Just discovered the 4 black speaker wires are actually:

2 black wires and 1 half black/half green, and 1 half black/half red.

ok. looks like a retard wired it. twisting wires and tape is mickey mouse. first, pull the lower control panel and disconnect that stupid fader switch. you can't hook up the radio properly w/ that junk hooked up. the blue wire should be for the antenna, there should also be a constant hot wire for preset memory. you will need to test each pair of speaker wires to see which is which, unless you have already checked them at the speakers. you would think red=right but w/krauts who knows. if speakers have been replaced or not, make sure you wire them consistently. black should be -, but krauts might do it backwards, and the po might have them all mixed up. they sell crimp terminals w/ shrink tubing on em that work real good, but you need a heat gun.

i would start the car w/ the radio completely disconnected to verify whether it has anything to do w/ the blown fuse.

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1984 300TD "MAX" 303K+ still going...
fast '70 Chevelle 200k+
home built Shovelhead chopper

Yep its real sloppy! So sloppy Im guessing it has to be the cause of the blown fuses. I believe that blue antenna wire is hooked up to the yellow constant power wire on the harness...so things are pretty messed up. I have crimp caps, so hopefully I can redo it sort of neatly.

Any idea what color the constant power wire is on an 83 240d?

I believe the speakers are original. I only tested them a little, but they seemed to be set up correctly (l+r etc)

Finally..what exactly does the fader look like? I can't find a photo, just references to it. Is it under the gear shift console? Or is it behind ashtray area? Sorry for so many questions, Ive never done this before. Can you tell?

Thanks a ton!

The key has four positions: Off, Accessory, Run and Start. Just want to be clear here. I'm assuming the first part of your response means that the radio would work when the key is turned to the Accessory position. Does it blow the fuse if you then turn the key to the Run position (without starting the engine)? Or does it blow the fuse when the key is turned to the start position?

What I'm getting at here is that Fuse 4 is supposed to be hot when the key is turned to any of those positions. If the radio works when in Accessory, the radio shouldn't blow a fuse when the key is turned to start. There's nothing essentially different about how the radio operates in any of those positions. I'm going to guess the radio is not going to be the cause of your problem. Getting it wired properly is important, but since it works when in Accessory, it shouldn't blow a fuse in Run. My guess is that's a symptom, not a cause. In fact, I would guess that none of the other items normally in the Fuse 4 circuit are going to be the problem.

The riddle of this then becomes... What circuits/relays are engaged when running that aren't engaged when in Accessory, and how is this connected to Fuse 4?

Hypothetically, if Fuse 4 were somehow connected to the starter motor then when the starter motor was engaged it might draw enough current to blow the fuse. But this wouldn't be evident until the key was turned to the start position. Radio would work until the starter was engaged. I'm not saying this is the case; it's highly unlikely. But it fits the scenario. That's why it's important to know at which key position the fuse blows.

The only question I would ask at this point, other than the ones in my first paragraph, is "What other electrical items don't work and do you know why they don't work?"

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

Really great points. Tomorrow I will try to pinpoint exactly when the fuse blows. I didn't realize the significance of the timing until you put it like that. Thanks.

69shovlhed suggestion to see if I blow a fuse with no radio at all is also a real good call. Really appreciate all the ideas here!

Im starting to think theres a good chance that black loose wire in the 3rd photo I posted might be the switched power wire. It would certainly make sense.

Wow that's some crap wiring.

I think the red wire and brown wire coming out of the black sleeve should be the ignition-switched +12 and ground that connect up to the ashtray plug. You may be able to verify this by tracing it back. If that wire is bad - either disconnected at the cigarette lighter or chafed or cut, then that could explain why it works off the battery (yellow + grn/wht) and shorts on the switched (bad/loose red).

I would have expected two other wires in that sleeve, though. One for the headlight rheostat and one more for a constant power for the clock. But...on the 240 maybe only a basic radio was an option so they didn't need constant power and the lights in the radio didn't dim so maybe that makes sense.

That other wire going to yellow looks like it's supposed to be the +12 to the battery. Is that green w/ a white stripe?

The loose black wire 'might' be the trigger wire for the antenna. It's a black wire in some models. I think I built a male spade connector w/ plastic housing for mine so that connector would work. You can try to follow that up the console into the antenna switch. Or pop the antenna switch and see if the other end of the wire is up there.

Are your speakers wired as 8 wires going into 4? It looks like the PO simply put the front and rear + together and the f/r - together.

The fader (if you have one) is the little wheel behind the shifter. I think it adds 40 ohms to the channel that you "turn down". You can tell if it's already bypassed by unplugging it. If not, and the wiring isn't already cut up, I recommend unplugging the rear speakers. Check the pic in the PM I sent and there's a photo of the fader harness. The system uses a common ground for front and rear speakers since the factory Becker only had two outputs.

Yes, you should do something with the loose cigarette lighter harness. For short term troubleshooting I'd make sure the radio is plugged in securely to the pig tail, then tape it.

Red = left. You can tell by the small L on the white cap on the left side connectors that connected to red and black wires.

Do you have two other wires unaccounted for? An orange wire and a blue wire coming out of HU?

The orange wire would normally connected up to the dimmer on the instrument panel and the blue wire is the output from the radio to tell the antenna to go up, or turn on an amp. These both should be capped/taped if they're not connected.

According to the schematic...

1.5mm^2 Red wire => Switched Power (Fuse 4)
.75mm^2 Red wire => Hot at all times (Fuse 2)
.75 Blu w/ Red Stripe => Antenna / Amp signal (antenna relay or power sense for amp)
.75 Blk w/ Red Stripe => Illumination
1.0 Brn => Ground
.75 Blk w/ Red Stripe => LH Speaker
.75 Blk => LH Speaker Common
.75 Blk w/ Grn Stripe => RH Speaker
.75 Blk => RH Speaker Common

You'll need a light bulb or multimeter to test the diff between the similar color wires. You can use a 1.5 V battery to test the speakers, just a quick touch and you should hear the speakers react.

I agree regarding removing the fader, run front/rear wires to the fader and connect to the speakers where the fader sits if you want to retain the ability to revert the stereo setup.

__________________
mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

see what i mean? the goose steppers do everything backwards. anyway, they do leave enough wire to run all 4 speakers up to the back of the radio so you can hook it up correctly. at least they did in my td.

__________________
1984 300TD "MAX" 303K+ still going...
fast '70 Chevelle 200k+
home built Shovelhead chopper

Unfortunately today got busy and I didn't get a chance to make any progress. Tomorrow I will spend some time on it. I found this in another thread:




Here's the basics of the factory wires:

Brown = Ground -
Black = Switched Ignition +
Red = Always on + (memory)
Grey = Dash Lights (dimmer)
Blue = power antenna






This would make a lot of sense. That loose black wire in photo 3 could be the black switched ignition wire. Because it was loose maybe it was causing a short when I started up?

The wire going to yellow looks to me to be a faded clear blue wire. Im guessing that means its the antenna wire.

Thanks for the help finding the fader. Hopefully I can get this straightened out!

I didn't see any other loose wires, but at this point it wouldn't surprise me if they are buried back there somewhere. I'll really give a good look tomorrow. Really appreciate the help!

Huge thanks! It looks like different years used different colors. The more info I can find, the better the chance I can unravel this. Great idea about the battery!!

You mean the antenna switch in the dash..correct?