My headlights are wigging out....

[Hartge330ci]

So I bought the car, a 300D about 3 weeks ago and neither headlight was working, only the foglights worked. I replaced the headlights about a week ago and they worked. Tonight I turned on the lights and the headlights worked, but both foglights, which were working last night were dead. I get to work and start playing around with the switch by turning the lights and and off, and now only the driver side headlight works. Both high beams still wor. What is going on here? Any ideas?

[jt20]

I have been struggling with this as well.

Go over all your grounds to body and check your pins to headlight as well as blinkers.

Replace as many fuses as possible! while cleaning all!! the contact surfaces in the fusebox.

thats a start.

[SD Blue]

Ditto the ground check but it sounds like the headlight switch is acting up, especially since only the lights are affected. You might be able to spray it with contact cleaner (disconn. the battery first) and get it to work. I believe the rotary switch is fairly pricey ~$100+

[Hartge330ci]

Seems weird though because the headlights initially were definately broken. I tested the headlight at the connector and there was power. Would a faulty headlight switch cause headlights to burn out?

[jt20]

Originally Posted by SD Blue

Ditto the ground check but it sounds like the headlight switch is acting up, especially since only the lights are affected. You might be able to spray it with contact cleaner (disconn. the battery first) and get it to work. I believe the rotary switch is fairly pricey ~$100+

What happens inside the switch that causes the issues? Its a pretty simple switch, correct?

[Hartge330ci]

How do I get the headlight switch out?

[jt20]

the knob pulls straight out then there is a nut behind it. Undo that, then I believe it pulls out from the back.

[jt20]

21 or 22mm i forget

[Hartge330ci]

Does anyone have a schematic of which terminal on the main headlight switch powers which light?

[KarTek]

Originally Posted by Hartge330ci

Seems weird though because the headlights initially were definately broken. I tested the headlight at the connector and there was power. Would a faulty headlight switch cause headlights to burn out?

Keep in mind that reading power on an open connector is meaningless for the most part. Test electrical circuits across the load.

You can do this with lights be having the lamp plugged in, then touching the probe to the terminal you wish to test.

[SD Blue]

Originally Posted by Hartge330ci

Does anyone have a schematic of which terminal on the main headlight switch powers which light?

I believe the schematic for that particular car (depending on the year, which you didn't mention) is available in the Haynes manual.

[Hartge330ci]

I tested it at the lights.
At this point only the driver side low beam and high beam work and only the passenger side high beam works. This is where I am also getting power on the meter. No power on the meter anywhere else. Now, I am assuming since both headlights are powered together at the headlight switch, the headlight switch cannot be the culprit, correct? I would assume the same holds true for the headlight fuse, correct? So where could my problem be. The passenger side low beam and both fogs actually died at the same time, not at seperate times as I thought earlier.

[jt20]

have you changed the Pass low beam/ fog fuse yet. All of those symptoms point to the same circuit, it will be something very simple. 8 times out of 11

[Hartge330ci]

Are the fuses for each side seperate or is it all one fuse. I haven't changed fuses yet because I don't know where to buy those funky fuses.

[jt20]

I have trouble finding good replacements as well. There is a fuse for each side. But my fogs went out along with one low beam (pass) and replacing a good looking fuse fixed it.

go fig