Good evening gents/ladies/whateveryouidentifyas,
I have a recently acquired German W126 500SEL. The car has 86K original miles, not a spec of corrosion and all of its factory components.
My issue is: nothing on fuse circuit 13 is working. No radio, clock, central locking. I’ve inspected the individual components, they look fine. I replaced the fuse, cleaned the terminal, and verified that 12V of potential are present with ignition on. Ground straps are clean and in the right place.
I have pulled the instrument cluster out and verified that I have constant 12V going to the clock, so that’s confusing.
Admittedly, I suck at diagnosing electrical problems and I’m hoping somebody can help me out. Where should I look? Any clues?

wiring diagram: (page 4 is power dist.)


https://www.startekinfo.com/StarTek/outside/12253/disc%202/program/ETM/126gas83-85.pdf


are your hazard lights working?


Trace the wires in the diagram to see if you really don't get power to various systems


If you don't then the only thing I can think of that's wrong is in the fuse box itself.

Thanks for those schematics. Here are my tracing results:
I have full potential into the radio, ~13.8V running.
I have full potential to cigar lighter and it works after having the terminals cleaned.
I have full potential to clock.
My heated seats work, as do my hazards. Sadly, it seems that my German Becker 612 (EIN/AUS) is inop.
Is there a common failure point in these radios? I’d be thrilled if I could open it up, resolder some joints and party. Or an internal fuse? Anything else to look for?
If anybody is in the Denver area and has a good Becker I can test, I’d give you my soul (not worth much) and while social distancing of course.

So we're down to a non working clock and a radio?

clock shares it's ground with other instruments so I don't think that's the issue since i'm assuming that other gauges are working.

Clock is sometimes connected by a spade connector at the back of the cluster so check that it's plugged in.

As far as the radio goes I'm not sure if the radio wiring diagram applies to your radio to check the wiring. You may have to look for a wiring diagram for your specific radio model.

I found this online for becker 612:

Hey guys, I really appreciate your help with this. My final diagnosis is that coincidentally, my radio, clock and central locking pump are just dead. Car has 86K on it and the interior is NICE. Trunk has seen no water, so it is what it is I suppose. Has anybody sent there Becker to Becker for a repair/Bluetooth mod? $300 is steep but it’s a nice unit so I’ll bite if some have had good experiences.

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-1984 MB 300D Turbodiesel, 350K>
-1983 MB 500SEL Euro Import, 86K Original Miles
-2014 Audi S4 DSG, Integrated Engineering Tuned

Not that anybody cares but maybe this might help somebody out there.
No wiring schematic I have found shows the internal fuse in the back of the Becker. Mine was blown. Replaced. Radio works like a charm.
Pulled door panel as I was not getting signal to vacuum pump, connector was dangling, plugged it back in and door locks work like a charm.

SO CHECK THIS OUT: We have here, a W126 with working cruise, AC, HVAC, central locking, ortho seats, sunroof and windows. The only thing that doesn’t work is the clock. This might be the weirdest old Benz I’ve come across! Is it bad when you’re concerned at the excess of working features? This car was $1500 with 86K miles!

__________________
-1984 MB 300D Turbodiesel, 350K>
-1983 MB 500SEL Euro Import, 86K Original Miles
-2014 Audi S4 DSG, Integrated Engineering Tuned

You can fix the clock by replacing the electrolytic capacitors on the printed circuit board under the tach.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)