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I've just bought a 2006 C55 AMG, and the Black/White LCD in the instrument cluster is barely readable in sunlight. Fine at night. I've removed the cluster and see there are multiple LED's illuminating the black screen at the back. They are all lit. My thought is that this LCD panel would probably be in a 'dim mode' when you turn the headlamps on, and in a brighter mode during the day, otherwise it would be just way too bright at night. If that's the case, mine is stuck in dim mode.
Can anyone confirm that their LCD display automatically dims when they turn on their headlamps?
Anyone else have a dim daytime display that they've fixed?
When I turn on my lights, the display illumination does not change.
It does dim when headlights go on. Did you go through your settings menu to make sure it was not set to that somehow? If it is working but just dim, I would think it has to be some type of setting for the display.
Good thought, but no luck there. I've been through the Operators and Command Operators manuals. There is a daytime/nightime/auto selection for the command/nav/radio display, but it has no effect on the cluster LCD. Nothing in the Control System options either.
At least I now know it is supposed to dim when the headlamps are turned on. Thanks.
Thanks, but I know about the instrument panel dimmer knob. That's not the problem. Knob turned up full, but lcd still barely readable in daytime.
scnad22
Before order/replacing of LCD display, please confirm first if it is the fault by doing the following:
Use "bright" light (concentrated LED works the best) pointed inside the white area of the Rev counter. Aim for the 7 red line and move light into the white area, following the red line direction (you will see a circular mark).
Do this during day-time condition and see if the display changes brightness.
Thanks Design4111, exactly the sort of instruction I'm looking for. I'm away from the car until Tuesday, but will try that test then and will let you know.
So it sounds like similar to my suspicions, there's a light sensor in the rev counter that controls the auto dimming of the LCD. (LCD brightness not controlled by turning headlamps on/off as I suggested) And and in my case, that sensor may have failed.
Amgen - I was aware that the brown C32 LCD's fade, and see threads on replacement and purchase, but wasn't sure if the same applied to the C55 black/white LCD's.
Just did the bright flashlight shining on the rev counter light sensor during daylight test, and Yes, the LCD display gets brighter - Hooray!. So, how do I fix the sensor? Red circle are the LEDs backlighting the LCD display. Blue circle is the light sensor controlling LED brightness. Close up of sensor. Back of circuit board. Sensor is other side of blue circle.
Last edited by sncad22; May 26, 2020 at 02:40 PM.
Reason: Add pictures.
Thanks for the update. My biggest clue was that you did not have any pixel problems nor intermittent behaviour.
However, just bear in mind that it can still be a bad solder joint or cracked PCB if the display did not respond.
You are right on the money with the second picture (blue circle). It is indeed a 6 pin LDR PCB surface unit.
Just be careful with the white dial pod's.
So you have two options now.
1. Buy a new cluster
2. Try to fix it.
Option 2 would be the cheapest of course, but, do you know a very good electronic repair shop (that deals with instrument clusters)?
Also, similar to the above sentence, it can still be a cracked PCB or bad joint.
Do you know any online places that sells electronic hardware (the one that you are looking for), or someone-else that is on the forum can chime in?
Last edited by Design4111; May 28, 2020 at 02:46 PM.
Fixed it with a work around!
From Design4111's suggestion to shine a bright flashlight at the light sensor in the rev counter got me thinking. The flashlight test worked, making the display come brighter in daylight.
So, I've installed a tiny led bulb over the sensor that I can turn on and off. Works like a charm!
Daytime - Turn led light on - LCD display glows brightly, readable in sunlight - Hooray!
Nighttime - Turn LED light off, LCD dims down to readable and nice nighttime intensity.
Here's what I did:
Purchased NE03-NWHP bulb, some wire and a switch for the dash.
Blacked out inside of instrument cluster compartment that stands over the light sensor, using small pieces of black electrical tape.
Soldered thin (24awg) wires onto the bulb.
Stuffed tiny amount of paper towel into instrument cluster compartment to hold led bulb. Tiny LED Bulb Bulb pushed into instrument cluster location that sits over the light sensor. Cut notches in both corners for wire to sit in, so the instrument cluster will still fit flush on the instrument circuit board. Taped the wires Installed switch connected to LED bulb, ground and power in the driver's side fuse box. Sunny with the LED turned off. LCD display hard to read, but perfect at night. Sunny with the LED switched on, causing the light sensor to turn up the brilliance of the display - LCD easy to read. Job done!
AWESOME! Way to DIY and find a work around. I might’ve chose an out of sight location for switch or just have the wire hidden but that’s being picky, what’s important is the ingenuity to work around the problem.
what made you try this rather than replace/repair the original component btw?
I did the work around for a couple of reasons.
I don't have any knowledge or skills with circuit boards, and don't know of anyone I could send it to to be fixed. I don't know if any of the components on the board are available to purchase, and don't really know what's causing the failure. The instrument cluster is tied to your VIN, so replacing the whole thing is not an option without somehow re-programming, which I assume would be $$$$.
So, for less than $10, I chose the route that I could do myself, and luckily its working, at least for now. Long term, I wonder if the panel will still start to dim if whatever component on the circuit board degrades further. Fingers crossed.
I know Design4111 is looking further into the route cause of the problem, so there may be a future fix, and I can remove my work around.....
Gotcha, that makes sense. I have pulled the cluster out of my ML a few times to solder/replace components and each time it’s a bit nerve wracking to plug it back in and see if everything works, even with prior computer board experience.
The c55 is a more complicated setup also so probably a good choice going with the fix you did until you know exactly how to replace the component in question.
Just a thought: try a 12VDC NC (normally closed) relay to power your LED that will open (and turn off the LED) when the green "headlights on" indicator comes on. Make it an automatic process. It will have to be a low current or solid state relay though. I would suspect the problem lies with the photocell (light sensor) getting weak, not the LCD.
I had this same problem in mine and never got that far.
The automatic dimmer in the rearview mirror was also experiencing a similar problem (but works in reverse, measuring a difference between front ambient and rear). Bright headlights behind me wouldn't make it dim, but putting my finger over the sensor in front of the mirror would. I was going to try tinting the front photocell slightly with a sharpie...
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