Merciful

Hi MB folks, GLK350 2011 owner here.
Anybody faced such odd issue with LEDs on GLK: the driver side LED is lighting fine in low-beam, and the right one gives 5 blinks and then fades completely. I recorded the video here: https://streamable.com/eml8it.
I use these 3rd party LEDs: https://www.walmart.com/ip/TOPIK-Upg...k-2/6538003249
Do you have an idea what could be wrong if one LED is working fine and another one is not. Harness?
Answering probable question: the LED itself and decoder itself is working. I checked it connecting directly to battery, so the problem is coming only when connected to the H7 low-beam slot.

John CC

Did you try swapping the left with the right?

Merciful

Yes, I tried to swap it several times: the left LED does not work when inserted it into right slot. The stock halogen works fine in right position.
Any ideas?

habbyguy

Does it have a resistor (sometimes called lots of other things)? Without it, the car is going to "ping" the headlight with voltage, and come to the conclusion that the halogen bulb is burnt out (since the LED bulb draws so much less current). With a resistor installed, the LED headlight will look like a halogen bulb to the car, and it should work.

Merciful

Any hint how to check that? I'm not really electric-savvy

habbyguy

If the original headlight connector plugged directly onto the new LED headlight, there is no resistor.

If there's a large "lump" in the wiring between the vehicle's original headlight connector and the new LED bulb, there is a resistor "decoder" "adapter" or whatever else the resistor is called by the manufacturer.

Merciful

Ah, got you, it is my confusion in terms, I call it decoder, you call it resistor.
Yes, these LEDs have decoder attached, they do not work properly without decoders on GLK. That was my original assumption (about faulty decoder) and I already ordered a pair of new decoders from seller, but not luck. I tried to change the decoders and it didn't make any difference, same result.

habbyguy

If I'm reading your process correctly:

With either LED bulb and decoder / resistor in the right side, neither will light up properly. You swapped both bulbs and both decoders / resistors left to right, and both work in the left side, but no combo works in the right side.
With the original halogen bulb in the right side, it works fine.

I'd be kind of at a loss if that's all the case. The only thing I can think of would be that somehow there's a problem with the ground connection to the right side bulb connector, and that the halogen bulb is getting grounded via the headlight housing (I doubt it but that's all I can think of off-hand).

Bill F

The computer probably detects that the LED for some reason sees the left side out of spec and shuts it down.

MBKLUE

Did you try rotating the LED in the connector 180 degrees? In other words, if it's plugged in and not working pull it out, give it a half turn and plug it back in to see if it starts working.

MBKLUE

I don't think that would happen. It would almost be like allowing left and right headlights to be powered by the same fuse. It's simply not allowed for safety reasons.

MBKLUE

In this situation there is no such thing as a "decoder." A resistor is pretty much a given as LEDs do not operate on such a high voltage as put out by the battery/alternator. They also need current-limiting which a resistor will provide and a resistor can also be "spec'd" to provide the same electrical load as a normal incandescent bulb so no headlamp error code is generated. This is "magically" referred to as "error-free" LEDs. They simply add a resistor to help consume more electricity so the system is tricked into "thinking" a working, normal incandescent bulb is still connected. In reality this generates more heat and negates any power consumption savings over an incandescent bulb. In other words, your power saving LED that maybe only needs 25 watts to operate versus 60 or 65 watts for your normal incandescent bulb to work now has a resistor added to help consume more power and bring the power consumption back up to 60 or 65 watts. That prevents the system from thinking a headlight is burned out and from generating an error message. It's primitive stuff disguised as "error-free" high technology. Just P.R./advertising departments doing what they do...

calder-cay

What an awesome explanation !!

I never like to "enhance" my vehicles with technology which was never meant to have (nothing but headaches)
And this ^^^^ explanation confirms that.

Admittedly, we make it a point to NEVER drive out after dark, so no fancy LEDs required.

And even in the rare cases we DO have to venture out after sundown, the headlights are more than adequate !!
(we're out in the country)

habbyguy

Funny enough, I felt my original headlights were fine in the city (Phoenix, Arizona area), but where I didn't feel they were adequate was "out in the country". I do a lot of driving through rural and unincorporated areas, and I really (!) want to be able to see wildlife (deer and pigs primarily) as far away as possible. Texas back road speed limits run 70-75mph, and you really need to spot Bambi or Porky early to have a chance to slow down or otherwise avoid them. To that end, I installed a set of LED "bulbs" (another misnomer to add to the thread) and am very happy with them. And yes, they do have resistors, but I'm fine with that (though it would be nice if you could program "headlight bulb type").

And FWIW, I also run LED "marker lights" (the little ones protruding below the high beam) and "driving lights". Those make a big difference in lighting the way to the house / destination at night, and I much prefer the whiter (less yellow) light, though YMMV on that I suppose.

MBKLUE

I've never had the best night vision, even as a teen, so I was adamant that my next car (11 years ago) would have HID headlights and that's how I ordered my GLK. Had to wait for it to be built but it was worth it. The cornering lamps and all that are also very welcome. I'm not against LEDs in general but the bigger problem is retrofitting them in headlamps that have reflectors that are not designed for them. You might see quite well with them as the oncoming vehicle with the blinded driver crosses the center line and hits you head on :-(

Of course a lot of folks don't have the option of never having to drive at night.

LED retrofits for classic Italian or English cars can be great (but not headlight retrofits) because they generally came brand new with mediocre electrical systems that only get worse with time. The LEDs, of course, help take some of the load off the system - although they may not look period correct.

andreigbs

These kinds of threads remind me how great it is to have HIDs from the factory. Yes, the technology of HIDs has probably been eclipsed by LEDs, but the color output and spread of a properly aimed HID projector setup just can't be beat; at least not to my eyes.

I must say, of the few cars I've had which came with HIDs, the MB "Intelligent Light System" is hands down the best one. The auto high-beam function still amazes me, given that it's 10+ yrs old technology. The distance that you can see is phenomenal, and the sharp cutoff that does not blind oncoming traffic - and even adjusts the height and direction of the projectors' aim on the fly - is worth every dollar.

habbyguy

I am 100% in agreement that "headlight upgrades" have to be made with the thought of not messing up the headlight's ability to project the light properly. This became a sort of epidemic when all the boy racers "upgraded" their halogen headlights to HID. The halogen reflector housings count on the light all coming from one specific location (the filament) which is a very precise distance from the base of the bulb. Unfortunately, the HID bulb emits light all along a relatively long tube, so there's no way that the reflector housing is going to be able to focus it. The end result was a perception that "the headlights are brighter", but that was because everything around the front of the car was brilliantly illuminated, even if less light (than the halogen bulb) was actually being cast down the road where it actually does some good. The two real downsides to this scenario are the blinded oncoming drivers (as you mentioned), and the loss of night vision "down the road" by the glowing orb around the front of the car.

The LED headlights started out kind of rough, as it took a lot of emitters to bring the light output up to an acceptable level, making it difficult (impossible) to replicate the focus of the halogen light. Lately though, the single / dual emitter bulbs are usually designed with the emitter in the same position as the halogen filament, leading to no loss of focus. In fact, in my last couple LED conversions, the focus of the projectors improved. I'd say they're nearly on par with a set of HID projectors (though no car I've ever owned or driven equals the HID projectors in my 2003 BMW 330i ZHP, which lit up the country roads for a mile, it seemed).

Merciful

Can you please share the LED model you installed?

Silver Shadow

Use the link in the first post.

habbyguy

I'll go one better and show you how I put them in... ;-)

Merciful

OK, I saw your video before and even I already tried Cougar LEDs before, they didn't work. Same like all other LEDs I tried, in total I tried 6 or 7 LEDs. So looks like something is wrong with my specific GLK harness.

habbyguy

Very odd - hard to imagine what that could be. Generally, if it's got 12 volts, it's got 12 volts, but modern cars can be quirky, especially with the sensors (which are trying to help, but in this case making things difficult).

I guess it would be interesting to at least throw a meter on the lines powering the suspect headlight and see what the voltage is actually doing when the LED goes dark...

Merciful

Well, I haven't found the exact ones from your video, were little bit different. In fact, they are already non-existent on Amazon, those Cougars I tried were cool white, the below ones are xenon white, but they look very similar.

At those time 6 months ago I wasn't able to find those from your video, now I checked again and see them on Cougar official site. Do you think it worth trying these exact ones or it makes no difference?
I am not sure these F2Plus series on Cougar site are the ones you keep in your video, just look the same. Are they?

habbyguy

I certainly like mine, and I needed the removable base design for my right (non-OEM) headlight that uses a different style clip. But even so, the ability to rotate the "bulb" is a plus, and allows fine-tuning the light pattern.

Hope you do find the issue - I'm betting if you had a MB diagnostic (Star?) system you could figure out what the car THINKS is going on...

Merciful

So you confirm the ones from the second photos are the exact model that you installed?