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2012 e350 sedan. Right low bean head lamp out. I’ve replaced the bulb and checked the fuse under hood (in front of driver). No visible damage to module that holds the bulb. Any suggestions?
They are halogen headlights and the left low beam works. The high beam headlight works on both sides. Checked the fuse under the hood, in front of driver seat. Removed fuse. Looks good. I did not replace it. Thanks for your response.
I believe there's only 1 fuse for each headlight (29 & 30) so if the high-beam is working (on the side with non-working low beam) then the fuse it not the issue. The proper way to check fuse is not visual, but measuring voltage on both side of the fuse or checking the fuse for continuity. The low and high beam are controlled by the from SAM (N10/1) which happens to also hold those fuses. Here's what I would do:
First, is the bulb actually bad? May ways to tackle this and I'm not sure for skill set. You can power the bulb independent of vehicle with power supply, jump pack or battery (~12 VDC). More DIY friendly is swap the low-beam bulbs side to side. Did the problem follow the bulb or stay with same headlight?
If the left low-beam is out after swapping them, then the bulb is bad. Find replacement bulb.
If the right low-beam is still out after swapping them, then the issue is not the bulb
Now the question is whether there is power at the bulb connector inside the headlight housing.
Unplug the low-beam bulb and measure the voltage between the two pins on the connector. It should be ~12 VDC (or the same voltage when you measure the main battery.
You'd expect 0 VDC since the bulb didn't work (from the swap). However if you do have ~12 VDC, then there's a poor connection between the connector and bulb.
I suspect you might measure 0 VDC. The next check would be verifying for ground at the connector. If you have ground, then the problem is a lack of +12 VDC somewhere between the front SAM and the headlight. Then it gets complicated, either your scanning the vehicle, specially the front sam (N10/1) and/or verifying wiring between the front sam and headlight.
^^agree and also adding a comment about grounds.
On my 2011 E350 (halogen) I've long since gone with HID retrofit into the projector lens. Before and after the retrofit I had noticed an intermittent off on right bulb - sometimes it came on immediately sometimes it didn't, then came on a few minutes later.
Made me nuts trying to figure it out. I went the general diag route that bmwpower described above but as I was looking at both sides and checking wiring diagram I found that the ground for the right bulb ran through the left bulb connector. For some reason the ground wire out of the left bulb was crimped and almost broken. No idea how since its all inside the light assembly.
I mention this long story because if path to ground isn't there then there's no circuit. There are connectors at each light assembly (remove front part of plastic wheel wells to access). You can check to see if there is continuity to ground at the connector. You can also check for power and control at the connector to help locate the problem. Chances are that if one side works then the body control and lighting module is ok.
Not discounting checking for control or power voltage, but remember that proper ground is also needed. This includes removing and cleaning grounds bolted to frame. They may look good but it's the underside that can get corrosion.
^^agree and also adding a comment about grounds.
On my 2011 E350 (halogen) I've long since gone with HID retrofit into the projector lens. Before and after the retrofit I had noticed an intermittent off on right bulb - sometimes it came on immediately sometimes it didn't, then came on a few minutes later.
Made me nuts trying to figure it out. I went the general diag route that bmwpower described above but as I was looking at both sides and checking wiring diagram I found that the ground for the right bulb ran through the left bulb connector. For some reason the ground wire out of the left bulb was crimped and almost broken. No idea how since its all inside the light assembly.
I mention this long story because if path to ground isn't there then there's no circuit. There are connectors at each light assembly (remove front part of plastic wheel wells to access). You can check to see if there is continuity to ground at the connector. You can also check for power and control at the connector to help locate the problem. Chances are that if one side works then the body control and lighting module is ok.
Not discounting checking for control or power voltage, but remember that proper ground is also needed. This includes removing and cleaning grounds bolted to frame. They may look good but it's the underside that can get corrosion.
Just curious Mud,
I'm trying to envision this as I didn't look at the diagrams with that level of detail... I'd assume the connectors (low, high, parking, turn) inside the headlight would share a ground (daisy chain) and then a single wire would exit/enter the headlight assembly from a chassis ground point. Or are the headlights connected via a common ground wire and then to a single chassis ground point?
I guess it only matters if there's no ground at the connector in question and then figuring out where the problem is. Hmmm, interesting...
I'll try to look at the WIS diagram again, my initial thought was that each headlight assembly had a ground going to chassis. The factory connector to the left side low beam bulb (connector and wiring inside the housing) had a power feed and two grounds.
My assumption was that this was part of the individual headlight assembly ground wiring, connecting low, high, turn, and parking lamps. Then I noticed one of those two ground wires was damaged. I know that turn and park lights worked fine and I never did try the high beams. I never use them and basically didn't think to check them.
I had the car in the garage so it was easy to check low beams. I had cut that damaged wire in order to fix it. But before doing the repair I turned the low beams on and only the left side worked. When I touched the ends together the right side low beam came on. Tried it a few times and this repeated every time. Since repairing the wire the right side low beam has been perfect.
I want to look at the diagrams again to also see if the left side connector has 2 ground terminals, one for ground in and one for ground out to right side. And where the chassis grounds are.
BMWPower had asked about this and I also wanted to figure out the ground path.
I looked in WIS and found that my standard halogen lighting was pretty straightforward in terms of grounding. Left side ground was a daisy chain inside the assembly that connected low, high, park, and turn lighting. Right side ground did the same inside that assembly.
Left side ground at the connector goes to W9 ground location - it's on the outside of the frame rail just in front of the left wheel.
Right side ground at the connector goes to W2 ground connection - it's on top of the right side frame rail sort of in line with cylinders 2/4 generally.
Both are easy to see, there's several connectors terminating at that point.
So each light assembly has it's own dedicated ground. Bear in mind that my HID setup has a CANBUS connector, an ignitor, and a ballast, none of which require a separate ground wire. Does not use a relay harness. The CANBUS connector uses the stock halogen bulb connector to energize the ignitor to fire the ballast, all which work perfectly. But the system still relies on the stock ground circuit. I have since verified the ground contacts are clean and secure (removed/cleaned). It's been in the car for 5 years so it's not a new weird installation.
For the life of me I can't figure out why the right side light was doing what it was doing when I was messing with the ground wire at the left side light. The only thought I have is the perhaps the lighting module was cutting power (both left and right route through one relay) but it's a weak guess. At any rate, that's the grounding info and lighting is working fine. I'll quit while I'm ahead.
Been having the same problem on a 210 E550 #212 right light does not work after market unit lights are installed left side works fuses, light are good have to find were the wire power comes from have no power to the right side
I believe there's only 1 fuse for each headlight (29 & 30) so if the high-beam is working (on the side with non-working low beam) then the fuse it not the issue. The proper way to check fuse is not visual, but measuring voltage on both side of the fuse or checking the fuse for continuity. The low and high beam are controlled by the from SAM (N10/1) which happens to also hold those fuses. Here's what I would do:
First, is the bulb actually bad? May ways to tackle this and I'm not sure for skill set. You can power the bulb independent of vehicle with power supply, jump pack or battery (~12 VDC). More DIY friendly is swap the low-beam bulbs side to side. Did the problem follow the bulb or stay with same headlight?
If the left low-beam is out after swapping them, then the bulb is bad. Find replacement bulb.
If the right low-beam is still out after swapping them, then the issue is not the bulb
Now the question is whether there is power at the bulb connector inside the headlight housing.
Unplug the low-beam bulb and measure the voltage between the two pins on the connector. It should be ~12 VDC (or the same voltage when you measure the main battery.
You'd expect 0 VDC since the bulb didn't work (from the swap). However if you do have ~12 VDC, then there's a poor connection between the connector and bulb.
I suspect you might measure 0 VDC. The next check would be verifying for ground at the connector. If you have ground, then the problem is a lack of +12 VDC somewhere between the front SAM and the headlight. Then it gets complicated, either your scanning the vehicle, specially the front sam (N10/1) and/or verifying wiring between the front sam and headlight.
I have the same problem. Replaced I halogens H7 with some led and they were dim. After a week the right one stopped working and now when I plug a halogen H7 is very dim.and the voltage measured is 3.41v
anyone has any ideas ease? Thank you
I have the same problem. Replaced I halogens H7 with some led and they were dim. After a week the right one stopped working and now when I plug a halogen H7 is very dim.and the voltage measured is 3.41v
anyone has any ideas ease? Thank you
Where are you measuring? Loose terminals, bad connector, poor ground....
Where are you measuring? Loose terminals, bad connector, poor ground....
Hi . It's still me. Had to re-register.
i measure the socket that plugs on the bulb (the 2 terminals that connect to the bulb) and it shows 3.41v. Did not measure drivers side for its a bit hard to remove the cover.
Hi . It's still me. Had to re-register.
i measure the socket that plugs on the bulb (the 2 terminals that connect to the bulb) and it shows 3.41v. Did not measure drivers side for its a bit hard to remove the cover.
the bulb was installed when you did this measurement? its possible the car senses for current before fully powering the bulb, I've seen this on other CANbus centric vehicles.
the bulb was installed when you did this measurement? its possible the car senses for current before fully powering the bulb, I've seen this on other CANbus centric vehicles.
I measured without the bulb. The led buld doesnt work but when connected directly to battery it works so led bulb is ok. And strange enough the halogen works when plugged in. I have to test it night time to see if it has proper brightness or still dim. Now I believe it's a canbus problem for the leds were without resistor/decoder
I'll keep you posted.
I Now I believe it's a canbus problem for the leds were without resistor/decoder
.
Yes... very much likely.
Car thinks why load so low and take action.
There is no such thing as LED decoder in the true sense...AFAIK. So resistor you must use.
So where will the power savings be ? You end up heating up the resistor to match the H7 load, so that car computer wont go "mad".
Yes... very much likely.
Car thinks why load so low and take action.
There is no such thing as LED decoder in the true sense...AFAIK. So resistor you must use.
So where will the power savings be ? You end up heating up the resistor to match the H7 load, so that car computer wont go "mad".
yeah. :-/ and 55 or 60 watts in that resistor... ever seen how hot a 60 watt incandescent lamp gets ? it would need to be a 100W rated resistor, and mounted somewhere in the airflow as a 100W resistor is essentially a heater in a big heat sink.
ok, bad picture, the correct resistor would be a 2.5 ohm 100W (12V at 1.5 ohms is 4.8 amps, and 12V at 4.8 amps is 57 watts, which simulates the load of the halogen). a resistor like this should always be rated for about twice (or more) of the wattage actually drawn, so 57 watts would call for at least a 100W resistor.
I guess the LED which replaces the H7 would be like 30 watts or so ?
Our W212 with the multiled if I recall correctly its 15 watt low beam and 15 watts high beam, per side.
I dont follow the aftermarket trend for LED module replacement of halogen/xenon
an LED thats the same actual lumens is about 1/10th the power of halogen, or around 5-6 watts for a 55W Halogen. so if it was double the lumens it would be one fifth, so maybe 10 watts.
so maybe that resistor should be sized for a 30 watt load, 4.8 or 5 ohms.
Somebody mentioned this below, make sure your actually working on the low beam. I screwed around with mine for a week before I realized I was changing the wrong bulb
So to sum it all up, replace your bulbs with stock bulbs or bulbs meant for the car. When diagnosing with non stock parts following proper procedure goes out the window. OP stated this is due to improper choice in aftermarket parts (led bulb), necessitating a resistor to trick the oem system.
I recently upgraded to LEDs and mine did the same.
I wound up changing the plug adapter and wallah! It fixed it. So your wiring connection is probably loose.
Keep in mind that when the high beams are on, the low beams are off. Make sure that the High beams are turned off when checking your low beam connections.
In my '03 S500, I had to take the headlight out only to find my turn signal bulb melted the grounding plate mounted to the headlight bezel, maybe look at the socket and see if this happened? I may be way off base but after some solder on the grounding plate in the bulb socket, it worked fine. I was in a very long and slow funeral procession with my emergency flashers on for two hours.
On my 2012 like yours-- (mine is 4 matic) when hi beams are on the low beams are also on (booth are standard H7) bulbs).
Both passenger side bulbs are easily accessible. You said you replaced the bulb and it still didnt work.
Next is to put the working hi beam bulb in the low beam socket and see if it works,
New bulbs can be bad. Rare but has happened to me.Same with fuses.
You didnt say which fuse you checked; ie fuse 29 is for right side(passenger).
01-01-2021, 03:06 PM
