Introduction: How to Replace a 12v Cigarette Lighter Socket With a USB Charger Port and Voltmeter

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Video tutorial on how to replace your cigarette lighter or 12v auxiliary port with a USB charging port and voltage meter combo. For this I am using my 2006 Dodge Ram as an example, but I’ll try to keep this generic so it applies to any vehicle. I’ll go over all the important points like determining which port is switched with the ignition and determining polarity.


Step 1: 12v USB Charging Port/Voltmeter Combo

For a regular cab truck, it has 3 of these cigarette lighter/ 12v auxiliary ports, so I thought this would be a great upgrade instead of carrying around an adapter for USB charging and I can keep an eye on the voltage when listening to the radio with the engine off. Not all vehicles are equipped with a live voltage meter on the gauge cluster or there can sometimes be issues with accuracy.

I purchased this online, this version has an aluminum outer body and a link to it will be in the video description. You can get versions without a voltage meter and the same procedure also applies. This version also came with an aluminum polished outer shell, as well as a green and blue display. Mine has a red display. This also came with pigtails and crimp terminals, however, I’ll be using my own instead.

Step 2: Required Trim Removal

In order to install mine, the radio bezel needs to be removed. With this particular truck, it has two screws just above the cup holder, however, mine is missing. Next is using a nylon trim tool to disconnect the clips holding the trim in place. Being that it’s currently cold, be careful with the plastic as it can be brittle.

Once removed, tilt the top down, there will be various wires in behind that needs to be disconnected. Start with the one side and work your way across. Each connector will have a tab that needs to be depressed, then remove. The 12v ports may need a small tool to help depress the tangs.

Step 3: Determining Switched Power Connector & Polarity With a Multimeter

Now to determine which is the switched source. Some 12v ports remain on all the time or they can be switched with the ignition. This can be checked using a multimeter or test light and I’ll demonstrate both examples. First using a multimeter, set it to the two-digit dc voltage setting. Make sure you have the leads in their correct position, this will help determine which wire is positive and negative.

With the key in the off position, test the plugs for the 12v ports. These can be probed from the front or rear, whichever is easiest. As you can see, one has no voltage and the other has voltage present, therefore it’s on all the time.

If you’ve noticed, the value was negative on the meter readout, this means the polarity is mixed up. Therefore positive is negative and negative is positive. So when the leads are switched, the value will be shown as a positive value. Therefore the black lead is on the ground and the red lead is on positive. This will need to be known when connecting the new port.

Next, I have stuck the probes in the back of the connector so they stay in place, then turning on the ignition, the circuit has power right away. Once the key is turned off, the circuit turns off as well.

Step 4: Using a Test Light Instead

Using a test light, this too can determine a switched source, along with the polarity. Instead of hooking up to both wires at the plug, the test light can have the negative wire connected to a known ground source. This can be on another connector, to the battery post, sometimes a body bolt under the dashboard, or a bare metal bracket. It’s best to vary its connection with a reliable power source too such as the battery.

With a known ground source, the light will illuminate when it makes contact with a live power wire. As you can see its powers on the none switched 12v port wire, but won’t on the other when the key is off. When the key is operated on and off, you’ll see the light turn on and off. The wire at the connector being tested is the power wire and the opposite not being tested will be the ground.

Step 5: Installing the Connectors

With the key off, the connector casing can be removed and you may be lucky where the terminals will connect to the new port. Unfortunately, this wasn’t the case here. I also tried sourcing a plug that connects to the factory plug but was unable to find one, so I’ll have to cut the wires instead. Slide the outer retaining frame on the connector forward, there are two tabs on the back that needs to be disconnected. Once forward, this will exposed tangs on the inside of the connection, pull those away from the terminals, then remove the terminals. I’ll provide a close-up in a moment. The test light is a sharp tip that works great for accessing these tangs.

With the connector removed, I just cut off the terminals.

Then strip the insulation so the appropriate length of the conductor is exposed.

Twist the wire strands. Using the correct sized crimp terminals based on the wire gauge, install the terminals on each wire and then crimp. Whenever a crimp connection is done, always give it a pull test to ensure the wire is firmly in place.

Now we’re done here and next is moving onto the bezel. I did a quick test using the new port to ensure it’s working correctly.

Step 6: Removing the Old Port

For the factory 12v port, it has an outer shell that holds it into place. From what I’ve found, the inner frame slides out first, then the outer black shell can be removed. For some reason, mine was jammed in place and I wasn’t able to separate it. The inside of my factory port is rusty, so I won’t bother keeping it anyway. Instead, I just broke off the mounting tabs, the rectangular slots exposed chrome in behind is the tab locations.

As for the plug, the clear outer plastic is what keeps the terminals in place, along with small tangs on the inside. Here you can see one of those tangs, they need to be pulled away from the terminals.

The new port doesn’t fully fit and the hole isn’t completely round. So it does require some sanding, for this will be using a small drum sander on a drill. The finer the grit, the cleaner finish you’ll achieve. It’s only plastic so the material can be removed quickly.

Step 7: Fitting the New Port

First was sanding out the flat side, then test fit the new port along the way, making sure it’s the correct size. Take your time, don’t cause any damage to the bezel. This can also be done by hand, using sandpaper wrapped around a dowel, or even using a small rotary tool.

After a couple of minutes, the hole in the correct size. Some plastic fibers or hairs may end up around the hole and this can be typically cleaned up by rubbing your finger around the edge.

Step 8: Installing the New Port

Install the new port, if equipped make sure the rubber cover is aligned properly with the new port. This rubber cover will keep the port looking clean and provide protection from any dust or dirt.

Install the large nut on the rear.

To snug up the nut, it may be hard by hand so interlocking pliers can be used. With the nut only being plastic, it can be damaged easier, so I would recommend wrapping electrical tape around the jaws. Don’t over tighten it, it’s only plastic. You just want it tight enough where it won’t move or come loose over time. Then verify that it’s straight, if not, make adjustments as needed.

Step 9: Reinstalling the Trim Bezel

Finally, the bezel can be installed back into the truck. Plug in the rest of the connectors, I find starting from one side and working your way across is best. A test run can be done to ensure it’s working correctly. The new port does have the terminals marked with a positive and negative, so make sure you have the correct wires in their position.

Snap the trim back into place and reinstall any fasteners if required.

Step 10: All Done!

Once done, here you can see it’s operation. The rubber cover does have a tinted transparent window so the voltage can be viewed while the USB ports are protected. Depending on your vehicle’s design, makes sure you do take measurements on the port you’re considering purchasing to ensure it fits.

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