How To Find And Repair Perimeter Wire Of Your Robot Mower

I’ve got to admit, a break in the perimeter wire of your robot lawn mower can be frustrating.

It’s happened to me a few times over the years. Thankfully, I’ve picked up some awesome tips which make finding and repairing a damaged perimeter wire really easy, and actually a bit of fun!

Although the perimeter wire for robotic lawn mowers is fairly robust, it is not immune to damage. Breaks in the loop wire are usually the result of unintentional physical damage to the wire such as when gardening. In countries with ground frost, sharp stones that move in the ground due to freeze-thaw conditions can damage the wire, particularly if the wire has been stretched excessively during installation.

It is possible for the mower itself to damage the wire if not installed properly, or for pets or burrowing animals such as rabbits and moles to damage the boundary wire.

Thankfully, breaks in the boundary wire do not happen very often, but is an issue that really concerned me when I first installed my robot lawn mower, as I thought it could result in me having to rip up large sections to boundary wire to find and repair the fault.

The good news: There’s a few simple techniques that can be used to help you to find a break in the perimeter wire and easily repair it. I am going to explain how to make finding the break and repairing the wire a pain free process.

What To Do First

If you discover that your mower is not working and realize that the perimeter wire signal is the problem, the first thing you should do is to check that the boundary wire connections to the charging station. It is possible that one of these has come loose or has been damaged. Once you have tried this, check to see if this has solved the problem.  

The next step, regardless of whether you have chosen to bury the boundary wire or simply peg it to the grass, is to walk around the perimeter of the grass, looking for any sign of exposed wire, or disturbance to the grass or soil, which may have led to damage to the wire.

I had one early break in my boundary wire at a time when I had the wire pegged to the ground. I had set the boundary wire too close to a flower bed and the mower toppled into the flower bed. This tilted the cutting blades, which came into contact with the ground and the boundary wire, resulting in a break.

Thankfully on this occasion, the wire was recently installed, the grass had not yet grown over the top of it, and locating the break was easily done as two ends of broken wire were poking up out of the ground.

However, if you have done a loop of your garden and cannot locate a break, what do you do next. Is this the time to start digging, or pulling wire up, starting at the charging station.

The short answer is no! There are a few options to help you find the broken wire, but I am going to tell you about the best one first.

Option One – The Easy Way – This Method Isn’t In Any Robot Lawn Mower Manual!

I was amazed to discover that you can use a portable AM radio to locate the location of a break in the perimeter wire. The reason for this is that a functioning perimeter wire will cause short range interference to an AM radio signal, so you can literally walk around your garden, with a portable AM radio and follow the sound of the interference until it stops, locating the break. If you don’t have one, you can pick one up on amazon for next to nothing. 

AM radio to locate break in perimeter wire my robot lawnmower

The steps involved in this are as follows;

1. Tune an AM radio to approximately 700khz, ensuring that there is no station tuned to this frequency, only static.

2. Disconnect one end of the boundary wire from the charging station, so there is only current running through one end of it. This will mean that the part of the wire after the break will produce no interference, but the part of the wire before the break will make a repetitive beeping.

3. Follow the path of the boundary wire around the perimeter of your lawn, listening carefully for the AM radio interference signal. When you move away from the wire, the signal will fade or stop. This will help you to stay directly over where the perimeter wire is.

4. Once you reach the point of the break, the signal will fade and stop very quickly, which will enable you to pinpoint the position of the break. If the perimeter wire is pegged to the ground, it will simply be a matter of digging down with your fingers until you find the wire and locate the break. If the wire is buried, you will then only have to dig a small section of grass to locate the broken wire.

Option 2 – The Manufacturer’s Recommended Method

This is the option recommended by most manufacturers. If is more complicated and time consuming, but will work well.

The first step is to switch the connections between the guide wire and the boundary wire in the charging station.

This will allow you to see which section of the boundary wire contains the fault.

If on switching the connector for the guide wire and the boundary wire, the error message for the boundary wire is gone, then you know that this section of the boundary wire is intact, and the error must lie in the other section of the boundary wire.

repair broken boundary wire of robot lawn mower

If the suspected boundary wire is short then it is easiest to exchange all of the boundary wire in the identified section. If the fault lies in a long section of boundary wire, then it would potentially take a long time to pull or dig up all of this wire to identify the fault and then peg it down or bury it again.

It wouldn’t be a job I would look forward to.

One way to make this slightly easier is to run a section of boundary wire from the charging station to the mid point of the section of boundary wire where the fault lies.

This will involve using a new piece of boundary wire. You should connect one end to the terminal on the charging station for the section of boundary wire where you have identified the problem. You will need to attach the other end of the wire to the boundary wire at approximately the mid point of the problem section.

To do this, you will need to cut the boundary wire and use a connector to link the new section of wire and the existing boundary wire.

The diagram below is from the manual of my robot lawn mower and explains the idea. Basically, it halves the section of wire where the problem lies.

repair broken boundary wire of robot lawn mower

Once you have connected up this shorter loop, you should check the control panel of the robot mower to see if the error for the missing boundary wire signal has disappeared. If so, you know that the break lies in the other section of wire. If not, then the break lies in the section of wire you are testing. 
You can then repeat this process with the new shorter section of wire that has been identified to have the fault in it.

Obviously, this process is time consuming and involves intentionally cutting your boundary wire at several points.

repair broken boundary wire of robot lawn mower

Fortunately, it is very quick and easy to use the spare connectors, and spares can be purchased cheaply. The connector and exposed boundary wire can be buried, so there will be no visible evidence of the work you have done to the boundary wire. The process for connecting boundary wire with connectors is very simple.

There are some differences between connectors for different manufacturers, but the principle is exactly the same. You just take a new connector and insert the boundary wire in each of the holes in the connector. It does not matter which holes are used for each end of the boundary wire.

Check that the wires are fully inserted into the connector so that the ends are visible through the transparent area on the other side of the connector.

Use a polygrip or a pair of pliers to completely press down the button on the connector.

repair broken boundary wire of robot lawn mower with connector

In my opinion, I feel that the manufacturer recommended method for identifying the break in the boundary wire is excessively complicated and time consuming. I would strongly recommend using the AM radio method. You can purchase a portable AM/FM radio online or in a local shop for almost the same price as a few spare connectors.

After a quick search of Amazon, I found suitable radios for less than £10/$15, which would let me pinpoint the break. Not only would this barely cost more than the official repair method, but it is really quick to do, so the time saving is well worth it in my opinion. There are a number of videos on Youtube which can also show you the exact method for using the AM radio method.

Preventing Breaks In The First Place

Whatever way you look at it, a damaged of broken perimeter wire is annoying, and avoiding it in the first place is by far the more preferable option. You don’t want to be in a situation where your boundary wire is littered with connectors due to repair activity.

Each of these connectors could potentially be a point of failure for your perimeter wire, increasing the risk of perimeter wire problems in the future. There are a few simple measures which you can take to reduce the risk of perimeter wire problems.

Ensure A little Slack Is Left In The Wire When Installing The Wire

If the perimeter wire is under tension when it is installed, or develops tension as a result of movement in the ground over time, it increases the chance of failure at any weak points in the wire.

Sharp stones, or connectors could become points where the wire will fail. Freeze-thaw conditions over the winter can result in quite a lot of movement of stones in the soil, and if one is pressing against the perimeter wire, it can lead to a break over time.

The remedy for this is to leave just a little slack when you are installing the perimeter wire. If you are burying the perimeter wire, this is very simple to do. If you are pegging the wire down, you will still need to ensure that the wire sits flush with the ground, to prevent the mower from cutting a bit of exposed wire, but it will also enable the grass to grow over the top of the wire quicker.

Although you want to leave a little slack, you should not leave a redundant loop or coil of wire along the path of the perimeter wire as this can interfere with the functioning of the mower.

Leave The Cutting Height High At First

After you first install the perimeter wire and get your new mower up and running, the temptation is to set the cutting blades to your desired height and start enjoying a perfectly cut lawn. This is not advisable, as it is very common in the first few weeks of operation for there to be a piece of boundary wire which is sitting up from the grass, or gets pushed up over time by the growing grass.

You should set your mower to the highest cutting setting and slowly reduce the height to the desired level over the space of a few weeks, while periodically walking around the perimeter of the grass to identify any sections of boundary wire which do not remain flush with the ground.

This is more relevant for perimeter wire which is pegged to the ground, but even shallowly buried perimeter wire can sometimes peak up from below the soil in the first few weeks. After a few months, the grass will grow over the top of the perimeter wire and you will not see it at all and should not have any issues.

Ensure You Lay The Perimeter Wire At The Recommended Distance From The Edge Of The Lawn

robot lawn mower perimeter wire distance from edge of lawn

I read the instruction manual of my robot lawn mower carefully before installation, but then thought I knew better, and installed my perimeter wire a little closer to the edge of flower beds in my garden. I did this to try to avoid any strips of grass from being left uncut by the robot lawn mower.

Unfortunately, this led to my mower falling into my flower beds on a regular basis when first installed. As it tilted at a slight angle when getting stuck in the flower beds, it would often result in the cutting blades coming into contact with the ground. There were two occasions when the blades came into contact with my boundary wire.

On one occasion, the wire was cut, and on another occasion, it was slightly damaged, but still worked without issue.

I learned my lesson, and subsequently re-sited the boundary wire at the correct distances from the edge of the lawn.

In fact, I initially pegged my boundary wire down, but following these incidents, I buried the boundary wire. This wasn’t actually that much more time consuming that pegging it down, as I just used an edging tool to create a narrow slit in the grass, in which I inserted the boundary wire.

Thankfully, I have had no issues since. I would strongly recommend following the instructions in the manual of your robot lawn mower exactly, to avoid similar problems.

Ensure You Keep Some Spare Perimeter Wire And Connectors For Your Robot Lawn Mower

robot lawn mower perimeter wire

If the worst should happen, and your perimeter wire gets cut or damaged by something, it is really frustrating to have to wait for a delivery of new perimeter wire or connectors to fix the problem. Most robot lawn mowers come with a small number of spare wire connectors and manufacturers normally provide enough perimeter wire to have a little left over.

There are a few exceptions. If your lawn is a very unusual shape, or has a lot of obstacles within the body of the lawn that need to be marked out, you may need to do a quick check to make sure you have enough wire before you start the installation process.

All the different robot lawn mower manufacturers will provide their own wire and connectors, but often there is no difference between them other than the packaging. Manufacturer branded spares tend to be a lot more expensive than perfectly acceptable generic alternatives.

After I got my current robot lawn mower model, I bought a multi-pack of compatible connectors and spare blades off Amazon and a spare pack of wire. It saved me a lot of money compared to the official spares. This means if I have a break or if I want to move the boundary for my robot lawn mower, then I have plenty of spares to make this an easy process.

What About Getting A Robot Lawn Mower That Doesn’t Need Perimeter Wire?

This would be great, but unfortunately there are no good options yet for robot lawn mowers that don’t require perimeter wire.

The edge detection technology is getting better with every new model that is released, and I’ve no doubt that perimeter wire will be a thing of the past in a few years, but for now, perimeter wire is the best option. I’ve written an article all about robot lawn mowers without perimeter wire here. 

Hopefully you don’t have to worry about boundary wire problems too often when using your robot lawn mower, but if you do, I hope this information has been useful. Let me know in the comments section about your experiences with damaged perimeter wire. If you have any questions about robot lawn mower perimeter wire, I’d be glad to try to answer them.