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'72 350 SL
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375 Posts
Discussion Starter #1
Yesterday I installed a new head unit in the SL (after returning one that didn't work properly).

The wiring in the dash is a bit of a mess, but originally using a multimeter I pretty much nailed down the important wires. A blue wire supplied the constant 12V, and I had an earth and a switched power supply.

In the beginning all was well but at some stage during the install the blue wire ceased to give any power at all.

What I'm wondering is what might have caused this? Also if I can't get power from the wire, is there any other source of 12V under the dash that I can use to keep the stereo powered. (Currently I have the switched power only that causes the memory to blank every time the car is switched off).

And while I'm here ;), my antenna connection has two wires (black and red) 'stuck' to it - what are these? I don't think I used them before when I had the power antenna working - and as it currently isn't I guess I need to find out...

Any help would be good!
 

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'80 450SLC Afro RHD Ikonengold
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2,956 Posts
Here's diagram, it may help if you are electricaly literate (I presume so since you are installing headlights your self).
450 comes along just if you may need to compare or something
 

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'72 350 SL
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375 Posts
Discussion Starter #3
Thanks Djenka,
I'll print that off and have a look. Suspect I won't be able to make much sense of it though... :surrender:
 

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1980 450SL & 1988 560SL
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1,667 Posts
I was looking thru the wiring prints and it looks like the hot for the radio is brown. The blue wire at the radio goes to the antenna switch.
 

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'72 350 SL
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375 Posts
Discussion Starter #5
Nascar Fan said:
I was looking thru the wiring prints and it looks like the hot for the radio is brown. The blue wire at the radio goes to the antenna switch.
That may well have been the case originally, but the wires poking out the big gap in my dash are far from original!

They've been altered by a less than fastidious owner who used their favourite colours as they went along...
 

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2004 CLK 240 Coupe
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11,379 Posts
ConorD said:
Yesterday I installed a new head unit in the SL (after returning one that didn't work properly).

The wiring in the dash is a bit of a mess, but originally using a multimeter I pretty much nailed down the important wires. A blue wire supplied the constant 12V, and I had an earth and a switched power supply.

In the beginning all was well but at some stage during the install the blue wire ceased to give any power at all.

What I'm wondering is what might have caused this?

<snip>

Any help would be good!
Blown a fuse, maybe?
 

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'72 350 SL
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375 Posts
Discussion Starter #7
keyhole said:
Blown a fuse, maybe?
Y'know what? That could be the simple solution! When you hear hooves - don't think of zebras.
Now where did I leave my torch? :)
 

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2010 Mercury Milan Hybrid, 1993 BMW 325i convertible
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ConorD said:
Now where did I leave my torch? :)
Is it with your pitchfork and angry villager clothes?
 

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'72 350 SL
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375 Posts
Discussion Starter #11
keyhole said:
Blown a fuse, maybe?
A great evening's work! Turned out an 8 amp fuse had blown after all. Replaced this and my permanent 12V supply came back. Hooked up the new unit no probs.

In case anyone cares the black and red wires attached to the antenna connect to the antenna wire from the head unit, and the permanent 12V supply respectively. Took me ages to figure this out as the earth had come loose in the antenna motor and I had no idea.

Happy days now though.
 
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