned on and the tester lights, the switch is bad.

Replace a fixture-mounted switch. NOTE: Shut off power. Remove the fixture and disconnect the wires. Release the pull-chain switch by loosening the terminal screws and two screws in the base of the socket. Install a replacement switch and remount the fixture. Other porcelain fixtures have an integrated switch. In such cases, replace the entire fixture. Lamp pull chains cannot be repaired. Buy a new pull-chain socket and replace the old one.

Testing and Replacing Receptacles

Receptacles can be damaged in IV ways that are not readily apparent. Small cracks can lead to a short. As receptacles grow old, they may hold plugs in place less firmly. The good news is that receptacles are inexpensive and easy to replace. Don’t hesitate to replace one for any reason, such as because it is paint-glopped or the wrong color. However, if you want to replace your receptacle with one of a different type—for example, replace an ungrounded receptacle with a grounded one.

1. To test for a faulty receptacle, see if receptacle is live. With the power to the circuit on, insert one probe of a neon tester into each slot of the receptacle. Do not touch the metal probes; only touch the insulated wires of the tester. If the tester glows, the receptacle is working. Test both plugs of a duplex receptacle.

2. Test for power to the box. If the receptacle is not live, check its power source. Shut off power to the outlet at the service panel, remove the cover plate, disconnect the screws holding the receptacle to the box, and pull the receptacle out. Restore power, and touch one probe of the neon tester to a brass screw terminal and the other to a silver-colored terminal. The tester light will glow if power is coming to the receptacle.

1 .To replace a receptacle, remove the old receptacle. NOTE: Shut off power. Note which wires are attached to which terminals. If necessary, make notations on pieces of tape and wrap them on the wires. Loosen the terminal screws and disconnect the wires.

2. Wire the new receptacle. Inspect the wires in the box, and wrap electrical tape around any damaged insulation. Attach the wires to the receptacle, positioning each wire so it hooks clockwise on the terminal screw. Firmly tighten the terminal screws.

3. Wrap with tape and install. Wrap the body of the receptacle with electrical tape, so that all the terminals are covered. Carefully tuck the wires and the receptacle into the box and connect the receptacle to the box by tightening the mounting screws. Don’t force the receptacle into place—it may crack.

Test for grounding and polarization. Do not turn off the power. Insert one prong of a neon tester into the short (hot) slot and the other into the grounding hole. If the tester glows, the receptacle is grounded and the slots are polarized. If the tester doesn’t glow, put one probe in the grounding hole, the other in the long slot. If the tester glows, hot and neutral wires are reversed. If the tester doesn’t glow in either place, the device isn’t grounded.

Test a two-slot receptacle. With the power on, insert one probe of a neon tester into the short (hot) slot, and touch the other probe to the cover plate screw (above). The screw head must be clean and paint-free. Or, remove the cover plate and insert one probe in the short slot and touch the other to the metal box (above right). If the neon tester glows, the box is grounded, and you can install a grounded three-hole receptacle. If the tester doesn’t glow, insert one prong into the long (neutral) slot and touch the other to the cover-plate screw or the box. If the tester glows, the box is grounded, but the receptacle is not correctly polarized; the hot and neutral wires are reversed. If the tester doesn’t glow in either position, the box is not grounded. Do not install a three-hole receptacle.

Using a Receptacle Analyzer - With this handy device, you can perform a series of tests almost instantly without having to dismantle anything. Leave the power on, but unplug all equipment and flip all switches to off on the circuit of the receptacle you will be testing. Plug the analyzer in. A combination of glowing lights will tell you what is happening with your receptacle.

Troubleshooting Thermostats

A thermostat is a switch that senses temperature and turns your heater or air-conditioner on and off according to the control settings. Most homes have low-voltage units like the one described here. A transformer reduces power from 120 volts to around 24 volts and sends it to the thermostat. Some systems have two transformers: one for heating and one for air-conditioning. Possible causes of thermostat problems include faulty wiring, a corroded thermostat, and a worn-out transformer.

Anatomy of a thermostat - A low-voltage system begins with a transformer that is either mounted to a panel on the furnace or connected to an electrical box. Anywhere from two to six thin wires (depending on how many items are being controlled) lead to the thermostat base where they are connected to terminals. The thermostat body contains the heat-sensing device and the control dial. Because the voltage is so low, it is not necessary to shut off power to the thermostat while working on it—unless you are working on the transformer.

1. Clean the thermostat. Dust can cause a thermostat to malfunction. Remove the cover plate and brush the inner workings with an artist’s brush. Pay special attention to dust and dirt on contacts.

2. Remove the body. Unscrew the screws that hold the thermostat body to the base, and pull the body away. Check to see that the base is securely fastened to the wall. If it is loose, the thermostat could tilt, which would throw off the settings. Blow on the body to remove more dust, but do not handle the parts inside—they are sensitive.

3. Inspect connections to the base. Look for loose, corroded, or broken wires coming into the base. If any are damaged, clip them, strip insulation from the ends, and reattach. Tighten all the terminal screws to make sure the connections are secure.

4. Hot-wire the terminals. Cut a short piece of wire and strip insulation from both ends. Use it to “jump” between terminals. Touch one end to the “R” terminal and one to “W,” and the heater’s burner should come on. Touch “Y” and “G,” and the fan should come on. If they do not, the thermostat is faulty and should be replaced.

5. Test the transformer. If the thermostat checks out, test the transformer. Touch one probe of a voltmeter or multitester to each of the low-voltage terminals on the transformer. Set dial to ACV 50. If the meter does not detect current, the transformer is defective and needs to be replaced.

6. Check power to transformer. Before you go out and buy a new transformer, open up the transformer box and make sure that there is power leading to the transformer. Touch one probe of a neon tester to the hot wires and the other to the box (if grounded) or the neutral wires.

Installing a Programmable Thermostat - A programmable thermostat automatically changes the temperature in your home for sleeping and waking hours. It also can deliver different temperatures when you’re away. There are many options to choose from. Some control heat only and some also control air-conditioning. Some can be completely programmed in one sitting; others require a week-long run-through. Write down the brand names and model numbers of your old thermostat and heating and air-conditioning units. Take this list when you shop for a thermostat to assure it will be compatible with your system. Here is a guide for installation, but follow the manufacturer’s instructions that come with the unit.

Removal and installation - As you remove wires from the old thermostat, label them. Remove the old thermostat. Pull the wires through the new wall plate and mount the plate securely to the wall. Check that it is level. Push any excess wire back into the wall and hook up the wires according to the manufacturer’s instructions. Attach the body to the cover plate. Set the clock and program the unit according to the manufacturer’s instructions. Attach the cover.

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