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Discussion Starter · #1 ·
Ok, i tried using the search function but still really confused. I want to put a aftermarket deck in my 98 ML with a Bose System. My stock deck is a single DIN bose deck. Some people say i need a adapter to run it with the bose system, some say i dont need a adapter and all i need is a harness, others say that i have to re-wire the whole car and that i cannot use the bose system. So, what is it. All I want is to change the deck and still use the bose system. Thats it. Please help! Thanks
 

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You can use a harness that is available for VW's I believe. Check Crutchfield for the harness. The only thing is that you have to use a head unit that has front and rear Pre-amp line outs. I soldered RCA plugs into the wires leading to the speakers on the harness. You will also have to use the remote turn on to activate the Bose amp. There is an extra wire in the harness that does this. I did not write it down when I did it and I'm not sure which pin it is. If I ever get a chance I'll have to do that. I used the wiring diagrams I found on this site to tell which wire went were. I mainly did this so I could use the iPod line out into the new head unit's AUX input. I've lost functionality of the changer, but with the iPod I never had CD's in it anyways.
 

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Discussion Starter · #3 ·
So its just not wiring up the harness and plugging it in? I talk to crutchfields techs and the said just wire up the harness to the deck and just plug the harness.
 

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I don't think the Bose amp can handle the high level signal from the amp section of the head unit. That is why you have to use the RCA plugs. That's the only real change from just plugging it in. That is unless the harness from crutchfield has RCA plugs already.
 

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Discussion Starter · #5 ·
No the crutchfield harness is just a harness. Is there any other ways out there?
 

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Use the search function but be sure to only take note of the one's for 98 and 99.

In any case, it's a little more complicated than just plugging into the wiring harness. It depends on what you want to do and what's in your system.

It's difficult to just change the head unit and still retain the BOSE system. You must find an amplifier that can drive a 2ohm load which the BOSE system uses. This can be done by either finding a tape deck, like the one already in the car, that has an amp that works at 2 ohm or you buy an outside amp that works at 2ohms to plug into the BOSE equilizer unit and plug your stereo into the amp (probably using the RCA's) You might tap into the original harness to more easily access the connections or just tap into the wires of the harness behind the connector using commonly available wire taps (or cut out the connector and plug in directly also) The problem is that aftermarket is commonly 8 ohm loads and BOSE is not. Read the links to get more detailed info although it is very technical so prepare yourself.

Here's the link to Ken Yee's site which has all you ever wanted to know about your 98 stereo system.
http://www.keysolutions.com/M-Class.nsf/8178b1c14b1e9b6b8525624f0062fe9f/ad96201628ab6ea685256921000856f8

You can also visit the site for additional information at http://www.keysolutions.com/M-Class.nsf

Lots of people just rip out the BOSE system cause it's easier and honoestly I don't think it's very good myself. The best part about it is the well packaged subwoofer under the drivers seat but even that doesn't go as deep a many aftermarket woofers.

This subject was recently discussed maybe 2 weeks ago so go back a few pages to find it.
Good luck
 

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bigcatny - 2/2/2005 5:05 PM

It's difficult to just change the head unit and still retain the BOSE system. You must find an amplifier that can drive a 2ohm load which the BOSE system uses.
I don't think that's correct. It wasn't difficult at all. The Bose amplifier drives all the speakers in the truck. The signal into the amplifier is just line level, impedance is not an issue. It would be an issue if you were using the head unit to drive the speakers themselves. I have my aftermarket head unit's RCA outs driving the Bose amplifier. Sounds a little better than with the stock head unit, probably because the CD section is better. Sounds much better with the iPod using the AUX in...as opposed to the tape adaptor.
 

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Ok guys, it is not that hard to keep the Bose system in the ML if you want it. Here is what i did.

Bought a scorche VW86 harness
Switched the Constant +v and the switch +v
Remove the cd changer/integrated phone harness (if you have it)
Bought a scorche inline converter that sits between the aftermarket harness and the harness of the unit.

Just calibrate the scorche inline converter til you get good sound out of all speakers and you will be good to go.
 

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ttaleric - 2/2/2005 10:08 PM

Bought a scorche inline converter that sits between the aftermarket harness and the harness of the unit.
It's even easier if you use a head unit with front and rear line outputs...no need for the converter!
 

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lechonlubber - 2/2/2005 9:58 PM

The signal into the amplifier is just line level, impedance is not an issue. It would be an issue if you were using the head unit to drive the speakers themselves. I have my aftermarket head unit's RCA outs driving the Bose amplifier. Sounds a little better than with the stock head unit, probably because the CD section is better. Sounds much better with the iPod using the AUX in...as opposed to the tape adaptor.
I don't know what you plugged into but the input into the BOSE EQ/AMP on the firewall is speaker level. Is it possible that you never play your system very loud? Of course you can put a lower level input into the speaker wires dangling in back of the head unit since the bose is also an amp, it'll just be less loud.

The problem with the ohm thing is amp output. If the amp is not well built then it's not going to get anything near the watt rating of the amp. You may even burn out a bad amp if your trying to play very loud. This is fine for your speakers since they'll never be driven near the output limits but they'll also not be very loud. You may not care or notice.

Besides, by pumping sound through the Bose amp/eq and leaving the original speakers (which I happen to think aren't very high quality) the sound will be the same as if you never swapped the head unit at all. That may be fine for you, it just does not agree with my sense of sound quality. The advantage as pointed out here is that you may gain an auxiliary input for your ipod for instance. If that's all you want and some bling bling in the dash, great for you.

And of course the aux input sounds better than a tape adapter, it's like night and day. TApe adapters are always the next to last option right after FM tansmitters. Tape heads aren't designed to carry the signal range of the aux inputs.

Have you tried plugging the ipod in using the universal adapter at the bottom or are you using the headphone jack. The difference is equally night and day since I'm sure you know the IPOD jack is equalized to cut off the top and bottom end of the signal so as not to overstress headphones. Of course if your using the original bose speakers you probably can't hear the difference as I doubt they are good enough to let you hear the difference. And it sounds as if your system may not be running at high output very often, if ever.

Like I said, if it works for you great. If it works for the guy that started this thread even better. Never worked for me so I ripped it all out and started from scratch. That's great also.
 

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bigcatny - 2/2/2005 11:06 PM

I don't know what you plugged into but the input into the BOSE EQ/AMP on the firewall is speaker level. Is it possible that you never play your system very loud? Of course you can put a lower level input into the speaker wires dangling in back of the head unit since the bose is also an amp, it'll just be less loud.
The RCA line level ouputs of my head unit are driving the inputs on the Bose amplifier. I am not using the amplifier in the head unit. It get's plenty loud...as loud as it got with the stock head unit. If the input stage of the Bose amplifier was speaker level, my setup would not work. Line level is high impedance, speakers are low impedance. If you put a speaker load on a line level output, there would be little or no sound. There would not be enough current to drive the speaker.

I too thought that the stock head unit had an amp that was driving the main speakers. When I pulled it out, I noticed that there were no heat sinks on it. At that point it looked like it was line level. The EE in me decided to test my theory by driving the Bose system with a line level signal. Needless to say, it worked. I soldered up a harness and went with it. It's been in the truck for a few months now with no issues.

Besides, by pumping sound through the Bose amp/eq and leaving the original speakers (which I happen to think aren't very high quality) the sound will be the same as if you never swapped the head unit at all. That may be fine for you, it just does not agree with my sense of sound quality. The advantage as pointed out here is that you may gain an auxiliary input for your ipod for instance. If that's all you want and some bling bling in the dash, great for you.
I understand that SQ with the Bose is not audiophile quality. My previous cars had MB Quart, JL Audio, Alpine, Rockford Fosgate (I miss old school Punch), Soundstream, Nakamichi, Denon and other high end equipment. I know it could sound so much better. But all I wanted was better sound from the iPod. The Bose system is fine for day to day driving...it's much better than the non Bose system. I didn't want to end up with a truck full of equipment. When I want to hear good sound I warm up the rig at home.

Have you tried plugging the ipod in using the universal adapter at the bottom or are you using the headphone jack.
I'm using the Dock connector output. It does sound much better than the headphone jack. I can hear the difference between the two. The system gets plenty loud. I also noticed that CD's sound better, the transport and DAC in the new head unit is much better than the one in the stock changer.

The reason I'm going through all this is to say that replacing the stock head unit on the Bose system is not that hard. A little experimenting, some electrical knowledge and the search function on this board are all that's needed. Any competent installer should be able to figure it out.
 

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interestingly my head unit has a heat sink and ran the speaker level output. There is no RCA output. Mid-model change?
 

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bigcatny - 2/3/2005 11:32 AM

interestingly my head unit has a heat sink and ran the speaker level output. There is no RCA output. Mid-model change?
Mine uses the same speaker lines, it's not an RCA plug. I put RCA plugs onto the "speaker" lines. The base (Non-Bose)stereo has heat sinks, the Bose one did not, just a metal shield. I suppose they could have made a mid-model change.
 
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