Top Reasons Your Bluetooth Won't Pair

Although Bluetooth may not have originally been intended for use in your car, the technology has earned a place in many dashboards, and as head units ship with native Bluetooth functionality in ever-increasing numbers, the problem of failed Bluetooth pairings is something that more and more people are going to have to deal with on a daily basis.

Whether you’re dealing with a situation where your phone refuses to pair with your head unit, or a Bluetooth earpiece is suddenly no longer paired to your phone, there are a number of issues that may be at fault, from compatibility to interference, and suddenly this “universal connector” can seem to be significantly less than universal. If you’re dealing with pairing or connection problems in your car, here are six of the most common reasons that your Bluetooth device might fail to pair:

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Are the Devices Compatible?

bluetooth compatibility
This is one case where opposites don't attract. Eric Raptosh Photography / Blend Images / Getty

If you’ve never paired this particular headset and phone, or phone and head unit, or phone and Bluetooth car kit, then you’ll want to start by making sure that the devices are actually compatible. Bluetooth is supposed to be cross-compatible in most circumstances, but you can run into situations where devices that employ different versions of the standard won’t work with each other.

Newer versions of Bluetooth, like the current-gen 4.1, are designed to work with all older versions of Bluetooth. So if your brand new phone has 4.1, while your head unit has 2.1—which isn’t terribly unlikely, considering the fact that phones tend to ride the bleeding edge of the technology wave, while head units dog paddle around the kiddie pool—they should pair just fine. The main exception is when one device uses something called “Bluetooth Smart,” since these devices can only pair with devices that are Bluetooth Smart compatible.

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Proximity Matters When Pairing

Bluetooth devices will typically remain paired, although with increasingly poor functionality, at distances of about 30 feet, depending on obstructions. They tend to work better when closer together, and with less obstructions between them, but proximity is particularly important when it comes to pairing. So if your phone is failing to pair with your head unit, and you have it stashed away somewhere, you can try pulling it out and placing it in close proximity to your head unit.

Once your phone has successfully paired with the head unit, car kit, or whatever else you’re trying to connect it to, you’ll typically be able to put it in your pocket, purse, briefcase, or wherever else you want to store it. Or you can stick it in a dash-mounted holder for easy access and cut off future pairing woes at the pass.

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Make Sure the Devices Are Ready to Pair

Pairing a phone with a head unit, earpiece, or car kit is typically pretty easy, but the exact process can vary from one situation to another. If you’re pairing a phone to a car kit or earpiece, for instance, you typically have to make sure that the phone’s Bluetooth radio is on and that the accessory device is in pairing mode. In most cases, with devices that have a single multi-function button, this involves powering the device down and then powering it on with a “long press” until it enters pairing mode. If the device has a single power/operation/charging light, it will typically flash blue and red when it is in this mode.

When pairing a phone to a head unit, you typically have to make one or both of them discoverable, depending on how each one is set up. If your devices are set as discoverable, and you still can’t see one device from the other, then you may be dealing with one of the weird Bluetooth compatibility issues that crop up from time to time.

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Charge it Up

As you may have noticed, if you’ve used Bluetooth on your phone before, the Bluetooth radio can suck up a lot of juice—and cut down on your operational battery life—when it’s active. With that in mind, some phones and other devices are designed to enter a power-saving mode when battery life is low, which will shut off the Bluetooth radio.

You may be able to simply turn Bluetooth back on manually to get around this, or you may find that charging one or both of your devices is the only way to get them to pair correctly.

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Remove Potential Sources of Interference

We live our lives in a soup of digital and analog noise, and it’s pretty common for useful signals to bleed over and become annoying interference. Since Bluetooth operates in an unlicensed part of the radio spectrum, interference from a variety of devices—some of which don’t even transmit anything wirelessly in the first place—is actually pretty common. So if you’re having problems pairing your phone in your car, the solution may be as simple as driving away from the source of interference—unless the interference is coming from inside the car.

Some common sources of interference that can adversely affect Bluetooth pairing include:

  • Wi-Fi
    Although you’re more likely to run into Wi-Fi interference in your home or office, an overly crowded series of Wi-Fi networks in the area can hit you in your car as well. Of course, interference from the Wi-Fi network created by a mobile hotspot can also cause problems. If you use a mobile hotspot in your car, and you’re having trouble pairing, try switching the hotspot off. You should be able to turn it back on without any issue once the devices have paired.

  • USB 3.0
    It may sound strange, but wired USB 3.0 connections can actually spit out interference in the same 2.4ghz spectrum used by Bluetooth devices. The issue is related to poor shielding, and you’re obviously more likely to run into this problem in your home or office than your car, at least until USB 3.0 finds its way into more head units. Of course, if your laptop is sitting on the passenger seat, and it has USB 3.0, then you might want to look at it as a potential source of interference.

  • Other radio spectrum signals
    Essentially any electronic device that bleeds interference into the 2.4ghz spectrum can interfere with the pairing and operation of Bluetooth devices, so you’re likely to run into a whole lot of different sources of interference in your car.

    If the sources are external, you can try to pair your devices at home if you have problems at the office, or vice versa, and if the source is internal, then you may want to try pairing with the vehicle off, or with accessories like inverters unplugged.

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Did You Try Turning It off and Back on Again?

Of course you tried turning it off and back on again. But just in case you didn’t, you may just want to give it a shot. In this case, you may not even have to turn the devices off—turning Bluetooth off on both devices, and then back on, will often allow them to discover each other.

In some cases, where a previously-paired device is failing to pair, removing the device from your phone or head unit’s list of connections altogether will even do the trick. In these cases, you’ll have to remove the device, then set it to discoverable, and voila—no more pairing problems.