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  #1  
Old 07-12-2011, 03:01 PM
Appollon's Avatar
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aftermarket radio wiring help '82 240d

Hello, all!

I just purchased a 1982 240d, and I'm trying to replace the Becker unit with an aftermarket head unit.

I am not using the original speakers or wires. I re-ran audio cables throughout the car.

My question is regarding the original power and the ignition switch. I don't knwo which one is supposed to connect to the ACC thing on the new wiring clip so that the radio only has power when the car is on and which one is supposed to go to the hot power from the battery.

Here's a pic of what I have





I see a brown wire and a red wire for power. One of them has a circular ring on the end that was screwed into a nut on the back of the becker unit itself.

I guess my concern is that I want to make sure that I have it grounded correctly, and that the stereo is only going to bbe powered when the ignition is turned, and finally that I didn't miss something that's going to make the antenna not raise anymore.

Here's what I went with for the ground from the head unit's new wire coupling.


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  #2  
Old 07-12-2011, 03:06 PM
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I'd run a fused wire directly from the battery through the firewall. Less possibility of electrical noise, plus 99% of new radios use the wire hooked up to the ignition only to turn them on (via a relay). The main power is drawn from the "always on" connection, and it can be 10-15 amps. The interior lighting circuit can't really support that kind of current.
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  #3  
Old 07-12-2011, 03:15 PM
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I would splice into the wire which goes to the clock, thats what i have always done.
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1976 240D 190,000 miles
1979 300TD 220,000

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  #4  
Old 07-12-2011, 03:15 PM
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Here's the info I have.
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aftermarket radio wiring help '82 240d-screen-shot-2011-07-12-3.12.52-pm.jpg   aftermarket radio wiring help '82 240d-screen-shot-2011-07-12-3.13.07-pm.jpg  
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  #5  
Old 07-12-2011, 03:19 PM
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It is a piece of cakee to wire radio.

Measure the old wires with a DMM

1) 1 wire is constant 12V to remember radio setting with key is off
2) 1 wire is switched 12V when key is in posn 2 to turn radio on
3) 1 wire is switched variable 12V when parking light is on for dimming. It may not exist with old cars.
4) 1 wire is ground, probably brown as MBZ uses brown color.
5) 1 wire activare the antenna.
6) Speakers wires.

Once you identify all these wires then you should be able to hook up the new radio.
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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
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  #6  
Old 07-12-2011, 03:22 PM
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Quote:
Originally Posted by 79Mercy View Post
I would splice into the wire which goes to the clock, thats what i have always done.
You're talking about a circuit fused at 8 amps that has a clock (negligible current), an interior light (~1 amp), a trunk light (~1 amp), the power antenna (~3 amps), the rear cabin light (~1 amp) on it. The Mercedes electronic radios used the always-hot wire just for the station memory, which drew little current. Modern radios use it to power the entire radio. If you do it your way, be prepared to blow fuses.
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  #7  
Old 07-12-2011, 04:12 PM
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Quote:
Originally Posted by ah-kay View Post
It is a piece of cakee to wire radio.

Measure the old wires with a DMM

1) 1 wire is constant 12V to remember radio setting with key is off
2) 1 wire is switched 12V when key is in posn 2 to turn radio on
3) 1 wire is switched variable 12V when parking light is on for dimming. It may not exist with old cars.
4) 1 wire is ground, probably brown as MBZ uses brown color.
5) 1 wire activare the antenna.
6) Speakers wires.

Once you identify all these wires then you should be able to hook up the new radio.
X2, a simple DMM or even a $2 test light will be your best friend. I keep a test light and DMM in my audio toolbox at all times becuase once the wires are all cut and disconnected its a heck of a time figuring it all out. IIRC (this is totally off the top of my head):
- Brown is ground in MB (always)
- Red is constant 12V
- black with yellow is Acc power (these two might be switched)
In my MBs I've cut into the cigarette lighter circuit since its got all the connections right there. The 4-prong plug from the original Becker radio should have all the connections as well.
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  #8  
Old 07-12-2011, 04:30 PM
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radio blues

Ah-kay is correct, but what he didn't mention with new head-units which are usually 200W peak performance, you don't want to use the original fader switch. Just bypass it!!!! The original Beckers were low-watt systems, and if you use the fader near the shifter, you run the risk of burning down your car!!!! LOL. I tried to tell that to the radio shop that installed my Explode Sony unit, but the next day I noticed how hot the fader switch was . . . almost melting point, so I had to go back to the same radio shop and we fought about who was gonna pay for the rewiring job. Fortunately, my receipt from the day before specificially told them to "double-wire" and bypass the fader, so I refused to pay for them to fix it. It was a fight that brought the cops, but when I showed the cops the receipt, they told them that they were on their own. I did wind up "comping" the installer who fixed the problem, but I made sure the owners were the wiser for their effort. Also, the original speakers were a 1-wire system, which you also want to change. Your new headunit should have two wire setup. I later added an amplifier and put two box speakers on floor of back seat, as I couldn't hear anything out of the deck speakers . . . Really poor acoustic design. Doing my box speakers worked extremely well, and that's when I ran a direct line from the battery . . .to feed the amplifier (small 2-channel amp given to me by a friend). All other wires were just as described above, and after we cleaned up the mess left by other installations, it installed very easily. Now I just have to change my antennae again!!!
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  #9  
Old 07-12-2011, 04:48 PM
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It is unlikely that an in-dash radio would have a 200W peak or RMS output without a Power Amp. If there is one then you probably need to wire up the Power amp separately with a hefty fused 12V, directly from the battery.

I do not understand why the installer reused the fader by the shifter. The fader circuit in old MBZ is NOT a true Front/Rear 4 speakers setup. One must run separate wires to the rear speaker, or cut the wire at the fader to by-pass it completely to have true F/R speakers. If your new radio has F/R channels then the fader need to be by-passed. Speaker wires should be easy to sort out but make sure the phase is correct. Some radio or power amp also has subwoofer set up, so there could be a lot of speaker wires. Control wires are all the same.

Audio equipment - radio, power amp, subwoofer, speakers, tweeters and monster cable could easily worth more than the old MBZ.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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  #10  
Old 07-12-2011, 04:52 PM
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Quote:
Originally Posted by ah-kay View Post
It is unlikely that an in-dash radio would have a 200W peak or RMS output without a Power Amp.
Who said anything about 200W out? 60W input (which says little about output power, since electronics are not 100% efficient) is 5 amps, which could blow the 8A fuse if you have the antenna and interior lights running at the same time.
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  #11  
Old 07-12-2011, 05:03 PM
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Wow! The Speed!

That was my first post over here, and I didn't have the settings right yet to have it email me when I got responses. I've been searching the net ever since I made that post, which led me back here, only to see that there has been a TON of responses! Thanks guys.

Also, I just realized that I likely posted this in the wrong place, and should have put it in the audio section. Sorry about that.

So, I'm still very confused here. The more I learn this afternoon, the worse it seems.

So, let me re-cap, and let me put in what I've taken from the conversation, and then maybe see if I'm reading it all wrong, and am, in fact a moron.

Ok, so, the ground to the ash tray that I have set up now is no good. I'm going to need to also take that ashtray out in order to see the other wires that I'm missing now, specifically, the blue wire for the antenna power.

As it stands now, I have a huge marine cable run from the battery to the trunk and connected to an amplifier and two 10 inch Jenson subs. I have a ground coming from that amp and going to one of the bolts that holds up the carpeted wall between the gas tank and the trunk. I neglected to run the wire from the amp to the new wiring harness that tells the amp not to power on unless the car is on (the remote, I believe it's called).

However, my concern on that blue wire is that I think that the antenna is supposed to be wired to that so that it extends on powerup. Am I supposed to splice the remote for the amp and the antenna together with the blue remote from the head unit??

Right now I have the brown wired as constant power, but I believe now that it is a ground. If I am using the ground from the current new wiring harness, can I disregard the original factory brown ground?

It appears I'm also going to need constant power as well. I think the best way is to run a wire directly to the battery. This is no big deal, as I already have pretty easy access through the firewall, as I haven't sealed it back up yet from running power to the amp. I guess my only concern there is how do I get a clean addition to the battery with a small wire like that? I don't really know what I should splice it into.

I also realize that this all may be easier for me to grasp once I'm back at home looking right at the whole thing, as opposed to working off of photos and memory.
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  #12  
Old 07-12-2011, 07:46 PM
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New speakers and speaker wires, so the fader is no longer an issue.

You're trying to connect the following to the new HU to get functions:

1) Switched power so the radio turns off with the ignition
2) Steady power so the radio doesn't lose presets
3) Ground
4) Accessory signal for antenna and amps
5) Maybe - a variable voltage to adjust intensity on the lights w/ instrument lights

This thread has some info on the 240D. It's important to remember the 240D was more basic and may not have the same OE wiring harness as a 300D/CD/TD. Specifically the 240D may not have the requisite steady +12v for those "deluxe" solid state radios. New Stereo Install 1979 240D


You can buy adapters or eyes that will let you tap directly off the battery. For your trunk mounted amp off the marine cable, get one of those and install an inline fuse near the battery in the engine bay.

For the amp "remote", yes, you can splice the antenna "trigger" wire and the amp "remote" wire to the blue wire from the HU. The antenna does not draw power for the motor from this wire so you won't be drawing too much current. For the 240D with the power antenna the wire should be Blue/Red or maybe black or maybe blue.

More info here: Once again, trouble replacing stereo

Matching these up with the above list:

1) thickish red wire from the harness for ignition switched +12v
2) probably better off your battery tap - but maybe off the dome light
3) the brown wire for ground -- but if you've already got a good ground elsewhere on the new harness you don't NEED to use this wire.
4) blue/red between radio and antenna switch for +12 when radio on
5) maybe the grey/violet wire going to the lights, if you're adventurous

Get a multimeter, use the continuity and voltage functions, check wires in different settings (e.g. ignition on/off, lights on/off). Check fuses before you start and read up on a few other installs. I think fuses 1, 2, 4 and maybe one other one can affect the W123 install on the 300D, maybe on the 240D, too.

Last edited by Yak; 07-12-2011 at 09:54 PM.
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  #13  
Old 07-13-2011, 10:23 AM
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Or . . . . you can do it the easy way and go to a auto radio shop and pay $100 to have them install everything for you. LOL. BTW, what radio/model are you installing, with what accessories (i.e., CD player, CD Changer, tape deck, DVD Player?)
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  #14  
Old 07-13-2011, 11:21 AM
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Wow, Yak. Very helpful response. Thank you.

Ok, I think I got it all right.

I took a speaker wire and split the two leads. I ran the single wire from the console, through the firewall, and put an o ring on it and attached it to the battery terminal. The heavy duty marine cable already has a built in fuse box right next to the battery as well. I connected that to the battery terminal as well.

I disregarded the original brown, mercedes ground. I removed the ash tray and the center console and screwed the ground from the new wiring harness to the bolt that attaches the shift knob.

I spliced the antenna and the remote line for the amp and put them together as well. That one was black off the back of the Becker, but when you peeled away the first black rubber, you can see that it is actually a blue wire with a red stripe. I ran the red as the ignition 12v and the speaker wire to the battery as the constant. I plugged it all in this morning and it worked like a charm. Antenna went up automatically when I turned on the head unit, and the amp powered up at the same time. I didn't blow any fuses and all the lights and wipers and interior lights and warning buzzer all still work too.

However, the subs aren't making any sound. I'm hoping it's a setting on the HU that I have to "turn them on" or something like that, and not that they are either bad or wired wrong.

My set up is 2 Planet Audio 100w 6in speakers in the rear shelf, 2 4in Kenwood 3way 120 watt speakers in the dash, I have a US Amps Xterminator 1600.2 Amp running 2 10in 200w Jenson subs, and I have a Pioneer DEH-1300 head unit with a remote and Ipod/accessory on the front input.

I bought a monster wiring kit that came with the huge marine power cord with the fuse box built in, a huge marine grade wire for the ground, nice thick wiring for the subs to the amp, the long remote cable for the amp, RCA cables, and zip ties. I also bought 50 feet of the brand below monster (can't remember the name) of speaker wire and used that to run the four speakers and the constant power.
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Old 07-13-2011, 02:32 PM
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Quote:
Originally Posted by Appollon View Post
Wow, Yak. Very helpful response. Thank you.

Ok, I think I got it all right.

I took a speaker wire and split the two leads. I ran the single wire from the console, through the firewall, and put an o ring on it and attached it to the battery terminal. The heavy duty marine cable already has a built in fuse box right next to the battery as well. I connected that to the battery terminal as well.

I disregarded the original brown, mercedes ground. I removed the ash tray and the center console and screwed the ground from the new wiring harness to the bolt that attaches the shift knob.

I spliced the antenna and the remote line for the amp and put them together as well. That one was black off the back of the Becker, but when you peeled away the first black rubber, you can see that it is actually a blue wire with a red stripe. I ran the red as the ignition 12v and the speaker wire to the battery as the constant. I plugged it all in this morning and it worked like a charm. Antenna went up automatically when I turned on the head unit, and the amp powered up at the same time. I didn't blow any fuses and all the lights and wipers and interior lights and warning buzzer all still work too.

However, the subs aren't making any sound. I'm hoping it's a setting on the HU that I have to "turn them on" or something like that, and not that they are either bad or wired wrong.

My set up is 2 Planet Audio 100w 6in speakers in the rear shelf, 2 4in Kenwood 3way 120 watt speakers in the dash, I have a US Amps Xterminator 1600.2 Amp running 2 10in 200w Jenson subs, and I have a Pioneer DEH-1300 head unit with a remote and Ipod/accessory on the front input.

I bought a monster wiring kit that came with the huge marine power cord with the fuse box built in, a huge marine grade wire for the ground, nice thick wiring for the subs to the amp, the long remote cable for the amp, RCA cables, and zip ties. I also bought 50 feet of the brand below monster (can't remember the name) of speaker wire and used that to run the four speakers and the constant power.

Is your amp hooked up to 12V+ and accessory power as well? If the subs aren't working at all I'd start there. My pioneer HU does allow for turning the sub off or reversing the polarity but its a DEH-5000UB which has a lot of audio flexibility

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