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1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #1
Hi there,

I’m planning to install a power amp and a new speaker sets and would like to ask for some tips and tricks for pulling cables from the headunit to the trunk.
Mine is a 1994 SL320 with a non-Bose system. It came with a stock radio and front speakers on the doors and dash only. I have replaced the stock radio by a Pioneer DEH-4150SD head unit 2 months ago.
I found the speaker surrounds were all gone when I replaced the door catch so I decided to replace the speakers. I have also decided to install an amp to drive the front speakers and the amp will be bolted in the trunk as I want to keep the rear seats.
I decided to investigate how to do the wiring from the head unit to the trunk last night. I examined my car with the rear seat cushion removed and the only route I could find was to have the cables running under the center console and armrest where it can reach the backseat but I was stucked there. I guess it may be possible to have the cables reach the trunk through the side panel but I had no idea how to open it. I could only see 2 cross screws with a black plastic cap covered. Can anyone tell me how to open it without damaging the panel? I also wonder if the routing is correct or not. Will it be easy to interrupt the hydraulic system at both sides? Some of my friends also told me it may have some annoying distortion if I run both signaling cables and speaker wires together. Should I run them separate to the trunk? I feel it’s tough enough for running the wires to the trunk and even may need 2 separate routes.
I’ve tried to search for some DIY videos or photos for running cables but no luck. Can anyone give me some useful advice? Many thanks.

Anthony:D
 

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07 SL350, 14 BMW320, 05 SLK and 4.6 MGBV8
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745 Posts
It is possible. But messy!

You must remove the rear seats and boxes. The locator screws are quite obvious. Be careful to remove the vacuum lines to the box locks - they have slide clips holding them in, you will see clearly how they come off.

Now remove the plastic trunking running alongside (the drivers side on a RHD - passenger side on a LHD) that has all the wires in it. The lid of this trunking is held in by built in clips - you will see how they function on a close look.

Then, take off the rear well trim panel. This is the messy bit. I have done it so many times now that I can get away with pulling one side away and finding the access hole by feel.

Now, if you follow the wiring up the side of the rear well, you will eventually find where it enters the boot. Now you have to pull out all the trim in the boot (trunk) to find the route over to where you want the amp to fit.

hth.
 

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Registered
1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #3
Thanks a lot, Hal.
I hope you won't mind to give me some more details...you have mentioned about removing the boxes. Did you mean the parts behind the shift knob like the cassette holder, armrest and the storage? Also the plastic trunking, was that the part right beside the chrome door step panel or it is something else that I will see after removing the center console (boxes if my guess is correct)?

I saw a few cables coming out from the bottom of the center console and connected to the computer box underneath the seat. There were also some cables running into the rear right wall panel from the seat. I guess the rear well trim panel u mentioned is the wall behind the doors which I saw a cross screws covered by a plastic cap. For removing this, do I have to remove the movable hinge and surrounds?
I feel it's a pretty scary car if anyone wants to add on stuffs on this car.

I also wish someone can upload some pictures so I can have better idea about the cable route... but I guess the chance is slim though.

Thanks a lot, Hal

Anthony
 

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Registered
07 SL350, 14 BMW320, 05 SLK and 4.6 MGBV8
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745 Posts
Re Boxes - I mean the structure that the rear seat sits on - it is when you look at it a few bits of plywood screwed together. No need to take the centre console out. You may not have rear seats, and just two hinged lids. This will be a lot easier than the seats.
I do not have any photos. You will just have to get stuck in and work it all out! Do not worry, there is nothing that can go wrong!

The plastic trunking is the one alongside the step panel yes. You will need this off to route your cables to the front of the car.

Yes to the trim - it is held on by a series of capped plastic studs - prise up the cap and pull out the stud. The hinged panel you talk about is what I call the box structure that the rear seats sit on (if you have them fitted). No need to remove the main seats.

I no longer have a 129 so cannot send a pic with marks on it.
 

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Greek God of the R129
SL500-500SEL-190E
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8,371 Posts
You may want to see the dvd's in the sticky's to help you see what to remove
and how.
Look for numbers 129A1-A2-A3-B1.
They will help you a lot.
Regards.
aam.
 

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Registered
1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #7
Thanks a lot, Hal. Now I have better idea on how to do this 'big' project :).
When I removed the rear seat that night, I didn't see any 'box' underneath the seat, all I can see is the soft top computer and the chasis. But if I can run the cable under the side trim panels, I think I can run the cable to the back seat and get into the side panel with the hinged on top.
I'm now waiting for the amp to ship over and hope I can start the project next weekend.

Hi aam, thanks for your info. I 'm sure I will go for it.
 

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Registered
1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #8
Hey Ali, I've picked up the gears for you. They all look great!
 

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Registered
1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #9
Hi Hal, Ali and aam,

according to your information and pics. provided, I've successfully pulling the cable from the trunk back to the cabinet and finally to the front thru the space underneath the door sill. I used a cloth hanger to pull the cable from the back to the front. I took some pics. before I reassembled the seats and covers.
Thanks for your information and help. Now I'm waiting for the speakers and hope I can complete everything by spending a few more hours :p

However I'm sad as the electroinc throttle actuator was dead due to the rotten wire harness. The new one costs more than what I've paid for the new speakers and amp...:crybaby2:

Anway thank you again and I really enjoying surfing around benz.org:thumbsup:
 

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1993 500SL
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272 Posts
I just finished up the same...
It was a real pain in the azz. I ran the wires through the console then up the drivers side wire tunnel and into the trunk. Had to remove every thing in its path and use a fish tape to get the wires through...fun fun...Not to mention removing all that trunk stuff...

Here is a pic before its all cleaned up.

 

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Greek God of the R129
SL500-500SEL-190E
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8,371 Posts
Did the same thing but I left some cotton strings in there so I can pull
more wires if I ever need.
Be careful on the drilling the gas tank is right there.
I cemented a ply wood on the metal, screws on the wood.
I installed the amp more to the left so when you need to remove the tire or look at the pump will be more room. ;)
Regards.
aam.
 

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Registered
1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #12
Did the same thing but I left some cotton strings in there so I can pull
more wires if I ever need.
Be careful on the drilling the gas tank is right there.
I cemented a ply wood on the metal, screws on the wood.
I installed the amp more to the left so when you need to remove the tire or look at the pump will be more room. ;)
Regards.
aam.
Oh...I should have left the string like you too...:confused:
As I have the wind deflector storing at the back so I'm considering to fix the amp on a piece of plywood and hinged to the left side. I planned to drill holes at the left side of the trunk at the 'sunken area' with the drill bits pointing at the center of the trunk. Do you know if it's ok for me to do the drilling at the area? Will it be easy to damage the gas tank?
 

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Greek God of the R129
SL500-500SEL-190E
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8,371 Posts
Why take the change of drilling or the screws going in with time?
Cement it is not going away. ;)
My father used to say measure twice cut ones.
Things do bend and the vibration?
Regards.
aam.
 

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1994 SL320 (R129), 2002 S500 (W220), 2006 S550, 2012 Ducati 848Evo Corse SE
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124 Posts
Discussion Starter #14
I’ve done a test yesterday that I used the original speaker wires that used to connect to the original 6.5” mid bass at the door as the source to the cross-over of my new component speaker, the mid-bass was functioning but there was no sound coming out from the tweeter!

Is there any original ‘cross-over’ in the car that has ‘filtered’ the high frequency from the output to the original 6.5 woofer? If yes, how can I eliminate the cross-over?

I’m sure the new cross-over was functioning as I’ve done a test with my home amplifier before.

I've not installed the amplifier yet as I wanted to test before I proceed next step but seems like I don't have any luck on this project. Can anyone give me some hints?

Many many thanks.
 

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Registered
97 SL500
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1,259 Posts
you did excellent work. good luck w/stereo.

I’ve done a test yesterday that I used the original speaker wires that used to connect to the original 6.5” mid bass at the door as the source to the cross-over of my new component speaker, the mid-bass was functioning but there was no sound coming out from the tweeter!

Is there any original ‘cross-over’ in the car that has ‘filtered’ the high frequency from the output to the original 6.5 woofer? If yes, how can I eliminate the cross-over?

I’m sure the new cross-over was functioning as I’ve done a test with my home amplifier before.

I've not installed the amplifier yet as I wanted to test before I proceed next step but seems like I don't have any luck on this project. Can anyone give me some hints?

Many many thanks.
you did excellent work. good luck w/stereo.
 
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