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· Registered
1991 300SL
2 Posts
Discussion Starter · #1 · (Edited)
I'm looking to put a new stereo in my 91 300SL (pre-Bose). When I bought it, it had a rear Sony CD changer and an Eclipse head unit. I have taken out the changer and want to replace the head unit with an Alpine.
Two spkrs in each door (lg, sm) and one in each side of the dash. Don't think the dash speakers are working/hooked up. I would like these working.
Here is the key I'm going by:

+Red..............12v ignition
+Yellow...........12v battery
+Blue.............Power antenna
+Blue/white.......Remote turn on
+White............Front left positive
-White/black......Front left negative
+Grey.............Front right positive
-Grey/black.......Front right negative
+Green............Rear left positive
-Green/black......Rear left negative
+Purple...........Rear right positive
-Purple/black.....Rear right negative

Am I missing something, or are two channels missing? - Solved, I think, by bobterry99.

I need to find the 2 dash speakers' wires so I can hook them up to the head unit. Not sure where they are.
Hoping for an end result similar to original config as stated by bobterry99.

Will update.

· Registered
2009 Chevy Z71 4x4 Crew Cab, 2006 Chevy Corvette Convertible, 2008 Harley V-Rod 1990 300SL
90 Posts
I don't have any answers for you, but thanks for the wire ID's. I have a 90 300sl and all the radio wires are dangling free from my radio.

· Outstanding Contributor
2005 SL600, (2) 2003 SL500
4,604 Posts
Questions/goals are:
1. How can I identify those 2 missing channels on the above key?
2. Get those 2 dash speakers working.
3. Would it be better to get a 4-channel HU and connect it to all 6 channels OR just get a 6-channel HU?
I think you would find a good electrical schematic very helpful. For that I recommend the R129 Tech DVD you can buy from MBUSA for about $90.

The 2 dash speakers were originally wired in parallel with the smaller speakers (midranges) mounted in the doors.

The original setup was bi-amplified. The head unit powered the tweeters in the dash and the midranges in the doors, and a separate amplifer powered the woofers in the doors.

· Greek God of the R129
8,735 Posts
I had one speaker in the left side of dashboard the right side was empty, but the wires were in there.
Traced the wires down to the head unit and connected them with the door speakers.
Got in two tweeters and It was done.


· Registered
1991 300SL
2 Posts
Discussion Starter · #7 ·
Thanks for input so far.
On a slightly different track, I noticed that when the previous owner installed the Eclipse stereo, he apparently disconnected both the rear receiver and the front amplifier. Would reconnecting these be a good or bad decision?
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