Head Lamp Wiring

[Rolf]

I am beside myself with this one. The lighting for the parking, directional and fog lights, on the right side of the car, was crossed. The parking light blinked instead of the blinker light, the parking light came on as suppose to. The fog light didn't come on at all. All of the lights on the left are working correctly. I took the headdoor apart and checked out the circuits and the bulbs. the bulbs are fine but the circuit was messed up. I got the connections to where they are suppose to be. Everything worked properly except for the fog light. I checked the voltage and got 12+ for the connection. When I connected it to the fog light the voltage went to zero and the fog light did not work. I took the wire for the parking light and tested the fog light, which then worked. I don't understand how I can get 12+ volts from the fog light wire and then connect it and get zero. I have been tearing what little hair I have out trying to figure this out. Thank You.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[al_lieffring]

Rolf

Check the ground (brown)wire at the bottom of the headlight bucket.
Remove the bolt that attaches the wire to the body and clean off all corrosion.
The ground might be good enough to run the low watt bulbs, but not the higher wattage fog lamp bulb.


66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[Rolf]

Al,

  I did that. The fog light does work when I connect the parking light wire to it. I get 12 volts from the fog light wire but It does light the bulb. When I check for voltage on the fog light wire, connected, I get zero volts, although I get 12 when it;s not connected.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[al_lieffring]

quote:Originally posted by Rolf

Al,

  I did that. The fog light does work when I connect the parking light wire to it. I get 12 volts from the fog light wire but It does light the bulb. When I check for voltage on the fog light wire, connected, I get zero volts, although I get 12 when it;s not connected.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

On my 66 there is an accesory fuse box on the washer bottle and clutch resivior bracket. This is the fuse for the fog lights. Check the connections here too.

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[Rolf]

Thank you Al, I had no idea what that box was for. I removed the cover and discovered a fuse inside which was good. I changed it anyway because I had no idea how old it was. I do get 12volts to the right hand foglight, yet it still does not light up. The lefthand one does. I even took the right one and tried it on the left side. It works there but not on the left. I also took some sandpaper to the area where the ground screw is and to no avail. The right hand foglight does light up when I connect it to the parking light connection. I am totally puzzled.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[al_lieffring]

quote:Originally posted by Rolf

Thank you Al, I had no idea what that box was for. I removed the cover and discovered a fuse inside which was good. I changed it anyway because I had no idea how old it was. I do get 12volts to the right hand foglight, yet it still does not light up. The lefthand one does. I even took the right one and tried it on the left side. It works there but not on the left. I also took some sandpaper to the area where the ground screw is and to no avail. The right hand foglight does light up when I connect it to the parking light connection. I am totally puzzled.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

Rolf I find it easier to check curcuits with an incandescant (not an LED) test light attached to ground instead of a voltage meeter. A volt meter can not distinguish between a live wire, a circuit with high resistance or a feed-back through a circuit with an open ground. With no load a circuit with high resistance or a feed-back will show 12 volts on a meter, but when a load is put on that circuit, the voltage will drop to 0.

Take apart the connectors on both front head lamp doors and check all the circuits one at a time with a test lamp, I'll bet there are two crossed connections, they may not necessarily be in the lamp that is acting up.

Al



66 230sl
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[Rolf]

OK Al I'll give that a try. The connection for the right fog light is acting exactly the way you described it.

Rolf
1966 230SL Auto
1992 300D
1991 FLHS