To test and replace a circuit breaker, follow the steps below.
Replace Circuit Breaker
Step 1- Locate the service box.
Find the electrical service box that contains the suspect breaker either in your house, or in the garage. Note: Sometimes the boxes can be hidden inside of a closet.
Step 2- Turn off main power.
Shut off the main breaker located outside the house that supplies power to the service box.
Step 3- Open the door or panel covering the breakers.
After the panel is open, test the wire going to the circuit breaker you are replacing to be certain the power is off. Use a multimeter in the high VAC range. Place one meter lead on a metal ground, and touch the other lead to the feeder wire that powers the circuit breaker. The reading should be zero volts, which indicates the power is off.
Step 4- Remove the feed wire if necessary.
Unscrew and pull out of the way the feed wire (if equipped) going to the circuit breaker you are replacing. There should be only one black wire unless you are replacing a double pole breaker.
Step 5 - Remove the circuit breaker.
Pull the circuit breaker outward to remove, as most breakers are seated on a lip at the bottom. Some breakers are screwed in and therefore you must remove the screw(s) before pulling it out.
Step 6 - Install new breaker.
Install the new circuit breaker with the same amp rating. Push the new breaker in place securely and reconnect the feeder wire(s) going to it if applicable. Reinstall the mount screws if removed in step 5.
Step 7- Restore power to the breaker box.
Turn the outside main circuit breaker on first, and then flip on the new circuit breaker you just replaced.
Note: If the new circuit breaker immediately trips, then you either have a shorted circuit or the power load on the breaker is too high. Further troubleshooting is required.
Step 8- Close the panel and test the new breaker.
If the circuit breaker is not tripping, close the panel and check the outlets and lights that are connected to the new breaker.
How to Test a Circuit Breaker
Step 1- Remove the circuit breaker.
Use the steps above to safely remove the circuit breaker from the panel.
Step 2- Set up the multimeter.
Set the multimeter to the lowest Ohms resistance range. You will be testing for continuity in the next step.
Step 3- Measure resistance across the breaker contacts.
Once the breaker is removed, find the metal prongs on each side of the breaker, and put a meter lead on each prong. Some breakers may have two wire terminal screws instead of the metal prongs.
Step 4- Read the test results.
You should read an open with the breaker off, and continuity with the breaker on. If you get no continuity in the "on" position, then the breaker is open electrically and will need replaced. If you read continuity in the "off" position then the breaker is shorted internally and would also require replacement.