Electrical Riddle of the Day

[J. Huber]

Hello. So here's the deal. When I switch on headlights (euro):

Small bulbs come on in first position, followed by main lights in position 2. All normal. But then:

If I hit hi-beams (foot knob), the pass. side goes to hi-beam, the driver's side goes completely off (except small bulb).

If I hit the flash-to-pass, driver's side goes hi-beam. Pass. side stays lo.

Any guesses? ground? bulb? corroded connection?

James
63 230SL

[Naj ✝︎]

try a new bulb... :mrgreen:

naj

68 280SL

[ja17]

Hello James,

Mysterious electrical problems are usually a caused by a bad ground (earth).  Try clipping on a temporary ground jumper wire to the each headlight assembly.

Joe Alexander
Blacklick, Ohio

[Peter van Es]

I sympathise. Really, I do... read my posting on "Indicator Light Woes". I would tend to agree, bad earth connections -- or a bad bulb. Try new bulb first. If that fails, try to wire a thick wire from the battery -ve terminal to a -ve point (like the frame) of the light assembly. If then both lights come on, you've got a bad earth.

However, because of the different switches doing different things, you may have a wiring problem between the foot switch and the flash to pass feature or in the switches themselves. A lot of current goes through these devices... as no relays are used.

BTW... and if you've got the lights out anyway, could you check the wiring of the harness for the 6 (actually 5) prong plug (colour coding and position) and insert the answer here http://index.php?topic=7132. Thanks a bunch!

Peter

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

[jeffc280sl]

Spin fuse #10 in place to improve contact with the fuse block terminals.

Jeff C.
1970 280SL 4-speed

[rwmastel]

Swap right & left light bulbs and see if the problem follows the bulb.

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

[J. Huber]

Well, thanks guys. What a site. I type my question right before going to bed -- get up and have 5 great suggestions! So, after a little morning jaunt (to the dentist!  :twisted: ), I'll do some exploratory surgery... Peter, I'll see if I can solve two riddles at once!



James
63 230SL

[J. Huber]

Ok. I am mid-surgery (on the lights not my teeth!)

I began by trying new big bulb in side that goes out when I hit hi-beam. No difference. So I cleaned up the ground in the bucket. Again no change.

I decided to try same thing on other side. Again, no changes. (except the new bulbs are brighter!) Narvas. Anyway. Then I got to Jeff's idea. Spun #10. Bingo! Hi-beams now work on both sides! However, I then tried Flash to Pass. It worked on both sides, then as I tried it again it stopped working. So now I have no flash to pass... (but apparently all good on the lo/hi beams.) What would come next on that one?

And 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









James
63 230SL

[jeffc280sl]

James,

Glad to hear one problem is solved.  Wouldn't have known of the solution if I hadn't experienced the problem myself.  That's what is great about this forum.  

Try turning fuse 1.  This is the feed fuse for the flash to pass.  I suggest you clean all of the terminals on the fuses and fuse holders.  Just a little grit, etc. can cause intermittance in the contact.

Jeff C.
1970 280SL 4-speed

[J. Huber]

Well, buttoned the patient back up for now. Was one for two. The hi-beams are working now -- but no Flash to Pass anymore... That will bug me so I'd welcome any other ideas. Until then, here are a few things I learned:

1. Jeff's idea of twisting fuses is a good one -- anytime you have an electrical gremlin -- and actually as a routine maintenance item.

I should have done it first thing -- instead of pulling off my headlamp assemblies. As Joe A. and others have stated -- always try the easiest fixes first.

2. I also learned that although it is not necessary to remove the lens when changing the main headlight bulbs, if you do it is much easier to put it back on before you attach asssembly to car. (i.e. in your lap so you can push the clips over the glass rim.) In the past I would try and do it with assembly already in -- very tricky that way.



James
63 230SL