low beam headlight problem

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low beam headlight problem

Postby Richard55 » Thu Dec 27, 2012 8:30 am

Now that the days are getting shorter I actually tried using the headlights and found a new problem. The low beams do not work and the high beam switch on the turn signal stalk just does a flash-to-pass type behavior and they turn off as soon as I let go. I got stuck out in the dark the other night and had to quickly rig something up with a tubing clamp to hold down the high beam switch to keep them on so I could drive home. Fortunately the high beams aren't super bright like a modern car with HIDs so no oncoming drivers seemed to care.

I'm pretty sure they were working properly when I bought it and I could toggle between low and high beams which would rule out a problem with incorrect wiring. That was in the summer so I never really tried them again after my initial checking of everything before finalizing the purchase.

So essentially I have:
-First headlight switch detent - Parking/city lights on. Gauges light up and can be dimmed properly.
-Second headlight switch detent - same as first, just parking/city lights
-While holding the high beam switch - High beams on
-Without holding the high beam switch - No lights or parking lights depending on the headlight switch setting.

All fuses are good. Connections on the back of the headlights themselves are clean and solid. I found the relay under the dash and I may swap the low and high beam wires on the relay just to rule out something trivial like both low beams burning out simultaneously. Any ideas of where to start debugging or common parts to fail? How is it wired to allow the toggling between high and low beams to be sticky as it seems like that may be a clue with the behavior? Could something be bad in the connection to the key and maybe parking lights and flash to pass are separate from the key so they still work?
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Re: low beam headlight problem

Postby Richard55 » Thu Dec 27, 2012 2:06 pm

I swapped the wires to 56a and 56b on the relay and the low beam bulbs and wires are good. I'm guessing at this point it is an issue with the relay itself and will just pick up a new VW 111 941 583 and see what happens.

I figured out a lot in the process. It looks like a lot of Cobra replicas use the same dimmer relay and I found some wiring diagrams on one of their sites that helped while I was poking around under the dash.
http://www.erareplicas.com/427man/wiring/signal.htm

I believe the connections are the same on my 550.
30 - Constant +12v power
56 - Switched +12v from the headlight switch
S - Momentary switch to ground on turn signal stalk
56a - High beam filament (I may have this swapped with low, need to double check)
56b - Low beam filament

The only other possibility I can think of is if the headlight switch was bad and the switched +12v to connection 56 was never coming on. I really wish my old multimeter hadn't died. Time to pick up a new one.
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Re: low beam headlight problem

Postby Richard55 » Fri Dec 28, 2012 3:16 pm

I built a test light out of an old turn signal bulb and the leads from my broken multimeter. All the +12v lines are good and the outputs never made contact proving it was the relay (VW part 111 941 583). Since it was broken anyway I took it apart to figure out how it worked.

Image

The flash to pass is the set of contacts at the top that are directly moved by the magnet. It pretty much can't fail.

The set of contacts on the left are the set from output of the headlight switch to toggle between low and high beam outputs.

The plastic pivot at the front has a metal pivot behind it. Both get contacted by that vertical arm that moves when the magnet is engaged. The mechanism of the two arms is pretty neat and latches the left set of contacts either up of down and is what gives it its "stickiness" despite being controlled by a momentary switch on the turn signal stalk. In my case the metal contacts of the left for low and high beam became disconnected from the plastic pivot. I tried to glue it back, but it fails again after a few cycles so time to just buy a new one.

Overall a fun project with my 5 year old and getting him more and more interested in working on cars and reusing the stuff we can find in his great grandfathers' tool chest.
Last edited by Richard55 on Fri Dec 28, 2012 6:49 pm, edited 1 time in total.
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Re: low beam headlight problem

Postby beck688 » Fri Dec 28, 2012 3:38 pm

My headlights work fine - but you have found a great source for an inexpensive 12v latching relay --- thank you very much It is something I have been looking for for years!
Oh sh*t -- It was rocket science!
That's how my brain works. It's not a perfect organ.
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Re: low beam headlight problem

Postby Richard55 » Fri Jan 04, 2013 9:06 pm

The relay did fix it. It wasn't terribly cheap for the OEM part manufactured in Europe, but $64.95 for the part at the VW dealer is really cheap compared to working on my Mercedes. If you are looking for a solution, all of the latching is built into this relay so all you need are constant +12v so the flash to pass works, switched +12v so your normal lights high and low work, and a momentary switch connected to ground to toggle it. The guys at the VW parts counter were real interested in what it was going into as I guess they mostly get requests for parts from cars from recent years.

While I was under the dash I decided to use one of the unused lights on the combination fuel and oil temperature gauge to be a high beam indicator. So now I have one indicator for lights on and a second indicator for high beams on. I wish I could take it to Cars and Coffee tomorrow morning now that I have it back together, but it looks like it will be cold and rainy.
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Re: low beam headlight problem

Postby steiner » Mon Jul 10, 2017 10:48 am

Exactly the problem I had! Great info. Also wiring up the in bucket parking lights to be active.
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