Electrical..Brake and tail lights

[Ghowe]

New member...own 71 280sl., papyrus white, blue leather..

Just had dash lites and heater levers replaced, all ok now..had driver side low beam headlight fixed that would not work but high beam worked (weird, as it was not the bulb as I checked bulb by switching bulb to passenger side where it worked)..now headlights work ok, but since the repair, now brake, tail lights, turn signals do not work either side...they all worked before repair..fuel gauge not working either (can’t recall if gas gauge worked before but I think it did) but gauges and clock just rebuilt also by Palo Alto Speedometer...however, emergency flashers work both sides and left and right side rear side markers work, just no turn, brake, or tail lights..checked and replaced all bulbs, checked fuse 5, it was ok...rotated fuse and cleaned fuse connector..still no luck.

Suggestions next? Seems to be power at driver rear bulb socket as flashers work? Not likely a short in wiring leading to rear under door threshold as flashers work both side?...the non MB tech suggests I replace left rear socket holder (expensive part and hard to find without buying whole light assembly) as he thought it also controlled right lights? Seems hard to believe it could be socket holder as flashers work and side marker lights work..

Thanks in advance...great and informative site, been a reader for years and just finally joined as full member

[GM]

Recommend you look at all the fuses.

[Ghowe]

Thanks for suggestion....forgot to mentioned I already checked and cleaned contacts on all fuses..all good

[66andBlue]

Do you know what was disconnected under the dash during the repair process, for example, any handshake connectors?
https://www.sl113.org/wiki/Electrical/FlasherRelay
Also take a look at the wiring diagram and you'll see that the suggestion by the technician can't be the solution.
https://www.sl113.org/wiki/Restricted/ColorWiringDiagrams

[Ghowe]

Thanks! I’ll check that to see what tech did when he hooked connectors back together after repairs..if mixed up, would emergency flashers work? Guide to which connector goes to which? Is this the connectors under driver side  dash ?

[Peter van Es]

If you open up one of the black bakelite-like connectors you can see it is easy to move the contact pins around, or swap them over. That may have happened. Weird and wonderful things happen when that is the case.

See: https://www.sl113.org/wiki/Electrical/Connectors

[114015]

Ghowe...,

If you haven't unplugged any of the connectors (the one for the taillights including fuelpump is located close to the left kickpanel) then those aren't the reason for non-working functions.

Yes, you can theoretically exchange the both 12-connector plugs under the dash that are for the turnsignal switch and the center instruments cluster. However, they are oriented the opposite direction with their harnesses (if I rmember that correctly) and the male and female plug for the turnsignal switch have a little red "bands" around the harness, close to the plugs...

Sounds to me that the taillight assemblies are not properly grounded. Have you checked the little brown ground wires that go from each of the both plugs for the taillight assemblies ?

Achim
(with 'some' experience on the wiring harness)

[Ghowe]

Thanks for the tip!...will definitely check that out also...

[Ghowe]

Will also check that out again as I thought tech checked all ground...I’m just confused why flashers work both sides and rear side markers work, which would indicate that the bulb socket assembly is grounded properly? Yet, the brake, turn, taillights don’t work?! Is it possible the build assembly is bad and part of it works? Does the left rear bulb assembly power the right rear so that if left side bad, nothing on right side works (except emergency flashers!)? Or since flashers work both sides, then right side getting power?

Thanks to all for any help! I’m open for any suggestion as reluctant to buy expensive  left bulb assembly and then that not be the problem...a little concerned tech wants to just change a part thinking that will do it when all was working before repair...can’t help thinking something tech missed when reassembled that’s causing problems...

[66andBlue]

More questions:
1. Do the front turn signals work?
2. Was the connector number 46 shown in the wiring diagram disconnected?
Take a close look at that connector (https://www.sl113.org/wiki/uploads/Restricted/280sl.jpg).
 
The black/white wire goes to the left tail light (number 49), 49a is the turn signal.
The black/green wire goes to 48a, the turn signal in the right tail light (not shown in my screen shot).
Check whether that wire inside the plug on the right tail light gets voltage when you select the right turn signal.
If yes, then check the grounding of the right tail light.
If no, then check connector number 46.

[Ghowe]

Front turn signals do not work...you’ve given me great ideas to work with...I’ll be on your checklist Monday when I’m back in town to go “hands on”on car...thanks for excellent input...with this forum and all its help from participants, we’ll get this problem solved! I just can’t get over that flashers and side marker lites work but nothing else! Gremlins abound!

[66andBlue]

You wrote that you have a 71 280SL. Is it really that late or just registered in 1971? Manual shift or automatic?
What are the last five numbers of your VIN? You can check its manufacturing date here:
https://www.sl113.org/wiki/DataCard/USModelYear

What kind of hazard flasher is installed, the electronic illuminated one? See:
https://www.sl113.org/wiki/Electrical/HazardWarningLights

The original owners manual for the car includes a wiring diagram for the car that can also help you or your mechanic finding the gremlins.
Do you have it?
Also just to make sure, when you test the tail lights and turn signals your ignition key and the light switch are in the correct position?
https://www.sl113.org/wiki/Electrical/Lightswitch

Good luck and let us know what you find on Monday.

[Ghowe]

21244...title says 1971..automatic...illuminated switch...have original owners manual and wiring diagram..tested with engine on and off and key in all positions...headlights worked, high and low, in all tests..thoughts on whether it could just be the left rear bulb holder assembly, as tech suggested, even though both right and left flashers and left rear side light worked?

[lpeterssen]

Dear friend

Check connections at the footwell driver side on the 12 pin connector that interconnects with rear wiring harness.  Your problem is there.

Take a multimeter in hand and the wiring diagram published here and start checking each of the cables. Attached a photo of the order on which they should be on the connector. That sudden change seems to me somebody disassembled it and placed the pins in the wrong order.

The photo attached is for the female connector which is screwed on the foot well. The male connector that comes from main harness should match those positions inversely.

Enjoy your Sherlock Holmes work.

Best regards
L.peterssen

Ps if you need a wire harness rebuilt service, I am the guy you were looking for.

[Ghowe]

Thanks for the great tip! When I get hands on tomorrow, I’ll definitely check this first as it all worked before heater levers replaced and instruments with new bulbs installed (all dash lites and heater lites work)..seems likely, as you said, they did something wrong when reattaching connector..Gary

[Ghowe]

Update to all...gave tech all your great suggestions and he pretty much said he already tried all those (don’t really believe he did) and now says it’s beyond their capability and can’t fix it...this is after they installed rebuilt gauges (now working) with new bulbs and installed new heater levers (all work), new speaker, and fixed low beam on drivers side that would not work only on high beams...now beyond capability?...I think, since they were already paid for that and knew lights all worked when brought in, they not want to spend any more time trying to figure it out because it would be on their “dime” as they most likely originated the current problem when they took the dash apart...I’m just wondering what they did behind the dash to make rear lights not work that may now require opening up the dash again?...

It’s all so frustrating...so I think I’m going to have to tow it home (runs great but no brake lites!), methodically go thru all of your suggestions, and if I can’t find it on my own with your great tips, find  another tech...does anyone know “the guy” for these old Mercedes in the Naples/Ft Myers/Sarasota Florida area?  I need an old school Mercedes guy on this...

Open to any and all suggestions as I’m a little frustrated...thanks all for your great tips and assistance! Gary

[66andBlue]

...does anyone know “the guy” for these old Mercedes in the Naples/Ft Myers/Sarasota Florida area?  I need an old school Mercedes guy on this...

Is Titusville too far away for you?
Pierre Hedary comes highly recommended by several members here, give him a call.
http://www.pierrehedaryandco.com

You might want to get a list together of all the lights that do not work and those that work. If I understand your comments correctly it is not just the rear turn signal lights but also the front ones. Plus brake light. What about parking lights from and back, license plate light?
In other words all the lights mentioned here:

[Ghowe]

Thanks for the info...I will check each and every light when I have vehicle back in my possession and post results...Titusville is about 220 miles away....I may make a “shopping list”  of every little nuisance and arrange to ship it up there...

Also, Miami, Lauderdale, West Palm is about 100 miles away...any suggestions for “the guy” anywhere in that Southeast coast Florida area?  Thanks again to all!