How To Check Continuity In A Long Wire (Quickly & Easily!)
Doing your own electrician work means that you will have to make sure that the wires you’re installing have continuity. This isn’t always easy to do. A non-continuous wire is usually the cause of a non-functioning circuit, a sudden power outage, or other problems in your grid. With short lines, it’s a cinch. Long lines? Not so much…
To check continuity in a long wire, follow the steps below:
- Disconnect both ends of the long wire.
- Get a multimeter and set it to the lowest resistance with a tone.
- Put a meter lead on either end of the wire.
- If the multimeter emits a tone and has almost no resistance, you have a continuous wire.
Testing your wires’ continuity is a must if you want to be able to troubleshoot most major electrical problems. Understanding the how’s and why’s of this testing method can help you ensure that you will get the best possible results.
Why Do You Need A Multimeter To Check Continuity In A Wire?
Sometimes, you don’t. If you have a really short wire, you can usually check continuity by looking at it and giving it a try with a small circuit on another board. However, when you’re working with very long wires, a multimeter is the only tool that you can use to make sure that the wire that you have is continuous. There are several reasons for this:
- Unlike very short wires, you can’t always see the full span of the wiring. Sometimes, you may need to check the continuity of a wire that runs from your kitchen to your living room. The majority of that wire will be obscured by walls, so you won’t be able to make a visual inspection to see if it’s been frayed or not.
- You can have a break in the wire inside the wire’s casing. There is a common misconception that you have to have the exterior of the wire frayed in order for a break in a wire to exist. This isn’t true. Sometimes, the exterior casing of the wire stays intact but the wire snaps in two due to bad quality or corrosion.
- It’s a fast procedure. It can be intimidating to use a multimeter the first time, but once you get the hang of it, it’ll take a couple of minutes to do a longer wire at most. The learning curve is pretty steep on this, so after a little finagling, you can expect to get the hang of it.
- A multimeter can help diagnose wiring issues that otherwise might be hard to diagnose. You can tell a lot from a multimeter reading. Is your wire truly continuous? Is it frayed and losing its structure? A multimeter can tell you that.
Reading Your Multimeter Results
In a continuous, healthy wire reading, you’ll get almost no resistance and you’ll also hear a beep come from your multimeter. If you hear a beep but see more resistance, you may have a wire that was shorted, mildly frayed, and barely hanging onto its continuity. On the other hand, if you don’t hear a beep at all, your wire no longer has continuity. Somewhere in the mix, it broke.
When a wire has 0 resistance, that means that your wire is an entirely closed circuit. This means there’s no place where there is an open side where electricity could just be losing its power and no open ends.
What Does Resistance Mean On A Multimeter?
Resistance on a multimeter indicates how much friction the electricity has to deal with while it’s traveling through the wire. The best possible resistance reading you can have is 0 ohms. 0 is what happens when you touch two ends of a wire together. Good wire connections all have a resistance under 0.5 ohms, with most circuits showing a fraction of an ohm.
If you get a multimeter of 200 or infinity (depending on the reader), then you have an open-end somewhere in your wire. This means it’s not continuous, and that there’s a break somewhere.
What Can You Do If A Wire Loses Its Continuity?
A wire that loses its continuity will not do much for you. In fact, it won’t do anything. It’s a dead wire. It has ceased to be and is currently pining for the fjords. Since the wire is broken, you need to do one of two things:
- You can patch it up with some extra wire. If you’re comfortable cutting wire, using electrical tape, and sourcing where a specific break happens to be, patching up the wire makes a lot of sense. However, this tends to be a labor-intensive issue that might end up being ineffective, since breaks can happen in more than one place.
- You can also choose to replace the wire. Replacing the wire is the most reliable way to ensure that you get a fully continuous connection. While it may be a little more pricey, it can often be less labor-intensive depending on the quality of the wire.
Do All Wires Have Resistance?
All wires will have a little bit of resistance, simply because the electricity is traveling through a medium rather than air. In most cases, the resistance that you get from the wiring or circuitry is going to be negligible. After all, conductors are made to send electricity to various places with little to no resistance.
What Factors Impact Your Wires’ Resistance?
Wondering why your multimeter has a funky reading? Wondering why it’s a little off? There are several factors that impact how much resistance you can expect to have from your wiring. These below are the most common reasons you might see a number other than 0 on that multimeter.
- The biggest issue, of course, is the material the wires are made of. Some materials are more likely to cause resistance than others. This was especially true with older wires that might have impurities.
- Speaking of impurities, the quality of the wire will also come into play. When we say this, we mean things like making sure that the wire isn’t corroded, noticing if there is visible rust or patina on the wire if it’s been exposed to air, and also making sure that rats aren’t chowing down on your stuff.
- The length of the wiring will also play a major factor. Longer wire means that you will have to deal with more resistance, while shorter wires will accrue less resistance.
- The final factor that can impact how much resistance you have in a wire is the wire’s thickness. Very thick wires tend to have a higher resistance, simply because the electricity has to move more to get to the final destination.
What Should You Do If Multiple Wires Lost Their Continuity?
Let’s say that you’ve been testing a bunch of wires running throughout your home, only to notice that several of them have lost their continuity. This should be cause for alarm, because there is a good chance that there is something that deserves a home inspection. In many cases, this is a sign of your home’s structure being affected by mold, caustic chemicals, or rats on a chewing bender.
Of course, not all homes will be suffering from an undiagnosed mouse infestation when multiple wires are failing. In many cases, what you’re seeing is the byproduct of a home that has aged wires. This is especially true if you haven’t rewired your house in over 20 years. In this case, you might want to look into the cost of having a home rewired.
Can you test continuity in a live wire?
Here’s the thing about this question: just because you can, doesn’t mean that you should. There are methods you can use to check if a live wire is continuous, but that doesn’t mean it’s a good idea. For safety’s sake and for the sake of ease of use, we strongly suggest checking continuity in wires only after you have shut off power to said wire.
How do you know if a wire is bad in your home?
There are several telltale clues. If your wires are well-connected but you get no power to a specific outlet, chances are that you have a bad wire. On a similar note, if you notice that your home keeps having breaker trips when you plug items into a certain outlet, this could be a sign that you need to examine the wiring in your home.If the wiring went bad due to a short, you might have heard a crackling or smelled something burning behind the walls. You might also notice that the wires no longer work. In more extreme cases, a bad wire caused by a short could also cause a small fire or a plume of smoke to come out of the plug.
Why do wires go bad?
A wire goes bad for a multitude of reasons. Sometimes, it’s because of the age of the wires. Other times, it’s a short circuit or a flood that may have damaged the wiring. Even more times, it’s fraying. It’s never easy to pinpoint what happens.
Ossiana Tepfenhart is an expert writer, focusing on interior design and general home tips. Writing is her life, and it's what she does best. Her interests include art and real estate investments.
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