Indicator Light woes

[Peter van Es]

Dear all,

I’m wondering how many of you have had weird electrical problems and if there is someone who can help me. Also, I apologize ahead of time for the length of this post. First, let me start with the facts:

• I have an SL in which the US headlights were replaced by European style headlights (2 years ago)
• About a month ago I had some bodywork done, the side-markers removed and the car repainted
• As I drove the car away from the garage, the indicator relay stopped working after three turns, when waiting for a traffic light, indicating left (relay got very hot, burning smell in the car – as the relay is mounted under the dashboard)
• I replaced the blinker relay with a new relay (more modern) and it seemed that everything was fine.
• However, after a long drive I noticed similar problems… blinker relay got very hot, left indicator stopped working. Right indicator was ok. Relay did not break permanently as it appears to be sturdier than the original model it replaced.

Now for my diagnosis and analysis and this is where conjecture comes in to it.

I first suspected that the removal of the side-markers may have had something to do with this. Inspection and checking the tail-light and headlight assemblies showed this not to be the case.

I narrowed it down to the left front headlight assembly. I removed it and when the assembly is out of the car, everything works fine (indicator, relay does not get hot etc). I usually suspect bad ground leads in this case, or faulty wiring in the cable coming through the fender to the headlight assembly. I checked it all carefully, cleaned the contacts etc. Then I reinserted the headlight in the car, and noticed that the blinker stopped working when I moved the assembly straight up to the fender. In fact, when trying to screw it in, sparks would appear at the lower left screw.

So in essence 12v was available on the metal headlight assembly surround, leading to a short when inserted in the car. I think that this points to a faulty ground connection, or a short on the headlight assembly. I initially tried some duct tape taped to the inside of the light receptacle in the fender to prevent shorts there… but that did not work.

I could also see that the metal headlight frame has some “corrosion” on the inside of the frame… or oxidization, I do not know how to describe it exactly, but it does look like there has been an electrical process going on for a long time at that point (which immediately made me think…. And what does a current at that point do for rust around the headlights… where many of our cars suffer it commonly). The rubber ring was fused to the metal too at that point… probably because of constant current.

I then had a look at the light-assembly on the right hand side. When the blinker was blinking, I could not detect 12v on the light-assembly metal frame. I removed that assembly to compare it with the one on the left hand side. When I did, I could see that the wiring loom had been spliced in the right hand fender, and an additional ground wire had been connected between the connector ground wire that attaches to the assembly, and the metal of the fender.

I drew the conclusion that after painting the right and left light assemblies had been reversed, leading to this indicator problem, and that a previous owner had solved this problem by improving the grounding.

So I switched the headlight assemblies, went through the procedure of inserting the assemblies with the blinker on (to see if shorting would happen again). At this point the light assembly fell out of the fender (don’t ask !) so now I have scratches again on the paintwork under the headlight, @#*~!

Initially that appeared to do the job. I tightened the assembly in the fender, and then went on a little shakedown drive (nothing like driving a few speedbumps here in Holland to ensure that all contacts get made or loosened, as required). And after 15 minutes, the same indicator problem appears again, but this time on the right hand side of the car (i.e. the same light assembly, as I switched them).

Again… no blinking signal, as it is shorted. The flasher relay gets very hot. The green indicator light dims when indicating.

I used an ohm meter to probe the assembly. The problem is that the blinker light is of course providing a permanent connection (with a resistance of only a couple of ohms) so it is very hard to find if there is a short on the assembly, but as far as I can tell there is not.

Now here are my questions – for everyone who knows more about this, or as had similar problems…
 

• what do I do next to solve this?
• Is the headlight assembly meant to be isolated from the fender (through the rubber at the back – which I assumed was for mechanical protection only) through the use of isolated screws?
• has anyone else verified their headlight assembly for voltage and current…
   
• has anyone any ideas on the effect of corrosion / rust of such an electrical current?

Any help will be much appreciated

Peter van Es



Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[waqas]

Good detective work so far (sorry about your paint).

I suspect the problem is with the path of the positive blinker wire. There are only three places where this wire can be shorted to ground on the assembly (assuming it IS the assembly at fault, which you seem to have verified):

• The connection to the blinker-bulb
• The wire going from the blinker bulb to the main connector assembly
• The main connector assembly

First, I would lift up the sprung-metal positive contact to the blinker light bulb and then try to measure continuity (using the ohm-meter) with the assembly removed, of course. If there is a short to the frame (between the wire or the main connector), it should show up. If not, then the point of contact at the bulb is suspect (it may be shorting to ground in a very subtle way, eg. around the bulb base). I would inspect that area closely.

Next, (if the short is indeed upstream of the blinker bulb) unscrew the connector assembly from the frame and inspect the turn-signal solder/connector for something obvious. (or very closely-spaced loose wires)

Sometimes, wire insulation is cracked and only 'opens up' when the wire is bent (under pressure: headlight placed in fender socket)... so I would closely inspect the blinker positive wire along the entire length from connector to bulb base.

I'm not sure I can help beyond this, but keep us updated and I'll try!

WAQAS in Austin, Texas

[rwmastel]

I'm no electicial engineer, but the simplest thing to do is ensure you have the correct bulb in that troublesome assembly.  I'm sure Waqas is leading you down a better path, but the bulb was not mentioned in your troubleshooting.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[waltklatt]

Peter,
Sorry to hear of your trouble with the paint.  Maybe a little touch up paint will work there.  
I would remove the little dim light that illuminates the main beam bulb holder.  Think the problem lies in there.  Then isolate the contact from there and recheck the blinker.  I grabbed your picture and added some red circles.  Look at these areas and see if there are stray wires or so coming out.  Also tuck in the two wires from the blinker to the socket at the bottom.  Wires should be snug inside a small channel running around the main bulb holder.  
There should be no sparks coming out from anywhere.  
If there are sparks then the ground connection is weak, and is trying to ground where the sparks are.  Or you have a positive feed to the headlight assembly.  
Another thing to check is the plug prong order on the socket from the body to the headlight, maybe the wire order is incorrect.  Sometimes, and it does happens, when pulling the plugs off, the back locking cover pops off and the wires pull out.  So check the wire order again.  
Hope this helps and let us know of your misses/success.
Walter
1967 220SL-diesel  

Download Attachment: 20077644748_LightAssembly.jpg
59.96 KB

[Peter van Es]

Dear Waqas, Rodd and Walter,

I’ve continued on my search, but so far with no results.

The indicator light is a 12v 15W type. It is a little less powerful than the 18W normally used for indicator lights, but that just helps to reduce the current.

I pulled up the old formulas R = U / I (i.e. resistance is voltage divided by current) and P = U * I (power is voltage times current) to derive that a 12v 15W lamp leads to a current of 1.25 A (enough for sparks) at a resistance of 9.6 Ohms.

The bulb, out of the assembly, measures indeed at around 10 Ohms. When the bulb is out, I measure infinite resistance (i.e. no short) between the metal frame of the assembly and the positive terminal of the indicator light.

I then checked the connectors on the main connector assembly. The ground wire shows a proper, zero resistance connection to ground measured anywhere else on the car. All other wires look correct, and, as I wrote before when the assembly is out of the fender, everything works fine! I bent the white and brown indicator wires on the assembly (to check for cracks) and inspected everything else as Waqas suggested, but could find nothing.

I did look at the little dim light that illuminates the main bulb holder… I’d never even spotted that thing, Walter. It was inserted incorrectly (at least I assume that the two bajonet posts should fit on the extruding holder) and reinserted that light. Again, no change.

So again, in my view, theoretically it all should work, (resistance between +ve wire and assembly frame around 10 ohms), and it should work when inserted into fender… and it does work, right until I tighten the screws… and then the sparks reappear, the blinker relay is overloaded and then: nothing.

I AM GOING CRAZY! HELP!!

Peter


Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[rwmastel]

quote:Originally posted by vanesp

… and it does work, right until I tighten the screws… and then the sparks reappear, the blinker relay is overloaded and then: nothing.

Is there a rouge wire tucked behind the head light bucket where the screws go into the body?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[enochbell]

Rod,

Is that rouge or rogue?  Bid difference  

g

'64 230sl, fully sorted out...ooops, spoke too soon

[Jonny B]

Peter,

This sounds similar to a problem I had with the rear license plate lights. I saw that they were out, and checked the fuse, etc. When the lights were sitting in the trunk (not screwed into the body) they were fine, the second I tried to put them in place, a flash of spark and the fuse blew. I even tried using the black electrical tape to isolate them from the body metal, no luck. The problem turned out to be a crossed wire in the connector, current was shorting out since it was not supposed to be there in the first place! In your post you indicated you checked the connection, could a pin have been misplaced during the indicator light removal process??

Jonny B
1967 250SL Auto

[waltklatt]

quote:Originally posted by waltklatt

 
Another thing to check is the plug prong order on the socket from the body to the headlight, maybe the wire order is incorrect.  Sometimes, and it does happens, when pulling the plugs off, the back locking cover pops off and the wires pull out.  So check the wire order again.  

Peter, I would check the wire prong connector plug on the body, not the headlight.  Check the wire order to make sure it is correct.  See the previous posting, copied above.
I'm certain one of the wires for the blinker is crossing over.
Walter
1967 220SL-diesel

[Peter van Es]

Walter,

I'll check the order again -- if someone can give me the correct order. I seem to have mislaid my colour coded wiring diagram -- at least I can't find it anywhere.

As one of the brown connectors is damaged (same previous owner that put in the extra ground wire) I'm ordering new ones from SLS as we speak. Also, someone else suggested that in order to eliminate bad ground connections, to just (temporarily) run a ground cable straight from the battery -ve pole to the headlight assembly. That seemed like a good suggestion too...

So, if anyone can help me with the correct order of wires (and colours) for the arrangement:

Code: [Select]

(seen from the top with cover off the connector)

               x
          x    x
          x    x
I'd be much obliged... also, I noticed there are white/green and grey/green wires involved....

Thanks

Peter

Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[waqas]

Could you possibly compare one assembly to the other to get the correct order?

WAQAS in Austin, Texas

[Peter van Es]

I would compare one assembly to the other, if it would help. But remember that the same light assembly failed in both the left and the right hand fender. Both are wired up the same way. Since the failure happens on both sides, I cannot use this as the reference. So if someone could have a look and tell me what it should be, I would appreciate it.

One of the plugs is cracked however, so I am ordering new plugs to attach to the wire harness. That way at least I'm sure of the connections. For this I do need the correct wiring order.

Peter

Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL

[rwmastel]

quote:Originally posted by vanesp

But remember that the same light assembly failed in both the left and the right hand fender. Both are wired up the same way.

So, doesn't this tell us that the fault must be in the head light assembly?  If wiring on the "body" side of the connection was wrong in both fenders, then both head lights would have a problem.

Also, I was reading another old thread where I mentioned head light seals to someone else.  Do you have all the seals?  There's one between the glass lense and the head light assembly, and antoher one between the assembly and the fender/body.  Maybe this seal not only keeps the water out from behind the assembly, but also electrically isolates the assembly from the body?

quote:Originally posted by enochbell

Is that rouge or rogue?  Bid difference  

Greg,
Are we at an auction or something?  How much did you bid?  I guess we both have typing errors!  

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[waqas]

I think the seals are only for moisture protection. When I got my car, the European lights had no seals at all... so both my headlights would have been shorting like crazy!

I would compare the wiring order in the harness connector on the headlight assembly itself (male end), on both headlights since one is apparently functional, and also make sure there are no stray wires hovering around.

WAQAS in Austin, Texas

[J. Huber]

Peter. Here you go: looking at the bakelite box from above. tell me if this makes sense.

X Green/Grey stripe

X Green ----- X Red/Grey stripe

X Doubled-up Red ----- X Green/Black stripe

PS. Are the "bakelite boxes" available and sold separately from wiring? A couple of mine are busted. Thanks.

James
63 230SL

[Peter van Es]

quote:Are the "bakelite boxes" available and sold separately from wiring? A couple of mine are busted.

Yes, SLS in Germany sells them. http://www.sls-hh-catalogue.de/start/index.phtml?lan=2

Peter

Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280SL

[Peter van Es]

Well all,

After my return from holidays I have finally solved my problems with the indicators. In time honoured tradition (NOT) I have decided to complete this post, to share my experiences.

When I started looking at the connection colours James so graciously posted in response to my request, it took a while for me to figure out that the right and the left headlight assembly actuall have different colours... and since I could not find my coloured wiring diagram that was sent with Pagoda World version 7 anywhere, there was nothing left but for me to take my old multimeter and measure and reason my way out of this mess.

A bit of sleuthing later I came to the following (note, you can also ensure fixed width text in your post by using the "Insert Code" button in the editor (with the # button) and then typing your text).

Code: [Select]

Lighting unit right
X    0   grey/green (to light switch)
grey/red (parking)      0    0   green(white) (side-marker)
black/green (blinker) 0    0   brown (2x, ground and ground of assembly)
--YY--
 ||



Lighting unit left

X    0   grey/green (to light switch)
grey/black (parking)    0    0   green/black (side-marker)
black/white (blinker) 0    0   brown (2x, ground and ground of assembly)
--YY--
 ||
Once I figured this, I noticed that the mechanics had completely wired up both assemblies wrongly. Because the sidemarkers had disappeared during the bodywork and paint job, and because the tiny parking lights are not very noticeable or important anyway, this only showed itself in the important indicator/blinker lights. Essentially of the bottom terminal the ground (brown) and blinker wires were inserted on the wrong side of the assembly.

Out of the car this works fine, and in the car, the blinker relay shorts out and breaks. I've replaced the blinker relay, bought new bakelite boxes, and rewired the plugs correctly. I still need to replace the broken alarm generator switch... which is a pain to do as it is below the speedo assembly.

Anyway, good luck if you also have wiring problems.

Peter


Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280SL