Headlight switch failure, view inside

[zentoed]

I just replaced a headlight switch and couldn't resist opening up the old one to see what was making the castanet noises.
From what I can deduct it looks the failure is isolated to the upper plastic piece whose function is to supply the detents to stop the switch in the correct positions.
When this very thin plastic deteriorates the pieces can drop down into to switching part of the mechanism and create all kinds of havoc.

 

[gerryvz]

I just replaced a headlight switch and couldn't resist opening up the old one to see what was making the castanet noises.
From what I can deduct it looks the failure is isolated to the upper plastic piece whose function is to supply the detents to stop the switch in the correct positions.
When this very thin plastic deteriorates the pieces can drop down into to switching part of the mechanism and create all kinds of havoc.




View attachment 137768

Totally agree. See more on the topic here…

HOW-TO: Replacing W124 interior headlight switch | "HOW-TO" Tutorial Articles

My 1994 E500 headlight switch started getting finicky, sometimes stuck, and telling me it needs to be replaced. There is a fantastic HOW-TO at Pelican Parts: LINK HERE: Mercedes-Benz W124 Headlight Switch Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article A couple of...

www.500eboard.co

HOW-TO: Replace Early W463 Headlight Switch | G-Wagen Models

Early W463 G-wagen models, from 1990 through about 2000, share their headlight switches with MB sedan models such as the W124, 202, and so forth. This is the standard round switch with the pull-off knob, foglight indicator light in the center, and so forth. With age and sometimes use, these...

www.500eboard.co

 

[zentoed]

I should have known that there were already pictures of failed switches if I only looked hard enough

 

[speedy300dturbo]

This seems to be an increasingly common failure as these cars get older. I wonder if failure of the plastic parts is due to heat related fatigue, as the headlights are wired in a pretty old-school way (compared to modern cars) with battery power running directly to the switch. Much of the load at the switch (and resulting heat) can be redirected by using SPDT relays in the headlight circuit. A must-do if you're running high powered (overwattage) halogen bulbs

 

[gsxr]

Up until a few years ago I had been replacing failed headlight rotary switches with good used ones... then, the used replacements would fail in short order.

Now I just shell out for new. As you discovered, the plastic just doesn't hold up after 30 years. Thankfully these are still available and not terribly expensive, and should be a once-per-ownership expense.

 

[gerryvz]

Heat and age and to some extent, use, ends up making the internal detent plastic brittle, and eventually crack. This is one item you should just purchase new from MB via one of the discount dealers.

My switch in my E500 is just beginning to get slightly "sticky" or notchy, so I'll be putting a new switch on my next parts order.

 

[TerryA]

It seems that we will be having a lot of plastic and rubber failures as our E500Es age.

My light switch failed a few years back. I had it replaced w/ a brand new one.

 

[gsxr]

Guess what happened a couple days ago in one of my cars? Yep, the detents are screwed up! Another headlight switch to replace...

 

[maw1124]

Yeah, I’ve done this once with a new OEM switch… and lately (less than 30k miles later), it feels just like the one I replaced… I’m not sure what gives on that one.

maw

 

[northNH]

FWIW Several years ago, after consideration of past experience and some simple calculation, I upgraded two of my 124s to 100/80W bulbs. I neither altered the original wiring nor installed any relays.

Since then, plenty of light, zero blown (10A) fuses, no headlight switch replacements…

 

[maw1124]

Yeah…I think mine are 55w… PM me if you have time on those calculations… IIRC mine got new ballasts when that was done… but I’m on US spec ‘92 headlights so maybe they can’t handle 80w… I recall 55w (super white) being as high as my guys wanted to go... car has been fine since, so I haven’t fussed with it anymore.

maw

 

[northNH]

Watts/Volts = Amps

100/~13 = 8A
80/~13 = 6A
60/~13 = 5A

They would be a bit brighter with relays delivering direct system voltage (13.4ish vs 12.6ish)
But apparently no safer…

 

[Jlaa]

Yeah, I’ve done this once with a new OEM switch… and lately (less than 30k miles later), it feels just like the one I replaced… I’m not sure what gives on that one.

maw

I did this too. I replaced my original HL switch in 2018 I believe it was and then replaced the replacement in 2020. The second go around was very quick!

 

[gsxr]

I did this too. I replaced my original HL switch in 2018 I believe it was and then replaced the replacement in 2020. The second go around was very quick!

Whaaa...!?? How many on/off cycles could that have been, since you don't daily drive it?

 

[Jlaa]

Whaaa...!?? How many on/off cycles could that have been, since you don't daily drive it?

Approximately one trillion cycles from testing NA vs Euro N7 BOW relays, then testing Stribel vs Hella N7s, then testing my modifications to both, then with LED bulbs.

 

[maw1124]

And what did you settle upon, @Jlaa?

maw

 

[Jlaa]

And what did you settle upon, @Jlaa?

maw

Heh. Euro Stribel N7 BOW relay + modifications allows you to use an LED in the CHMSL to prevent CHMSL housing melting and avoid "bulb out warning" messages on the dashboard. Particularly useful since new CHMSL gear is mostly NLA.

HOW-TO: Prevent 3rd brake light (CHMSL) from melting by using a European-spec N7 Bulb Out Warning Relay and an LED | "HOW-TO" Tutorial Articles

What this modification does: It allows you to run a low-heat LED in your CHMSL without tripping the bulb out warning indicator on US market E500Es. Side effects of this modification: Your rear sidemarker lights will cease to function. Workarounds to the side effects: There are three...

www.500eboard.co

 

[sheward]

My new headlight switch is available to be picked up at the local dealer. This will be for the 60,000 mile car. Like the mirror, I think it's mainly a plastic/time issue.

drew

 

[sheward]

For the record, the headlight switch I received came from inventory in Florida. Made in Italy.

drew

 

[maw1124]

Yeah, I’ve done this once with a new OEM switch… and lately (less than 30k miles later), it feels just like the one I replaced… I’m not sure what gives on that one.

maw

Well, it looks like I need another one. I don’t know if it’s just the knob or the switch mechanism behind it, and can use some help. The symptoms are (1) less notchiness between selections; and (2) the fog light function is busted… when I pull the knob out for fog light application, it doesn’t notch and hold and the spring pulls the knob back in. It‘s a bit of a pain because the car certainly isn’t driven daily and almost never at night (though I do often run parking indicators with fogs at dusk — beach runs for sunset, Golden Hour, all that fun stuff). I may just have the fogs wired to come on whenever the parking lights are engaged, although I‘m a bit loathe to do so.

It would be nice to give clear direction on what needs changing. If it’s just the knob, I’ll buy one and put it on myself, but if it’s the switch, well, then not. TIA.

Cheers,

maw

 

[Jlaa]

Well, it looks like I need another one. I don’t know if it’s just the knob or the switch mechanism behind it, and can use some help. The symptoms are (1) less notchiness between selections; and (2) the fog light function is busted… when I pull the knob out for fog light application, it doesn’t notch and hold and the spring pulls the knob back in. It‘s a bit of a pain because the car certainly isn’t driven daily and almost never at night (though I do often run parking indicators with fogs at dusk — beach runs for sunset, Golden Hour, all that fun stuff). I may just have the fogs wired to come on whenever the parking lights are engaged, although I‘m a bit loathe to do so.

It would be nice to give clear direction on what needs changing. If it’s just the knob, I’ll buy one and put it on myself, but if it’s the switch, well, then not. TIA.

Cheers,

maw

99% sure this is the switch w deteriorated plastic inside, not the knob. Sorry. I had to replace a lightly used switch after approx 2 years as well. Crappy kwality.

 

[maw1124]

99% sure this is the switch w deteriorated plastic inside, not the knob. Sorry. I had to replace a lightly used switch after approx 2 years as well. Crappy kwality.

Well at least I keep my arrow knob…… not sure when I’ll get around to this, but we’ll see.

This part? 6288-01164259

maw