Fred’s Steps – How to Check 120V and 240V Outlets

Below we’ll outline how to check 120V and 240V outlets. We prefer to use an analog meter. Analog meters are more accurate and will catch voltage drops. Safety First – keep your fingers clear of the metal meter leads and do not allow the leads to touch each other when you’re checking a live outlet. To see these steps in action feel free to follow or continue reading below.

How to Check 120V and 240V Outlets

Fred’s Appliance Academy recommends the following steps when checking 120 volt and 240 volt outlets.

How to Check 120 Volt Outlet

Set your multimeter to AC at 200 volts or higher.
Between H and N there should be 120 volts +/- 10%
Between N and G there should be 0 volts
Between G and H there should be 120 volts +/- 10%
Any issue should be labeled properly. Don’t use terms like ‘bad’. Instead, you can state that the 120V outlet is Correct, or has an Open Ground, Open Neutral, Open Hot, Hot/Ground Reversed, or Hot/Neutral Reversed.

How to Check 240 Volt Outlet

Unlike 120V outlets, do not check 240V outlets at the outlet. Leads on the average meter are not long enough to make a good connection. We recommend checking for voltage at the terminal block.

3-Prong

To check a 3-prong outlet, start by unplugging the cord
Locate the terminal block, then remove the screw and cover
Verify the cord is installed correctly
Set your multimeter to Voltage 600
Plug the cord back in
Between L1 and L2 there should be 240 volts +/- 10%
Between L1 and N there should be 120 volts +/- 10%
Between L2 and N there should be 120 volts +/- 10%
Any issue should be properly labeled. On 240V 3-prong outlets you can state that the outlet is Correct, or has an Open Neutral, Open Ground, or that the line is Missing or Open.

4-Prong

To check a 4-prong outlet, start by unplugging the cord
Locate the terminal block, then remove the screw and cover
Verify the cord is installed correctly
Set your multimeter to Voltage 600
Plug the cord back in
Between L1 and N there should be 120 volts +/- 10%
Between L2 and N there should be 120 volts +/- 10%
Between L1 and L2 there should be 240 volts +/- 10%
Between L1 and G there should be 120 volts +/- 10%
Between L2 and G there should be 120 volts +/- 10%
Between N and G there should be 0 volts
Any issue should be properly labeled. On 240V 4-prong outlets, you can state that the outlet is Correct, or has an open L1 & L2, Open L1 or L2 and Ground, Open Neutral, Open Ground and Neutral, or Open Ground.