Hi, the headlights on my '92 400E stopped working today. Last time they worked was last night while driving home. When I went to drive to work this morning, before sunrise I went to turn the light switch on and nothing, no low or highbeam; except...

The foglights do work and the highbeam does work when the turn signal stalk it pulled towards the driver.

I checked to fuse and it's fine, a search of the forum didn't pull up anything.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

The DMM (Digital Multi-Meter) will tell all.

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'84 300SD sold
124.128

I had the same thing happen a year ago on an E420. Headlights only all of sudden stopped working, but all other parking, turn and fog lights were fine. Replaced Multi-function switch and all is good since.

Ok, I tested the plug at the headlights, and did a basic visual check under the hood, checking out the wires. Everything points to it being a faulty multi-function switch, which on this model is called a combination switch.

Think I'll have to pick one up, one question though; does the headlight switch every have any issues?

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

I purchased a used combination switch on ebay, I received it a couple days ago and looked it over, it's looks as if it's almost brand new, which seemed good. Today though I went to install it, but before going through the whole procedure of taking off the steering wheel and lower dash panel I decided to test it by plugging it in to see if it would solve the problem.I removed the panel above the pedals and located the plug, plugged the new switch in, started the car, but to my dissapointment the same problem.

All the lights work, except the low and high beam. This leads me to believe that the switch I purchased it bad or there is some other issue. I emailed the seller to confirm that the switch does indeed work, but am wondering if I can test it myself? Visually the switch looks as if it's brand new, the mechanism also is very tight, not loost at all, which seems like a good sign, though I don't really know what the problem with these switches usually is, if its related to over use, a mechanical problem, or if the electrics just randomly go out.

As far as the problem being something else, could it be a relay, does this car, a 400E, even have a headlight relay? And does the headlight switch ever go out? What kind of electrical testing can I do I determine the cause? I really don't know where to start.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Please carefully check (remove and replace) the following fuses, F-2 - 16 amp. And all of the following 8 amp fuses f-8, f-13, f-14, f-15, and f-16.

hope this helps,
Acky

I've checked the fuses, and tested the low and high beam fuses to see if they're getting any power, and they're not. After looking at a wiring diagram it seems as if the issue has either got to be the headlight switch or the combi switch.

Most everyone with this same issue has had it be the combination switch, though it seems as if the switch gets progressively bad over time, mine just stopped working with no signs of it going bad previously. The switch I did by off ebay is used, but in excellent condition, and I would imagine that since the switch is a mechanical device that when it does go bad it will physically not work to well, both the one in my car and the one I purchased still physically work well, they're very tight and not loost at all.

It seems that buying a new combi switch is the way to go, though what I'm worried about is that after I buy this switch it still might not solve to problem. Then I'll know for sure that it's not the combi switch but something else which, I, or anyone else as of yet seems to know what it might be. I have a strong feeling its something else, maybe the headlight switch, but everything else (parking and fog lights) work. I'm trying to avoid spending a fair amount of money on parts that I can't return to not know for sure if it will solve the problem.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

reread post #2. Follow the circuit diagram (I'm unsure if the headlight switch feeds the multifunction switch or the reverse). Is there voltage at the start of the circuits (on both sides of the fuses)? Don't go by how they look but by what your meter says. The meter (in continuity setting) plus the circuit diagram will also allow you to electrically test the new switch you purchased without installing it.

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Hanno
'79 6.9 Sold (after 27 years)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon

Can you elaborate on that?

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

You description suggests the relay has failed.

In the rear section of your fuse panel there is a long relay MB# 126 542 01 32 (LAMP CONTROL).





Have a great day.

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1985 300SD
1983 300D
2003 Volvo V70

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I tested the new switch I purchased for continuity and it does work. I tested pins 1 and 2 with the switch in high beam position and pins 2 and 11 with the switch in flash position and when in those positions it did complete the circuit.

That's good new on that front, I'll test the original switch that's in the car to see if it's good also; it should be since the new switch didn't solve the problem and it works.

@whunter - It seems as if it might be the relay, but the fuses for the low and high beams aren't getting power. Since they're upstream of the relay shouldn't they still be getting power, or if the relay was dead even though downstream would that effect those fuses?

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

Try to find a good used relay, that is generally the issue.

Your problem may be as simple as the main (dash) headlight switch. I had the same problem recently -- no headlights, upper or lower. However, when I pulled back the combo switch (signal stalk) I still got high beams.

Like most folks, when I turn the headlights on, I turn the switch hard right. What I discovered is the headlight switch itself was worn (120 M miles) and (I guess) went beyond its limit, thus cutting power to the headlights. By backing off he headlight switch to the left just a tad, I get my headlights back on. Also on my car, the yellow "bad bulb" indicator on the dash lights up if I turn the headlight switch too far to the right.

I just bought a new headlight switch from Peach Parts and plan to install it this weekend.

Very true, though, I don't think that's the problem. My switch works perfectly for all other functions, and if I jiggle the switch (if that makes sense) it doesn't effect the headlights. I would imagine that since the headlight switch is mechanical it would slowly develop symptoms over time until eventually dead. In my case no issues with the headlights ever, then one morning they just don't turn on.

I followed whunter's advice and picked up a used relay off ebay that's been tested and has a warranty. We'll see by the end of next week if it's the issue, hopefully so

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500

My left headlight on my 300 ce will not come on most of the time. I have to get out of the car and gently tap it to get it to come on. I have used dielectric grease on connections. I think I may need to check the ground. All other lights function normally.

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