Recently I went into my garage to find the invisible dog fence transmitter beeping. After calling the company I was informed that this alarm meant there was a break in the fence, and that I should have them come out as soon as possible - because my dog would surely figure this out in a few days. And hey, for only $100 an hour, they would be happy to help! Long story short, they tried for an hour then told me the yard was too overgrown (half the yard is wooded) and they would have to come back in the fall when everything died back (2 months away). This made me swear that I would do it myself - but after digging up over 100 feet of wire and driving myself crazy for a few days, I had not found the break. Then I found this strategy on the internet (link) that cost me under $20 and worked like a charm. Hopefully this makes it clear for everyone else and saves you some money and frustration. Good luck!
Step 1: Verify the Break
First thing to do is make sure that you do indeed have a break. There are a few ways to do this. On my unit, two wires run from the transmitter to the perimeter fence. Disconnect these wires from the transmitter and put the ends of a paper clip or small piece of wire into the jacks where the wires had been connected. If the alarm is silenced, the transmitter is working properly and you have a break. Another way to verify that there is a break is to use an ohmmeter and check the resistance on the disconnected wires. If there is no resistance the wires are continuous and there is not a break, meaning you may have a problem with the transmitter itself.
Step 2: Materials
To start, you'll need to round up a handheld AM radio and a RF choke (Radioshack part number 273-102).
Step 3: Connect the Choke
Take the two wires that you disconnected from the transmitter and connect them to the leads of the RF choke. Then insert the leads of the choke into the jacks on the transmitter where the wires were originally connected. As I understand it, this allows the transmitter to continue sending a signal to the fence even though it is broken.
Step 4: Tune In
The fence emits a radio signal that is picked up by a reciever on your dog's collar when it gets in range, causing a warning signal or an electric shock. You should be able to detect this signal in the lower AM range. The signal of my fence was roughly 600 kHz. When tuned to the right frequency, you will hear the signal as you pass the radio over the ground. It may be necessary to turn up the intensity of the signal at the tranmitter, although I didn't have to (there should be a numbered dial somewhere on the transmitter, just remember to turn it back down later so you don't fry fido!)
Step 5: Find the Break
Step 6: Dig It
When you've located the area where you suspect the break to be you'll need to expose the wire. I used a 3-pronged hand tiller and dragged it perpendicular to the wire, the invisible fence guys used a pick axe. Use whatever you like but be careful that you don't cut or knick the wire in the process.
Step 7: Check the Break
Once you've found a break, use the radio to check that you have a strong signal on both lines. I actually had two breaks but didn't know it until I found the first break and realized that one of the ends did not have a signal. I continued to dig in the direction of the dead line and found a second break a few feet away. If you have a strong signal on both ends connect them with a piece of wire, disconnect the choke and reconnect the wires from the fence into the transmitter. If the alarm goes off, congratulations, you've found your break!
Step 8: Mending the Break
The final step is connecting the broken ends in a way that is weatherproof and secure. I bought these connectors from the local hardware store, time will tell if they are the best ones or not but you want something that is waterproof and suitable for the temperature range in your climate. This type of connector is filled with silicone to seal the twisted wires. Once you're sure the fence is operating correctly, bury the mended wires and you're done! Good luck!