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Send Nuvi Audio to Sena SMH5 Bluetooth Headset
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Recently I finished a 7,300 mile motorcycle trip down Highway 50 from Ocean City, MD to Sacramento, CA then to Palm Springs, CA and back to Detroit, MI via a southern route using a Garmin Nuvi 1390T GPS for guidance.

This GPS is not intended for outdoor use so I made a weather/glare shield for it and attached the Garmin Nuvi 1390T to my windshield using the factory suction cup mount. For insurance I also attached a bungie cord from the GPS and my handlebar.

NUVI weather/glare shield - MPC Computer Repairs

Through temperatures ranging from 65F in the east to 116F in the west and heavy rains in the east to bone dry weather in the west, on pavement smooth as silk to bone jarring cobblestone chunks of concrete, the Garmin Nuvi 1390T GPS performed, and continues to perform, flawlessly. A testament to the quality of the construction of this piece of 'consumer' electronics.

I did have to reseat the suction cup mount one time in the 7,300 mile trip and that was after going from a very hot desert environment to a very cool mountain environment. The GPS did not fall off the windshield it just took very little pressure to remove it.

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I had installed a Sena SMH5 Bluetooth headset and intercom into my Arai helmet  and paired it up to my smartphone so that I could use it hands-free, but, I could not get the Garmin Nuvi 1390T GPS to pair with the SMH5 so I could hear the voice prompts.

Sena SMH5 motorcycle Bluetooth headset with intercom - MPC Computer RepairsArai fullface helmet with Sena SMH5 Bluetooth headset - MPC Computer Repairs

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The audio volume from the speaker of the Nuvi 1390T was not strong enough to hear with my helmet on let alone when traveling at speed.

 Because I was planning another motorcycle trip, I was in the market for an additional GPS unit I could dedicate to the motorcycle and that is when I discovered that I would have to spend in excess of $600.00 to get a Garmin GPS with Bluetooth Audio Out compatible with my Sena SMH5 headset.

I refused to do so and thus this project to route the Garmin Nuvi audio to my Sena SMH5 Bluetooth headset was born. Actually this modification should work with almost any GPS and Bluetooth headset or a communications / intercom device like the J&M CB radio.

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The Garmin Nuvi 2597LTM GPS
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After extensive research and because I already owned multiple Garmin GPS units I decided on a Factory Refurbished Nuvi 2597LTM (actually it was the price) purchased from http://g.factoryoutletstore.com.

When compared to the Nuvi 1390T, this GPS has a little larger five inch screen, it has 'Voice Command' for voice control and it has the Traffic Information Receiver built into the unit rather than into a rather bulky dual purpose power cable.

Garmin 2597LMT GPS - MPC Computer Repairs

This unit does not have the bluetooth communications ability to talk directly to the Sena SMH5 headset. If you are interested, some of the technical details on Bluetooth communications can be found in PDF format here. You can read the full article at The Headphone List.

Please note that the following modification does not disable or mute the GPS internal speaker, it will continue to operate normally.

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The Anker MB220 Bluetooth Transmitter-Reciever
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Additional research turned up a very neat piece of Bluetooth gear, the Anker MB220 Bluetooth Transmitter and Receiver. As its name suggests this unit will transmit audio fed to it to an other device via Bluetooth or, it will receive audio transmitted to it via Bluetooth and feed it to another audio device. This change in function is controlled by a switch located on the side of the MB220.

Anker MB220 Bluetooth Transmitter and Receiver - MPC Computer Repairs

My plan was to feed the audio from the Garmin Nuvi 2597LMTs speaker into the Anker MB220 and transmit it in the format that the Sena SMH5 Bluetooth headset wants.

Note that Ankor is no longer making the MB220. Doing a search for "Bluetooth transmitter and receiver" turned up a number of different devices that claim to work the same way. Please note that I have not tested them. A simple test would be if it 'Pairs' with your headset it should work.

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Tools Needed
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These are the tools you will need for this project:

    1 - T5 torx bit to remove the screws from the back cover of the GPS. *
    1 - Mar-proof tool to separate the back cover of the GPS.
    1 - #26 drill bit and drill motor to make a small hole in the back cover of the GPS.
    1 - Soldering iron and solder (.028 rosin core).

Tools required for NUVI audio project - MPC Computer Repairs

        * Note: Your GPS may have a different type of screws holding the back on.

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Hardware Needed
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    1 - 3.5mm or 1/8 in. stereo jack with at least 8 inches of matching stereo cable.*
     2 - 4 inch Pieces of 30 AWG wire wrap wire or 28 AWG hook-up wire.
    1 - Two inch long piece of 1/4 heat shrink tubing.
    1 - Two inch long piece of 1/8 heat shrink tubing.
    1 - 47uf 25vdc capacitor.**
    1 - Tube of GOOP sealant or sealant of your preference.

* Note: You need to determine if you are going to mount the Anker MB220 directly on the back of the Garmin Nuvi 2597LMT or at some other location and cut the stereo cable to the length needed.

** May be a different value for your GPS.

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Stereo Cable Preparation
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In the photo below the first cable is the one that came with and Anker MB220 which I felt would not hold up to the rigors of a motorcycle environment so I opted for a heavier (approx. 3/16 inch (0.147 or 3.73mm) ) stereo cable. Note that you need a stereo cable if you want to get sound to both speakers in the headset.

Audio cables for NUVi audio project - MPC Computer Repairs

The second cable is a standard stereo cable that had a jack at both ends. I removed the jack from one end of the cable and bared the wires as shown on the third cable.

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Prepare the end of the stereo cable by striping the Ring and Tip conductors (red and white wires) and joining them together. These wires will be soldered to the hot (+) side of the speaker in the GPS receiver. On the Garmin this was a light blue wire connected to the speaker but it could also be red or some other color.

Cable end preperation for NUVI audio project - MPC Computer Repairs

The stereo cable shielding should be twisted together as shown and some shrink tubing put over it leaving about 1/8 inch of the end exposed. This wire will be soldered to the negative (-) side of the speaker in the GPS receiver. This is normally where a black wire is connected to the speaker.

Using a soldering iron, tin the ends of both wires in preparation for soldering them to the speaker.

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Open up the Gamin Nuvi 2597LMT
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First remove the screws from the back of the Garmin Nuvi 2597LMT using the T5 Torx driver. 

Step 1 - Opening the NUVI 2597LMT - MPC Computer Repairs

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Then, using the mar-proof tool, CAREFULLY seperate the back from the unit. PLEASE do not use a vise to do this procedure. I just used it for a prop to take the picture.

Step 2 - Opening the NUVI 2597LMT - MPC Computer Repairs

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Notice that all of the electronics are in the back cover while the front cover houses the display screen.
Be careful that you do not pull the ribbon cable that connects the display screen to the electronics out of it's connector as it can be problematic getting it back in. It is the gold thing in picture below.

Step 3 - Opening the NUVI 2597LMT - MPC Computer Repairs

That white tag you see on the lower right in the picture is the battery and that round black thing to the left of the battery is the speaker.

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Install The Stereo Cable
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From the INSIDE of the Garmin Nuvi 2597LMT GPS locate a suitable place to drill a hole for the stereo cable to pass through. In this case there was only one place to do this.

The stereo cable I used measured approximately 0.147 (3.73mm) so I chose a #26 drill bit which would make a hole that would allow the cable to easily slip through but not be too big.

To make things easier I inserted the stereo cable into the hole and double checked the length of the wires going to the speaker. In fact I made sure that they were a little bit long.

I also applied the Goop sealant to the cable and the hole and let it dry before soldering the wires so that I would not get fresh sealant all over the inside of the GPS while trying to do the soldering.

I left the GPS open over night to allow the sealant to 'gas off' before soldering the wires to the speaker.

Drill hole for Audio Out cable - MPC Computer Repairs

The next day I routed the wires and trimmed them to fit making note of the tight fit when putting both halves of the GPS back together.

Please note that while I used a 90 degree male stereo jack, a straight male stereo jack or a female stereo jack can be used if you want to connect the GPS to something like a J&M CB radio using their male adaptor cable.

You can even plug your wired headset/earbuds directly into your GPS if you do not want to go the wireless route.

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Coupling Capacitor Installation
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You may not need a coupling capacitor with all GPS units but if you do not install one you may end up with garbled audio after a short time of operation. Better to test and install it while you have the unit apart the first time rather than having to tear it apart again.

In the picture below you can see that the red and white wires of the stereo cable have been soldered to the negative (-) lead of the 470uf 6.3v coupling capacitor for testing. The positive (+) lead of the 470uf 6.3v coupling capacitor has been soldered to the light blue speaker wire.

Setting up coupling capacitor test - MPC Computer Repairs

After testing with capacitors I had on hand, the value of capacitor that proved to work best for me was a 47uf 25vdc which gave decent 'crisp' audio quality, that can be heard above road and wind noise, and good volume from the Sena SMH5 Bluetooth headset. Note that while this value works well for me it may be different for you.

The twisted shield wire of the stereo cable has been covered with black shrink tubing and soldered to the black speaker wire.

Go to the Pairing and Communications Testing section for the procedure to test your audio quality. Note that you only have to perform the 'pairing' procedure once. After that, 'pairing' will be performed on power-up.

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Now to clean up the installation. First you need to find a 47uf 25vdc capacitor (or whatever value you determine works best) that will fit in between the GPS battery and the GPS main board. That is the area where the red and green and black wires are going into in the photo above.

I soldered kynar wire 30awg (wire-wrap wire) to the shortened leads of the capacitor. Red to the Positive (+) lead of the coupling capacitor and white to the negative (-) lead of the capacitor. If you cannot find 30awg kynar wire you can use 28awg hook-up wire.

Preparing coupling capacitor for installation - MPC Computer Repairs

For safety sake slide a piece of shrink tube over the bare leads of the capacitor. Bare the other ends of the kynar wire. Solder the red wire from the coupling capacitor to the speaker pad with the blue wire. 

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Slide a piece of heat shrink tubing over the red and white wires of the stereo cable. Solder the white wire from the coupling capacitor to the red and white wire of the stereo cable. Slide the heat shrink tubing over the solder joint and shrink in place.

Completed coupling capacitor installation - MPC Computer Rrepairs

If you zoom in on the photo of the NUVI 2597LMT above, it will be easier to see the placement of the coupling capacitor in-between the battery and the main board. Try to keep the wiring off of the speaker and the battery or it will be pinched when you put the covers back together. As you can see the wiring layout  and routing is quite simple. Now, for comparison, look at the NUVI 2595LMT below.

If you zoom in on the NUVI 2595LMT you will notice that you will have to grind or cut notches in the internal webbing of the case to get clearance for the wires and the capacitor installation. There is absolutely no spare room in this unit. The NUVI 2599LMT is the same. Route the wiring so that it is not on the battery or the speaker magnet.

Watch how much solder you apply to the speaker pads as too much will cause the speaker to short out against the metal cover for the display. For safety, there is a piece of clear plastic tape placed over the solder joints.

Wait, wait, wait..... don't close the GPS up yet. You can put both halves together but do not snap it shut until you have actually tested it to make sure it works correctly.

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Pairing and Communications Testing
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    NOTE: Please make sure that the Garmin has its Bluetooth setting to 'OFF'. 

    1 - Make sure that the Anker MB220 is fully charged.
    2 - Place the Tx- Rx switch is in the Tx position.
    3 - Plug the stereo cable from the GPS into the Anker MB220s stereo jack.
    4 - Turn on your Sena SMH5 Bluetooth headset.
    5 - Turn on the Anker MB220 and put it in 'Pairing Mode'.
    6 - Perform the 'Pairing' function on the Sena SMH5 Bluetooth headset.
    7 - You should hear a confirmation that it paired with the Anker MB220.
    8 - Turn on the Garmin 2597LMT GPS. Set the volume to at at least 3/4.
    9 - You should hear the startup beep in your headset.
   10 - Perform any step on the GPS to confirm audio in your headset.
   11 - Adjust the volume on the GPS for the clearest audio in your headset.
   12 - Trun off the GPS, snap both halves back together and install the screws removed earlier.

NUVI 2597LMT with Anker Bluetooth transmitter-receiver - MPC Computer Repairs

There are still some options to consider. You can attach the Anker MB220 to the back of the Garmin 2597LMT with double sided tape if you are only going to use the MB220 with that GPS.

You can also attach it with stick on velcro strips so that you can remove the MB220 and use it on other devices you want to send or receive audio, music or video to/from via Bluetooth.

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One More Thing - Your GPS Cradle Mount
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If you are using a 'cradle' mount such as a RAM, it may have to be slightly modified to allow clearance for the stereo cable as the general illustration shows below (zoom in for better detail). Note that there are a number of different brands and styles of cradle mounts and that this is just to illistrate what the slight modification may look like to this particular brand and style. Your's may be different.

If you are using a 'ball' mount such as below, no modifications are necessary to accomodate the cable exit location.

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Total Project Costs
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I purchased a factory refurbished Garmin 2597LMT with one year factory warranty.
I purchased the Anker MB220 Bluetooth Transmitter and Receiver.
I purchased a 6 ft long 3.5mm (1/8 in) stereo cable with jacks.
I used a 47uf 25vdc capacitor from my 'miscellaneous' parts box.
I used a company soldering iron and solder.
I used some company shrink tube.
I used some company sealant.
I made a new weather/glare cover using leftover material.
Total costs = Less than $200.00

If you would like us to modify your GPS please call to schedule a date before shipping it to us.

At m-p-c.com we have been repairing computer hardware, software, virus and network problems since 1984. Call us at 734-697-4514
(Smart Phone users Tap on the number to dial)

Click on the 'Contact' button below for shipping address information.......

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Price to perform the GPS audio modification is $55.00 USD plus insured shipping

That price includes the cost of the stereo cable, the coupling capacitor and labor. It also includes the cost of modifying your cradle mount, if needed. It does not include the cost of shipping.

You will know the cost of insured shipping because we send your unit back in the same packaging you sent it to us. So,whatever it costs you to ship your unit to us, it will cost us to ship it back to you. Just add that to the cost of the modification when you write your check.

You can also pre-pay the cost of return shipping and put the return label in with the GPS and your check for $55.00 USD when you ship it to us.

Please note that if you have damaged the heads of the screws on the back of your GPS and they cannot be removed with a standard torx or philips driver, there will be an additional charge of $35.00 USD to remove and replace them.

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Last Updated 08-04-2017
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