How to TEST an Underground Dog Fence (Hardware Issues)

After researching and comparing different kinds of fences, you’ve bought and installed an underground fence.

What if your dog keeps running out, or the transmitter is beeping?

How you test your underground fence will depend on if you’re just trying to make sure it still works, or if you’re trying to find where the underground wire is broken.

We’ll show you how to test an underground dog fence, how to make a test loop, and how to splice the wire so it works like new!

How to Test an Underground Dog Fence

lost dog poster
It’s heartbreaking to lose a family dog. Keep your dog safe by testing your invisible fence regularly to ensure it’s working.

Use a multimeter to test the continuity of the perimeter wire and the transmitter unit.

Test the batteries to ensure they’re charged. Test the collar with the included key to make sure it’s working.

Test the boundary width and collar strength. The boundary may be too narrow allowing the dog to jump over, or the correction level may be set too low to make it a deterrent.

Make a test loop to ensure that the transmitter is working properly and the collar is responding as it should.

Finally, test the wire for breaks using a break detector.

Once the break is located, splice in a new piece of wire and retest before burying the wire and plugging in the unit for the dog.

Worried about getting shocked?

Check out our article on How to Touch an Electric Fence Without Getting Shocked to learn how to repair or adjust your fence safely.

How to Test an Underground Fence – 4 Diagnostic Tests

dog in an underground invisible fence
Start by testing the collar and transmitter function before moving on to locating wire breaks.

Test With a Multimeter

Unplug the fence transmitter, remove the fence wire from the terminals, and let it sit for an hour before testing to discharge electricity.

Set the multimeter to the lowest ohms setting (omega symbol).

Your multimeter may have a dedicated continuity setting that looks like a resistor – a triangle with a crossed line coming out to the right or a zig-zag with a flat line at either end, similar to a heartbeat symbol.

  • Touch the leads together to confirm they’re working. They should read 0 or less than 1. Touch the leads to each wire terminal on the unplugged transmitter. Wait a few seconds to let the multimeter level out before reading.
  • The reading should be 0 to less than 1. 0 is perfect – that means there’s no resistance in the electrical flow of the unit. Somewhere around 1 means you should probably clean the terminals.
  • If the resistance is anywhere between 1 and 10, call the manufacturer to find out what could be causing a high level of resistance in the unit. The source may be why you’re having trouble causing you to test.

Next, test the underground wire. Do this by touching one lead to each end of the underground wire.

Give it a few seconds to charge the wire and read the results from one end to the other.

  • If the number is around 0, the wire is working properly.
  • If it’s over 1, you have a partial to a full break, depending on the level of resistance in the wire.

We always recommend cleaning terminals and wire ends before reading to make sure that you’re getting a good electrical reading that’s not impeded by dust and corrosion.

Read our related article on How to Test Dog Fence Wire With a Multimeter for a more exhaustive guide!

Test the Collar Battery

dog training with an invisible fence
The collar is integral to the function of the invisible fence, so if the battery is dead, the rest of the fence will not work.

How underground fences work can seem complicated, so before running a bunch of tests on the fence, you should make sure that the batteries on the collar are charged.

There will be a light on the collar to indicate if it’s charged or not, but if you’ve let the battery completely die, the light will die too.

You can also use the testing key that came with your dog’s collar to see if the indicator lights up when you approach or cross the battery.

If it doesn’t, change the battery and test again.

Charge the battery if you need to, or replace it if that’s necessary. 

Read More: How to Adjust Intensity of Invisible Fence Collar. It’s important that you find the right strength for your dog’s needs. Here’s how to find and adjust collar strength!

Test the Fence Transmitter

After you check the batteries you can make sure that the collar is connected to the working transmitter.

This can easily be done by proximity testing the collar. Make sure the battery is fresh before testing.

While holding it at your dog’s height, walk towards the invisible border. You should hear a beeping noise as you get closer. Test this out at several locations around your yard.

If you do hear the beeps, then your fence appears to be working properly. 

Test the Fit of the Receiver Collar 

If all of this so far seems to be working and you know that your dog has been properly trained, but your dog runs through invisible fence markers, you should make sure that the collar was on properly.

  • It should be a snug fit so that the prongs on the collar touch your dog’s skin. If your dog’s fur is very long or thick, you may need to shave a little of the neck or install longer prongs on the collar.
  • However, you want to be sure that you can fit two fingers in between the collar and your dog’s neck, this ensures that the collar will not choke your dog or create wounds from rubbing the skin.

The last thing you should check with the collar before moving on to the transmitter is to make sure that it is set to the appropriate shock level.

If it is set too low, your pup will be able to walk over the fence with no problems. 

You can also increase the boundary width so the dog can’t get so close to the wire.

Some dogs will jump right over if they know the shock period will be short. Making the boundary wider takes away the fun.

This is adjusted by a dial or up and down buttons on the transmitter.

If you are still looking for a great underground fence, check out our best underground dog fence picks tested and reviewed.

How to Find a Break in an Underground Fence

testing for current in a buried fence wire
There are a few ways that you can test to see if the wire is broken underground.

All buried wire invisible fence transmitters emit a loud alarm beep if the underground wire loop is broken or the wire ends become detached from the terminals.

However, if you feel the wire may be the problem and for some reason, the alarm has stopped working, you can test the wire using a multimeter as described above, or using one of these methods.

Make a Wire Test Loop

Unplug the existing fence wire from the transmitter wire terminals. Cut a short length of fence wire (around 6 feet) and plug it into the transmitter wire terminals.

If the unit doesn’t beep, it’s a good loop. You can also test the ends with a multimeter as described above to ensure there is no resistance in the wire.

Ensure the collar has a fresh battery and pass it over the wire.

You should hear a beep and see a light flash on the collar. You can also use the test key to verify that the wire activated the collar.

If this test works, you are confirming that the transmitter works if it’s paired with good wire.

If you’re not getting these results from your buried fence wire, it may have a short or a break in the wire.

Use a Break Detector

First, you’ll need to purchase an invisible fence break detector. This is a tool that measures the amount of AC voltage in an area.

When a wire is broken, no voltage can flow through, and the detector will not be able to find a current. 

There are many options available, and some can detect AC current up to two feet underground.

Before you use the detector, you’ll need to:

  1. Turn the transmitter off. 
  1. Connect the two clips on the detector to the underground wire transmitter. Use one clip for the in wire and one clip for the out. 
  1. Turn your detector on and adjust the volume. The detector will make a noise when the sensor is within a certain distance of the underground wire. 

This distance will vary depending on the brand, so make sure you check the instructions that come with the detector so you know that you have the sensor close enough to the ground.

  1. From here, walk along the path of the underground wire. You should hear a constant sound, which indicates that the wire is intact.
  1. If there is no sound coming from the detector, then there is indeed a break in the wire and further steps need to be taken.

How to Find a Wire Break

Now that you’ve determined there is something wrong with the wire and, not the transmitter, it’s time for the next steps. 

You can build your own locator with just an AM radio with an antenna, a 4-stroke lawnmower, and 20-30 feet of test wire.

The test wire can be some extra wire from the underground fence kit.

  1. Disconnect the transmitter from the underground fence. 
  1. Take one end of the test wire, loop it around the spark plug of the lawnmower, and connect the other end of the test wire to one of the ends of the underground wire.
  1. Turn your lawnmower on. This will provide a low-frequency static output to the underground wire. 
  1. Next, turn on your AM radio and tune it to 530 kHz. This is low enough to pick up the static that comes from the underground wire. 

It should be too low to pick up any radio shows, but if it does pick up a station, try other stations nearby until you find an empty station that also picks up the wire noise.

  1. As you move the radio over the wire and get closer to it, the static will increase. 
  1. Walk along the perimeter of the fence while listening to the static.
  1. You will find the break in the fence when the static stops.

For more clarity and visual examples, check out this video for plenty of examples and more help on how to do this.

You can also clearly hear the broken/disconnected alarm beep in the video.

How to Fix a Broken Underground Fence Wire

tools needed to fix a buried wire
Fixing an underground wire is easy once you locate the break.

Once you’ve located the break you can easily make a bypass to keep the fence running.

Because the wire should only be buried just under the surface of the soil, it’s easy to dig and rebury once it’s fixed.

Once you’ve located the break, unplug the fence and carefully dig up the wire. You’ll need enough uncovered that you can draw it up and work with it.

You will need a new piece of wire to splice into the old one. For a secure, waterproof connection you’ll need wire nuts and wire tape or a shrink tube.

  1. Clip the wire apart at the break, and cut out the broken length.
  2. Use wire strippers to remove about an inch of the wire insulation on each exposed end of the old length and the new piece.
  3. Twist the end of the old wire together with the new one until they are securely intertwined. If using a wire nut, put both ends into the nut and twist until it’s secured.
  4. Wrap all of the exposed wire with high-quality electric tape. This makes the splice stronger and helps secure it even further. It can help the splice be resistant to rain as well.
  5. Use a shrink sleeve and heat gun to ensure the connection is completely waterproof if you’d like. These are easy to find at electrical supply stores.
  1. Repeat steps 3-5 with the other end of the new wire.
  1. Test the new connection by plugging the wire back into the terminal and testing with the collar to make sure it works.
  2. Rebury the wire.

If your yard is small and you don’t want to mess with finding the break, you can opt to run a new wire after you’ve confirmed that the transmitter and collar are working fine.

Final Thoughts

A buried fence wire rarely breaks because it’s protected from yard tools and vehicles.

However, if you’ve been digging in the yard, you may suspect the fence got broken.

In this case, it’s easy to determine where the break has occurred and splice in a new length of wire.

While the steps to diagnose and fix buried wire sound complicated, most people have their fences back up and running in less than an hour.

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Jesse Hopping, CCDT

Jesse is a natural-born dog-lover certified dog trainer (CCDT), dog foster, and former volunteer at Richmond SPCA and surrounding dog shelters for over 10 years. Her pack includes a Bernedoodle and 3 Boston Terriers. She’s sipping caramel coffee and watching her pack play in the sun when she’s not writing blogs. Jesse has her Certified Dog Trainer designation from CATCH Canine Trainers Academy since 2018 and and majored in English from the University of Virginia.

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