I was driving home tonight using both high and low beams on a country road. My orange warning went on and when I switched from high to low beam both low beam lights were out. My bumper fog lights worked as did my tail and brake lights. It seems odd that both front low beam bulbs would fail at the same time. Could it be a problem with my light switch?
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Headlight problem
- Thread starter Bill Walsh
- Start date
Check the N7 bulb out warning relay under the hood. If you have a spare, swap it in. Or, open yours up and check for cracked solder joints and resolder.
First question — is your car a 1992 or 1993 model, or a facelift 1994. Reason for asking is that they use different bulbs for the headlamps.
The first thing to do is ALWAYS to check the fuse of the headlamp circuit. Simplest things first.
If the fuse is removed and visually checked as being OK, then I would check power at the disconnected headlight plugs (rear of headlamps) with a multimeter, to see if power is flowing to the lamps.
If not, then you have a power interruption upstream. If you have power at the lamps, then you have either an internal lamp, or a bulb issue. I believe it to be the former, as it would be impeobable to have two main headlight bulb filaments go out at the same time.
Let us know what you find with the fuse situation (REMOVE it, don’t just look at it or rotate it in place) and with the power situation at the headlight plugs (both sides).
All power to the lights does go through the switch, and the turn signal stalk is also associated with the system. But let's get the basics first.
As far as I know, the bulb-out monitor relay in the rear relay portion of the fuse box is not a gating factor in the headlamp power circuit, and should not affect anything with regard to power going to the main headlight bulbs.
I will have to confirm the electrical pathway of the headlights via the electrical diagrams, but I do not believe that full headlight power flows through this relay, it only monitors system load to determine if a bulb is out.
The first thing to do is ALWAYS to check the fuse of the headlamp circuit. Simplest things first.
If the fuse is removed and visually checked as being OK, then I would check power at the disconnected headlight plugs (rear of headlamps) with a multimeter, to see if power is flowing to the lamps.
If not, then you have a power interruption upstream. If you have power at the lamps, then you have either an internal lamp, or a bulb issue. I believe it to be the former, as it would be impeobable to have two main headlight bulb filaments go out at the same time.
Let us know what you find with the fuse situation (REMOVE it, don’t just look at it or rotate it in place) and with the power situation at the headlight plugs (both sides).
All power to the lights does go through the switch, and the turn signal stalk is also associated with the system. But let's get the basics first.
As far as I know, the bulb-out monitor relay in the rear relay portion of the fuse box is not a gating factor in the headlamp power circuit, and should not affect anything with regard to power going to the main headlight bulbs.
I will have to confirm the electrical pathway of the headlights via the electrical diagrams, but I do not believe that full headlight power flows through this relay, it only monitors system load to determine if a bulb is out.
It has been a few years since I last played around with N7, so my memory is not the best. I believe power for the low and high beams does go into the N7 via various pins on x2 and out to the lamps themselves via x3. However if my memory is off, here are diagrams and mapping.
Attachments
Easy enough to pull the bulbs and check the low beam element with an ohm meter. I agree, it's unlikely that both bulbs failed simultaneously.
If N7 checks out ok (or, another N7 shows the same issue with good bulbs)... the next suspect would be the combination switch on the steering column. This can cause weird stuff when it fails.
If N7 checks out ok (or, another N7 shows the same issue with good bulbs)... the next suspect would be the combination switch on the steering column. This can cause weird stuff when it fails.
I had both headlights fail at the same time and it turned out to be a broken headlight switch--the rotary switch that turns them on and off. It sounded like a morocco when I removed the switch and shook it.
This happened while driving without touching the switch.
This happened while driving without touching the switch.
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Thanks for all your replies. My car is a 1994 E500. The fuses appear to be OK. My rotary headlight switch has already been replaced. In searching this Forum another member, Mike 52787, had a similar problem and it ended up being his combo switch. I'm going to let my shop deal with this and will report back when we figure out the problem.
I have had a combo switch go bad once before. Not a huge deal. Upstream of the lamps themselves, if no power, per my earlier post I would have suspected first the headlight switch and then the combo switch.
I think you found your culprit.
Thanks for searching the forum to find info. You are one of the rare ones here who take the time to tap into 15 years worth of good info.
I think you found your culprit.
Thanks for searching the forum to find info. You are one of the rare ones here who take the time to tap into 15 years worth of good info.
To close the loop on this thread I got my car back today from the shop and the problem was indeed the combo switch. Thanks for everyone's input.
+ 1 on that - particularly the ignition switch. Don't ask me how I know, but if your switch is still the original fitting, pre-emptive replacement will save you a HUGE amount of potential heartache somewhere further down the line!
How right you are! My saga included obtaining an emergency "get you home" ignition barrel from MB (at my expense), in order to drive the car to my local MB dealership to prove my ownership, which enabled me to purchase a new switch. Of course, no possibility of returning and obtaining a refund for the emergency unit i had purchased. It still sits on a shelf in my garage, if anyone's interested?
