Multimeter safety tips for all appliance troubleshooting

When your dryer won’t heat, your oven won’t turn on, or your fridge isn’t running, it’s time to grab one small tool to help you find the problem fast: a multimeter.

This handy device can easily help pinpoint the problem so you can fix it fast — as long as you know what you’re doing.

Whether you’ve never used a multimeter before or are an experienced professional, it’s important to familiarize yourself with tips for proper use so you can keep yourself safe.

If you need replacement parts for any of your home appliances, you can use your model number to find what you’re looking for at AppliancePartsPros.com. We also have thousands of free DIY troubleshooting and repair guides to help you fix your appliances yourself!

Know your multimeter settings

Before you start testing anything, take a moment to get familiar with your multimeter. 

There are two main types of multimeters: analog and digital. Digital multimeters are more common and tend to be easier to read, while analog ones use a needle gauge. If you’re new to multimeters, it’s best to go with digital.

Basic settings you’ll use:

• AC voltage (V~ or V AC): Used to test wall outlets and appliances that run on household current
• DC voltage (V— or V DC): Used for batteries and some electronic parts inside appliances
• Resistance (Ω): Measures the amount of difficulty an electric current has when it travels along a wire or another conductor. It’s used to verify that the actual resistance value of resistors matches the specified or labeled resistance. It can also identify if a resistor is open (infinite or OL) or shorted (0 resistance).
• Continuity: A smaller resistance measurement that checks for an uninterrupted path for electrical current through a wire or cable.

Avoid testing live circuits unless necessary

During most troubleshooting, you can get the information you need by testing parts with the power off. However, in rare cases you might need to check if electricity is flowing to a part, like when troubleshooting a power supply issue. 

If you must test live voltage, be sure to follow these safety precautions.

• Check your meter’s voltage rating to make sure it can handle the voltage you’re testing. Household appliances typically use 120V or 240V, so your multimeter should be rated accordingly.
• If you can, use one hand at a time. This reduces the risk of electrical current passing through your chest. Keep your other hand away from the appliance or in your pocket. If this isn’t possible, clip a lead onto the first measurement point (preferably not the one that’s hot), then pick up the other lead and hold it (or clip it) to the other reference point.
• Wear insulated gloves and rubber-soled shoes. These add an extra layer of protection against shocks.
• Secure the probes first. If you’re testing a live outlet or wiring, insert the black (COM) probe into the neutral or ground slot first, then place the red probe on the hot connection. This minimizes the risk of an accidental short.
• Never let the probes touch each other. If the metal tips touch while testing live voltage, they could cause a dangerous spark or short circuit.

Read more: How To Use A Multimeter To Check Appliance Parts

Watch out for capacitors & discharge them before testing

Some appliances, like microwaves, refrigerators, and air conditioners, contain capacitors that store electricity even after the appliance is unplugged. These parts can hold a dangerous charge for a long time, so you may need to discharge them before testing.

How to safely handle capacitors

• Never touch the terminals directly. Even a partially charged capacitor can deliver a shock.
• Always use insulated tools and wear rubber gloves. This reduces the risk of accidental discharge.
• If a capacitor is swollen or leaking, DO NOT test it. It should be replaced immediately.

How to safely discharge a capacitor

1. Unplug the appliance and wait a few minutes. Some capacitors discharge naturally over time.
2. Find the capacitor. It’s usually a cylindrical part near the motor or power supply.
3. Use an insulated screwdriver or a resistor to do the following:
   • Screwdriver method: Hold the insulated handle and touch the metal shaft to both capacitor terminals at the same time. This will quickly release the stored charge.
   • Resistor method: Attach a 20,000-ohm, 2-watt resistor across the terminals with insulated leads. This will slowly discharge the capacitor.
4. Double-check with your multimeter by setting it to DC volts and testing the terminals. If the reading is close to zero, then the capacitor is discharged.

How to test a capacitor with a multimeter

1. Set the meter to capacitance mode (if available).
2. Disconnect the capacitor from the circuit.
3. Place the probes on the terminals. A good capacitor should show a reading close to its rated capacitance (marked on the capacitor body). If the reading is far off or nonexistent, then the capacitor is bad and should be replaced.

Read more: Must-Have Tools for Appliance Repair – DIY For Beginners

More safety tips

• If the appliance has recently been used, give it plenty of time to cool down before working on it. 
• Shut off the gas supply to prevent any gas leaks while you work. 
• Take your time while working to prevent accidents and personal injuries. Rushing is the enemy of precision.
• Work in a well-lit area so you can see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with wet hands. Make sure the work area is completely dry.
• Check the user manual to see if there are specific installation or safety instructions related to your appliance or replacement part. 
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause personal injury.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Always take photos or make a note of wiring terminals or other connections before disconnecting them to make reassembly easier.
• Don’t test live voltage with a multimeter if you’re unfamiliar with how to prevent short-circuiting.

How to use a multimeter to test appliances

When an electric appliance isn’t working, a multimeter can help you quickly figure out which part is to blame. Here’s what to know about checking parts with your meter.

Check wires and connections

Sometimes, an appliance problem isn’t due to a failed part but rather a broken wire, loose connection, or corroded terminal. These issues can interrupt power flow and make an appliance act like it’s dead or malfunctioning. 

You can use a multimeter to confirm if a wire or connection is faulty.

1. Visually inspect the wiring. Look for frayed wires, burn marks, or corrosion. Check terminal connections to see if they’re loose or discolored. Clean (only with electrical contact spray) and/or replace any problem areas before moving forward.
2. Set your multimeter to continuity mode.
3. Touch one meter probe to each end of the wire. If the meter beeps, then the wire is good. If there’s no beep from the meter, then the wire is broken or disconnected.

If an appliance isn’t getting power, you may need to check if voltage is reaching certain points.

1. Set the multimeter to the correct voltage setting (AC or DC — check the appliance to find which one you need to test).
2. Carefully place one meter probe on the power source and the other on the connection point.

If there’s no voltage, then the issue is upstream: either a bad switch, control board, or power cord.

Test with multimeter functions

You can use your multimeter’s functions to test various items in your home. Here’s a rundown of what’s involved during each test. 

AC voltage (V~ or V AC)

AC voltage is used to test wall outlets and appliances that run on household current. 

How to test AC voltage

1. Set the multimeter to AC voltage mode.
2. Insert the black probe into the neutral or ground slot, and place the red probe on the hot connection. A standard outlet should read around 120V or 240V, depending on the appliance.

DC voltage (V— or V DC)

DC voltage is used for testing batteries, motors and other electronic parts inside appliances. 

How to test DC voltage

1. Set the multimeter to DC voltage mode.
2. Place the black probe on the negative terminal and the red probe on the positive terminal. A good battery or power supply should show the expected voltage range based on its rating.

Resistance (Ω)

Resistance determines if a part — such as a heating element or motor winding — is intact. 

How to test resistance

1. Set the multimeter to resistance mode.
2. Disconnect the part from the power source.
3. Place the meter probes on both terminals. 
4. Check the reading on the meter. A normal resistance reading depends on the part’s specifications. If the meter shows infinite resistance (OL), it means the part is broken.

Continuity

Checking for continuity determines if a circuit or wire is complete. 

How to test for continuity

1. Make sure the power supply is off.
2. Set the multimeter to continuity mode.
3. Touch the multimeter probes to both ends of the wire or fuse and listen for a beep from the meter. A beeping sound means the circuit is complete, while no sound indicates a break or bad connection.

Read more: Tool Maintenance 101: The Basics You Need To Know

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