looking for help with electrical problems on a 280

[n/a]

I'm helping a friend put a 280SL back together and we've run into a few electrical snags.

the first is the side markers don't work and I can't for the life of me figure out where they are fed power from.  The wiring digrams I have out of the Mercedes manuals don't list any color codes and it doesn't match up at all to what's in the car anyway.  For instance the service manual and the owners manual show that the right/left parking indicators work.  Meaning the two positions on the headlight switch to the left of center for actually leaving the car parked.  The two terminals for that purpose on the headlight swtich don't have any wires attached nor does it look like there ever were wires attached.
The color of the wire that feeds the side markers appears to be white w/ green tracer.  I can find that on all four corners of the car but not under the dash and certainly not at the head light switch.  Any ideas?

The middle red light in the instrument cluster is apparently for the brake fluid level (according to the owners manual) but it goes on and off with the opening and closer of a passenger door?  What the Hay is that all about?

A large part of the wiring harness was retaped in the engine bay but we striped a bunch of that back and I can't find any evidence that it's been messed with at all, just retaped.  That still has me worried though.

Otherwise it's coming together reasonably well.  Green on Green and a green top 1970 280SL automatic.  Sounds awful but it looks really nice.

thanks for any help.

[A Dalton]

The red lamp is both a Door Ajar and Fluid Warning Light circuit test verification.

 The only problem is if the fluid is low and door is left open , the fuel pump will run [ a diode modification can be done to rectify this unforseen problem]
 Check to swee if the side markers wire feeds come off each corner lighting unit.

[mdsalemi]

Speedy,

Regarding your side markers (as opposed to reflectors), they get power from the closest tail lamp assembly or headlamp assembly respectively.  There is a "pigtail" coming from each marker, and these plug into the assemblies.

Now comes the rub--if you don't have the proper receptacles on your tail lamp and headlamp assemblies, you actually have the wrong ones on your car.  This is not an uncommon problem on restorations.  There were three different US Spec headlamp assemblies, and at least two tail lamp assemblies--manybe more.  They look the same from the outside, but the wiring and assembly are different.  It is rare for a parts seller to know these differences.

You can, if you want to, purchase a receptable and splice it into the lamp assemblies to provide a place to plug in your markers.  You could obtain the proper lamp assemblies, or you could forget the receptacles, and do a cut and splice job.  Lastly you can replace the markers with reflectors.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[n/a]

Well that explains a few things.  We had the fuel pump running with the door open at one point and what really concerned me was that it suddenly stopped doing it.  Now I know why.  I'd be interested in the diode mod.  On the other hand the fuel pump never stops running either.  I would have thought for sure these cars would have had a relay to shut the pump off?  If the key is on but the car isn't running the fuel pump just runs and runs.

As for the lights, I had considered that the wrong lamps were installed but I don't think so.  All four marker lights are actually lights, not reflectors with all the necessary holes, clips and wires to connect them.  the headlights and the tail lights have the proper connection.  The problem is they are fed power from a different pin on the plug than the parking lights in the clusters.  If I back feed power into the pin at the headlight both the front and the rear side marker light up, so I know that wiring is good, and probably factory.  What I can't find is where that white/green wire originally comes from and why it doesn't have 12V on it.  I'll splice it if I have to but I'm sure it can be fixed properly.

I also don't have any dash lights.  I'm assuming the resistor is shot but apparently that resistor is no longer made.  I'll deal with that after I get the side markers working.

[A Dalton]

<<Now I know why. I'd be interested in the diode mod. On the other hand the fuel pump never stops running either. I would have thought for sure these cars would have had a relay to shut the pump off? If the key is on but the car isn't running the fuel pump just runs and runs.>>

  The pump is hard wired to ignition and it runs constant as there is a return fuel loop to tank  to eliminate possible vapor lock conditions. [ we actually use that feature when VaporLock is suspect by leaving key in Run position for 5/10 secs before crank to clear the lines ]
 The reason for the diode is to eliminate the possible feedback of the two circuits.  In order for Benz to have both door ajar and fluid warning with only one lamp left in Kombi, they rewired to existing harness mapping , but did not forsee the possible feedback of 54/30 FP circuit under low fluid condition [ which, I must say, I was always surprised to see them miss this..must'a been Beir Fest time..]
 ..any how.. the diode goes anywhere in betweeen the fluid sensor and kombi lamp, allowing for current feed in one direction only . Diode polarity pos/+  facing lamp  .. small, 1A diode is fine

[n/a]

Well that answers a few more issues and it's much appreciated.  What I really need still is a wiring diagram that is actuually correct for this car and/or has wire colors for the six pin plug on the headlight.  How about the dash back lighting?  Anyone know of a replacement for the dash resistor or do I have to bridge it?  Or put a resistor under the dash and tie it cleanly into the instrument cluster?