Headlight switch bulb

[cgryphon]

1982 240D

Slowly going through all of the interior bulbs getting them working again. All fuses in the under hood box are new and working.

Last two lights are:

Headlight switch bulb. The bulb is good, but no light. When is this supposed to be on? Any “hidden” fuses?

Glove box light. The bulb is good, but no light. Switch appears to be working when tested for ohm’s, but no volts. I know it’s supposed to be on when the door is open, but always, or only when the headlights are on? Again, any “hidden” fuses?

Everything I know about electricity could be written on one side of a cocktail napkin, so answer accordingly. Wiring diagrams are a mystery to me for the most part.

Thanks for the info,

Clay

[boneheaddoctor]

Originally Posted by cgryphon

1982 240D

Slowly going through all of the interior bulbs getting them working again. All fuses in the under hood box are new and working.

Last two lights are:

Headlight switch bulb. The bulb is good, but no light. When is this supposed to be on? Any “hidden” fuses?

Glove box light. The bulb is good, but no light. Switch appears to be working when tested for ohm’s, but no volts. I know it’s supposed to be on when the door is open, but always, or only when the headlights are on? Again, any “hidden” fuses?

Everything I know about electricity could be written on one side of a cocktail napkin, so answer accordingly. Wiring diagrams are a mystery to me for the most part.

Thanks for the info,

Clay

I think it has something to do with fog lights...but then it doesn't com on with either my W116 or W123 so I am baffled too.....

I think its related to some function the US cars don't have or use.

[cgryphon]

Yeah, I wondered if it was on the fog lights also. I was kinda thinking that the glove box and this light were somehow on the same circuit and the issue was related. Maybe someone else will chime in.

Anybody ever seen the light on the headlight switch work on a 123?

Is the glove box light on whenever the door is open, headlights on or not?

Thanks,

Clay

[J. R. B.]

I didn't know about this. On both of our cars the glove box lights work but nothing lights the light switch even with the fogs on. I too would like to know if it is supposed to light up. I need another thing to fix.

[cgryphon]

Originally Posted by J. R. B.

On both of our cars the glove box lights work

I'm beginning to think that the glove box light in the 123 should work with the key in at least the ACC position, so I've got an issue somewhere, as mine never comes on.

Just went out and checked the 96 C220, which has basically the same headlight switch, and bulb, as the 123. Nothing there either, in any position, so I still don't understand what the light behind the knob is there for. Does not seem very German-like to waste a whole bulb and socket like that .

The glove box light on the C220 works with key in ACC position.

Thanks for the reply, just looking for more clues. Not as interesting as an AC or Oil thread, but I've got no problems there, knock on wood.

Clay

[lrg]

I believe the glovebox light only works when the instrument lights are on, probably to prevent an accidental battery drain. I've never seen my headlight switch light on. Anyone have a european version that can tell us how their's works? My guess is that it was meant to go on with the rear foglight which the US cars don't have.

[J. R. B.]

My glove box light works only when the key is on. As soon as I get some time I'm going to investigate my light switch and see if this thing is really supposed to work. I'll get back to you if I find something out.

[boneheaddoctor]

I think the Glove box light is like a refridgerator light...it only works when the door is open...















actually I think the key needs to be on....but I'm not putting pants on to go outside and look right now.

[dmorrison]

Your glove box light goes from fuse #4 to the light bulb and then to the glove box switch which provides a ground. The glove box switch ground wire is grounded behind the instrument cluster. All those brown wires bolted to the firewall.

Your light switch does not have a bulb in the curcuit.

Dave

[pawoSD]

The bulb in the headlight switch is for the euro-fog lights option that all our us-spec car's lack....the light in the glove box only works with the key in the ACC position or beyond.....

as for the headlight switch, it was probably a lot simpler to just use the same switch on all cars and wire it differently than to deal with multiple switches and potential mistakes etc....plus the fact that likely far more cars did have the fog lights than did not.

[Johnhef]

It never made sense to me why there was a bulb in the headlamp switch. It is for the rear fog light to let you know it is on, but the US model switches were different from the euro's (or just wired different, i've never checked) in that you can turn on the front foglamps without turning on the headlights as in the 86 and up models.

[cgryphon]

Thanks for all of the responses.

Particularly helpful info on the glove box circuit from dmorrison. Thanks Dave, that’s twice, as your contribution to a vacuum thread also solved my issue with the door locks.

Particularly disturbing visual image from BHD’s response, quote “....but I'm not putting pants on” .

Many thanks to all as always,

Clay

[J. R. B.]

I pulled the knob off on both of ours this morning and neither one had a bulb in them just empty sockets. I tried bulbs in both and neither one works probably due to the wiring systems. Now I pose a question to all of the more experienced MB mechanics. Is there a way we can wire this in and make this light work? I looked at the knob and if it worked you would not only have a neat orange dot light up but also a white, triangular indicator arrow.

Originally Posted by J. R. B.

I pulled the knob off on both of ours this morning and neither one had a bulb in them just empty sockets. I tried bulbs in both and neither one works probably due to the wiring systems. Now I pose a question to all of the more experienced MB mechanics. Is there a way we can wire this in and make this light work? I looked at the knob and if it worked you would not only have a neat orange dot light up but also a white, triangular indicator arrow.

Anyone have a diagram of the switch handy?
I never thought to pull one of these out at the yard just for reference purposes.
There has to be a huge amount of connection points on the back..easy enough given enough time

[speedy300Dturbo]

Here's the deal with the headlight switches. The early US ones are "almost" the same as the Euro ones as far as the mechanical aspect of it - it can be pulled out to the second click (this turns on the rear fog on Euro cars) but nothing will happen. On the back of the switch you'll see blank space for extra male pins for the rear fog light, and the respective female pin sockets on the plug that goes into the headlight switch.