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Swapping Out Bose Head Unit For Aftermarket

28 posts in this topic

This is a little "how to" is dedicated to swapping out a bose Head Unit in a 1998+ Mazda 626, while keeping factory amp and speakers. This method yields to no distortion and excellent sound quality.


Only FAQ incomplete at this time.
_______________________________________________
-Part 1- What you Will need:
SCOSCHE MA02B (buy.com)
SCOSCHE FAI-3A (Can be found at your neighborhood walmart . . . Like any walmart.) [A Line Level Converter or LLC]
If you order it from wally world I think they will send you a FAI-3A not a FAI-3.
Electrical tape. (Your should have this, but your local radioshack/hardware store will have it if you don't)
Standard Wire insulator remover/Multi-tool. (any hardware store you will need 16 or 18 gauge on their)

Or you can go with the Crutchfield kit, but it is more expensive.

________________________________________________
-Part 2- What the materials you need do:
The Wiring harness is to convert the factory wiring to standard after market wire coloring, while also allowing the installer to do little to no splicing for an after market stereo install.
The Line Level converter(will call LLC in this article) converts the signal from 4ohm to 2 ohm for use wit Premium Bose, and JBL systems.
Electrical tape is to cap off unneeded wires and cover exposed connected wires.
Wire insulator remover multi tool is for cutting one wire off factory connector, and also cutting off insulation from your new factory stereo wires.

________________________________________________
-Part 3- Review + Print the below wiring diagram:

Wiring Diagram provided by Xenomorph1030

img-256378-1-bose_wire.jpg

A.......+12 Volt Ignition Wire
B.......+12 Volt Constant
C.......Postive Dimmer
D.......not used
E.......Power Antenna Turn On
F.......Illumination
G.......not used
H.......Remote Amp Turn On
I.......Left Front Speaker (+)
J.......Right Front Speaker (+)
K.......Left Front Speaker (-)
L.......Right Front Speaker (-)
M.......Left Rear Speaker (+)
N.......not used
O.......Left Rear Speaker (-)
P.......not used
Q.......Right Rear Speaker (+)
R.......Right Rear Speaker (-)
S.......not used
T.......not used


________________________________________________
-Part 4- Recommendation before attempting installation:

-Do as much as you can at a desk, working inside the car is more difficult and frustrates easier. Install what you can at a well lite desk if possible.
Installation:
1. Connect the wiring harness to the SCOSCHE LLC.
Follow the diagram below
2. Connect the new after market wiring to the SCOSHE LLC.
3. Set all dials on the SCOSHE LLC to (-)
4. Move Side switch on LLC to factory amp mode.
5. Ground SCOSCHE LLC (easiest way I found to do it was to connect it to the stereo ground and ground them both together to the metal frame inside the stereo compartment.
6. Wire up the non speaker wires from your harness to your stereo please match them all carefully following your after market stereo diagram and the above wiring diagram for the Mazda connector.
7. Cut wire H on the factory mazda harness and extend it with a length of copper wire to connect it to your after market Remote Amp turn on lead(usually blue w/ white stripe)
8. Double check everything and turn it on.
9. Try to run a CD if no sound comes out attempt adjusting factory amp gain on LLC, I personally was able to set all mine to max, but just a warning they dramatically adjust sound levels and each stereo will handle them differently. If you are not careful when you adjust them you could blow your speakers! Also keep all dials at same angles when adjust them.
10. It should work if it doesn't see FAQ/Troubleshooting in Part 5.

________________________________________________
-Part 5- FAQ:
I have no sound?
Check your grounds. Did you remember to purchase and install the LLC recommended at the beginning. And Lastly, did you follow step 7 in Part 4 ?


Some people report that even with the above wiring harness and Line Level Converter you won't get any sound. This is because the MAO2B wiring harness does not pass the Remote Amp Turn on line trough it, you will have to cut tis line, add an extension wire and plug it into your new after market amp. On your new after market stereo you will be connecting it to is blue/white stripe wire.
Now even with the MAO2B wiring harness you will have to cut wire H from before the original Mazda factory connector. This wire is gray (or gray/black will have to check).

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So if i connected these wires off the harness of my new head deck to these wires , labelled a b , c etc using crimps in theory this should providing i insulate them.

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Is this completed.. I know it says it isn't but.. yeah.

Right now I just connected my Scosche harness/Head unit harness to the factory connectors.. but I'm not getting any sound. I didn't cut *any* wires. Any suggestions?

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The instructions are complete but the FAQ isnt thats all.

Did you get the LLC? And did you "7. Cut wire H on the factory mazda harness and extend it with a length of copper wire to connect it to your after market Remote Amp turn on lead(usually blue w/ white stripe)"

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I had missed the step about cutting the remote amp wire. My bad! All worked well after that.. not using an LLC.. but I don't notice any noise or difference in sound quality, to be honest.

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great I'm glad it worked out for you! Did you notice a pretty big improvement in sound quality after doing the swap? Cause I sure did.

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great I'm glad it worked out for you! Did you notice a pretty big improvement in sound quality after doing the swap? Cause I sure did.

It worked out great for me! Sounds incredible, except it has only been a week or so and my front right speaker is busting. I hear it beginning to frazzle out. Looks like I'm gonna have to take my system to the next step and replace speakers and rewire... :unsure:

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great I'm glad it worked out for you! Did you notice a pretty big improvement in sound quality after doing the swap? Cause I sure did.

except it has only been a week or so and my front right speaker is busting. I hear it beginning to frazzle out. Looks like I'm gonna have to take my system to the next step and replace speakers and rewire... :unsure:

Ok, I was wrong. The frazzle sound was actually the way my mp3's were recorded. Will hold off on new speakers :smile:

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so if i just cut the H wire and connect it to the remote amp turn on lead on the aftermarket radio, itll work without buying the LLC?

and do i have to run any wires to or from the factory amp if i do have to use the LLC ??

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Nope youll need the LLC, its not too expensive to grab one. You connect the stock harness to the wiring harness then that up to the LLC. The aftermarket wiring harness does not carry over the H wire, so you need to cut that before the connector on the stock wiring harness. Does all that make sense?

Let me know if you have any other questions.

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Whats the LLC do? My HU was installed the difficult way I think. We just pulled out the Bose HU and chopped the car connector off. Chopped the connector off the new HU and crimped all the wires using the car and the new HU wiring diagrams :lol: . Took forever, but works, sounds good and I didn't use a LLC. I'm pretty sure this voided any warrenty on the new HU, but its worked great and has lived well past the 1 year warranty it did have. Getting the HU to lock into place takes some time and patience, do to all the wire crimps behind it.

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yea, thats def the way not to do it correctly. lol. when a line converter is less then $20. there's no reason to destroy a good wiring harness. if you sold that car, the next owners will have zero clue whats what. when a LLC just unplugs, and is 100% back to stock.

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What's the LLC do though? When I do eventually sell the car, who ever buys it will get all the extra bits. I'm pretty sure I still have both the car's and HU wire harness. They can always redo it the proper way if they want. With the car and HU's wiring diagrams its not that hard to figure out. They can make sure we got the speaker polarity right while they are at it. Our diagram for the car didn't say which one was + or -. We had a 50% chance though. lol.

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So i decided to do this to a friends car. Everything works great. Awesome write-up. The only problem we have is the fact that after we installed the new head unit. the gauge cluster lights and the hvac control lights dont work. any ideas?

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Instead of buying an LLC, can't I just wire up some RCAs to the aftermarket OEM style harness and use my head unit's preout level outputs?

Is the Bose system just looking for preamp signal?

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Iv replaced the radio and did the amp the way you said and the speakers work great. but im still having problems with the power. if i hook the 2 red together with the yellow from radio it turns on. but if i try and hook it up right, yellow to yellow, red to red, it wont even come on. help please?!?!?!! thank you

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Instead of buying an LLC, can't I just wire up some RCAs to the aftermarket OEM style harness and use my head unit's preout level outputs?

Is the Bose system just looking for preamp signal?

Not 100% sure, I've never used RCA's to wire a car. But i do know that the wires to the speakers are also the issue not just the amp, because they are special bose resistance low ohm wires, so no guarantees that work around will work unless you tear out stock wiring.

Iv replaced the radio and did the amp the way you said and the speakers work great. but im still having problems with the power. if i hook the 2 red together with the yellow from radio it turns on. but if i try and hook it up right, yellow to yellow, red to red, it wont even come on. help please?!?!?!! thank you

See answer here: http://mazda626.net/topic/40793-98-mazda-626-aftermarket-radio/

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yea. id just run all new speaker wires to the speakers. and not even bother with the stock stuff. i did that even in my non bose equipped 626 and wasnt hard at all.

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yea. id just run all new speaker wires to the speakers. and not even bother with the stock stuff. i did that even in my non bose equipped 626 and wasnt hard at all.

Agreed rerunning wires is much better, but if you want to do it quicker/easier LLC is the way to go.

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Unless your head unit requires RCA I would just hardwire everything. RCA's don't clip in so they could come loose.

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i dont have sound but havent tryed what you said with the H wire but i also had to replace the front spearkers and they work with the old stereo in if they work with the old one do you think is will work with the new one?

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Welcome to the forum!

And yeah the new speakers definitely should,

the H wire is an absolute must , or else the factory amp wont turn on, and you'll have no sound.

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I want to give my biggest props ever to you for making this thread. I've been trying to figure out how to get sound to my new aftermarket JVC for the past two days and double and triple checked wiring and fuses and search countless hours on the internet trying to come up with the solution. Sure enough, there was no connection on the back of my harness for the "H" plug. Thank you so much. It worked like a charm and sounds 10x better than my factory. I had no choice but to change the factory because the volume knob was messed up and I'd have to fight with it to even try to get sound and at max 3 bars of sound that would fluctuate.

I don't have the money on me to buy the LLC but it worked well enough for me. May consider that later.

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