Radio wiring

[balimatharu]

I read some of the older forums but I am not sure about the wiring the radio.
In the radio area there is a black wire which is permanently live. Not sure if this was used to power the radio.
There are sources to get switched live.
I couldn’t find any source to get power at no.1 on the ignition switch.
None of the terminals on the fuse box gives power in position 1.
There are no extra wires around CSD.
Any suggestions where to get this power from, without cutting open the loom.
Or is it ok to use permanent live. I could put inline fuse as required.
Is there any device that is powered at no.1 position.
Any suggestions would be appreciated.
Bali

[Pawel66]

As I was studying this topic and committed a lengthy post about it, let me perhaps suggest:

1. The factory way of connecting the radio is to look for black/red wire in the harness in the area of CSV/Regulator/coolant tank support. You would need to feel the harness a bit, untie insulation or cut it a bit - chances are the wire with voltage when key is in accessory position (black/red) as well as permanently powered wire for automatic antenna (red) are there. You will not see them there unless you open the harness a bit and extract them.

2. If not, you can have it any way you want:
a) radio can be operated with key in accessory position (as factory) - there is a pin R in the ignition switch, you need to find it. You will not find this position of key in the fuse box (I think). You need to have this wire go through auxiliary fuse box, placed next to the regulator. It is a single black/red wire in the ignition switch.

b) radio can be operated any time - you can take the power form fuse 1 (permanent power). I would take it from the supply side and have it go through auxiliary fuse box (e.g. the one next to regulator or the one next to brake booster support, if not used, or any other, e.g. in-line fuse solution). There are pros and cons of this solution - you can listen to the radio anytime you want, but you may leave it on accidentally...

c) radio can be operated when ignition is on - then you start from fuse 2 for example and run the wire through an auxiliary fuse box.

Automatic antenna should be powered at all times.

I am not sure about the black live wire...

The above is based mainly on 280SL experience.

[lpeterssen]

Dear Balimatharu

Some more ideas apart from the ones explained by my friend Pawel.

1. Right way and OEM way is: install an auxiliary fuse box on the engine Bay Area next to the CSV (cold start valve) take the feed side of the auxiliary fuse box connected to a RED/GREEN cable that is where Pawel said slightly folded on the harness next to the CSV connections(not red/black, that is mistaken). Run a Black cable trough the firewall to the radio. There are some rubber caps on the passenger side next to wiper motor.  This cable Red/green comes from the ignition tumbler switch, port labeled “R”

2. This black cable that you just inserted trough the firewall to the area where the radio will be installed is a switched hot source will be active when ignition switch on the “R” position, which I believe is something between “0” position and “1” position. All I know is that this position will not energize the ignition coil which is all the engineers had in mind to avoid damaging the ignition system while listening to the radio with engine off.

If you plan to listen to the radio only when the car is running, you can avoid all this hassle and take the energy from fuse no.3, which in most cars is not used and free.

Best regards
L.peterssen

[balimatharu]

Thanks Pawel
Mine is 250sl RHD. I had a look at the wiring loom. Most of it is hidden under the brake booster.
I think I will go for switched live from fuse no.2.
My car has gone through almost nut and bolt restoration. Full body panel restoration, wings inner wings. Complete full back end.
Originally had a manual aerial at the left back corner. I was thinking of not making a hole for the aerial instead have a some sort of internal aerial for now.
It is going for full reupholstering booked for April. I will send an aerial, permanent live and a switched live cables from front to the boot for later use. Will that be enough?
I bought a new old becker europa kurier on eBay from Lithuania.
Back of the radio black cable will take power.
Also there is a spade connector with 2 terminals. One of them is marked +ve. I assume this connects the radio to the electric aerial. Keeping this in mind how many cables should be sent to the boot area.
Please advice.
One out of context question. My car is silver and black interior. I don’t particularly want to put black leather. I think your car is also silver but with red leather. What colours leather would be acceptable and would look nice.
Couple of photos of my car

Bali

[Pawel66]

Your car would look beautiful!

Mine is 180, but with dark. Blue interior, upholstery code 245.

As for the antenna - you need permanent power there and the signal wire from the radio. Ground as well, of course.

Wiring the radio - i am afraid to advise anything, i do it by a hit and run method.

[balimatharu]

Pawel. Thank you

[johnk]

wow! Impressive rebuild. Still amazes me the talent to reconstruct the body like that.

[balimatharu]

John don’t get impressed. It wasn’t me in my garage. I had to get it done by a body shop who specialise in classic cars.

[lpeterssen]

Dear Bali

To the trunk you should send two cables, the third will come from a ground taken locally near the power antenna connection. 

1. Constant 12v which is called a T30 connection (fused). Take it from fuse no.1 at main fuse box and use an inline fuse just after in a place that can be serviced.
2. A trigger signal from the back of your radio. Locate the only single port that is behind it with a spade connector. Take photos and send to me per regular email.
3. The ground already mentioned before taken on the trunk itself on the already existent ground post.

The cable 1) should be RED size awg16
The trigger cable should be BLUE size awg 18. Not smaller since can be broken on the cable routing, nevertheless the power consumption will be minimal.
ground in BROWN, awg 16 as well.

Best regards
L.peterssen

[balimatharu]

Peterssen.
Back of the radio has two spade terminals. One is marked as +ve. See the photo attached. I think it is for the automatic aerial. But there are 2 terminals.   
The second picture shows the wiring as I could understand from the post. Will this work.
Only issue is the 2 spade terminals
 Thanks.
Bali

[balimatharu]

Pawel. Thanks for your feed back.

[lpeterssen]

Dear Bali

Yes your drawing with the electric schematic is correct. You got our instructions right.

Regarding the spade connectors on the back of your radio. Not sure. One I see is labeled “+” and the other I can tell.

Which model is your radio to make a search on internet and confirm what is correct?

I guess you have a din connection between your radio and an external amplifier..... because I do not see speaker output connections there...


Best regards
L.peterssen

[FGN59]

Not sure this will help, but you never know...

I have a Becker Europa II Stereo, with a closely related wiring scheme (see picture):

- the black wire coming out of a round black plastic hole with a red dot is for the power to the unit (far right, middle height)
- the black wire coming out of a rectangular black plastic hole is the antenna trigger (next to the left of power wire, bottom of unit)
- the two similar black and white round connectors arranged in a vertical line are for the speakers

Hope this helps

[balimatharu]

Francois. Thanks for the replying.
You are right. Mine is mono so only one speaker outlet. Yours is stereo.
The spade outlet has to be the aerial trigger.
Thanks all for the help.
Bali

[teahead]

FYI, my radio turns on at at position 2 (run), however, I wired this to the dome light (the terminal with two wires):

Revolution Electronics Radio Power Controller for Classic Ford Vehicles https://a.co/d/9LoWw26





and it works awesome!  Stays on at position 1, or position 0 (where you can pull out the key) until you open the door or 15 minutes goes by

[rwmastel]

I think the aftermarket radio in my 230SL is connected to power all the time.  I don't know if that is factory correct.  Maybe it got wired that way by whoever put in that radio.  Anyone know the correct/original configuration, and did it change during the production run?

[teahead]

There's a special bracket that ties into the harness (as Pawel66 mentioned earlier in 1.) w/its own fuse that is near the coolant tank.

https://www.authenticclassics.com/Fuse-Box-With-Bracket-Mercedes-230SL-280SL-p/auth-007124.htm

That supplies power ONLY when the switch is in position 2 (RUN).

So most likely what you have is NOT CORRECT!  Plus it can drain the battery if you forget to turn it off.

Best to re-wire it to OEM configuration AND...use that cool adapter/thing I referenced so you can listen to tunes in your rig w/the engine off and not have the battery drained down quickly.

[rwmastel]

When I get my hands on a Becker Grand Prix (what was originally there per data card), then I'll worry about how to re-wire it.  That's an interesting argument you make.  "Go back to original, then add this non-original thing."

[DavidAPease]

I have a relatively original '66 230SL as well.  My car has option 535 (auto antenna, noise suppression, no radio set).  The radio is connected through the auxiliary fuse box (as referenced above).  Like Rodd, my radio always has power, and I have believed that this was how the earlier cars (if not all 113s) were my wired. (In other words, not through the ignition switch.) 

Can anyone say with authority that this is not the case?  How about other 230SL owners?

     Thanks,

        -David

[teahead]

When I get my hands on a Becker Grand Prix (what was originally there per data card), then I'll worry about how to re-wire it.  That's an interesting argument you make.  "Go back to original, then add this non-original thing."

Well...you could always leave it the way it is and risk running the battery to dead.

[Lorsar]

https://www.sl113.org/wiki/Electrical/Radio#toc-1.9.11

[DavidAPease]

Lorsar,

Thanks, I went looking for that in the Tech Manual, but didn't go down deep enough.     So it seems that it is "standard" for the early cars to have constant power to the radio (especially since there's no accessory position on our ignition switch).

teahead,

You're right, of course, that there's the chance of leaving your radio on and running down the battery.  However, I was trying to differentiate between "better" and original, for those who care about such things.

        -David

[teahead]

These radios were installed by the dealer.

WHo knows, maybe some did it different than others.  Or maybe the factory bracket/fuse holder was a later addition MB decided to offer dealers for wiring up radios since early cars always had folks running down their batteries???

What's "correct" doesn't always mean better functionally.  Especially since it's for something that no way you can tell otherwise by looking at it visually.

[rwmastel]

I'm "only" 56 years old, so only have 40 years of licensed driving experience, but I've never run a battery down because of a radio.  Maybe it will happen when I eventually have memory problems.