Another day another w215/w220 problem. The gauge cluster (literally) went on the fritz, first with blinking lights, then the smell of electrical smoke and the whole thing went dark.

After this happened the car could still be started (fortunately) and was rolled into the garage, but now it won't recognize the key, either with keyless, or with by putting the key in the ignition. Obviously I wouldn't know if there are any messages on the dashboard, it's fried.

Fortunately maturity and experience has kept me from becoming a psychiatric patient about the issue, but it' something that needs to be tackled. Is the gauge cluster linked with the key recognition or ignition module (or whatever Mercedes uses for this)? I have a remote memory of these cares somehow being able to start only a couple times with the gauge cluster removed before shutting down completely, to stop mileage fraud or something. I'm right now hoping this is the case, and that the gauge cluster will come back to life once repaired.

So now the obvious next thing: How the hell do I fix it? I won't be able to pull the gauge cluster to inspect it for another week or two, but I want to start looking at my options and possible solutions. I have a relatively complete electronics testing and repair lab, but that won't preclude me sending it off to be repaired if necessary.... assuming such a reputable service is available. Any advice?

If you don't have the two special tools required to remove the cluster, you need to order them now - they are cheap and readily-available.

Once you have the tools (keys), just run the steering wheel all the way out and all the way down. You can put a towel over the column to help prevent scratches. Insert the two keys into the small vertical slots on each end, pull the cluster out.

This will let you give it a close inspection to help decide that you want to do. Used clusters sell for $120 - $300 on eBay, and for $25 (yes, that is $25.00 US) at my local Pull-A-Part. There will be some complications if you change the cluster.

I have the tools. I've removed the gauge cluster on the w220 and replaced the screen that went dim with an overpriced used one on ebay.
My intention was to find the broken component and replace it. Good call on the junkyard. Maybe there's a specific memory module I can swap over to avoid complications.

If you enjoy tinkering and electronics cool but personally I would just use one of those w220 eBay cluster repair services for $160 and send in your original one so you don’t have errors relating to odometer

swapping another cluster is going to result in all dash marks on your odometer

Any particular one you might recommend?

Have you diagnosed the car with Star?

have you found what caused the short? It’s been raining and if the drainage in the engine bay by the driver side fuse box is obstructed, you will get that flickering if the water infiltrates the box. The drainage is under the fuse fuse box leading to the wheel well. Make sure you aren’t going to have other greater issues if this was a contributing factor. Sounds too fast to be a ic only issue. After finding the cause, it wasn’t just a random instrument cluster failure, then you can replace the modules. I can’t recommend but module rebuilders are listed around the net or eBay.

Did you check the fuses in the "hidden" fuse panel in the end of the dash?

Open the passenger door fully. Look at the end of the instrument panel that is now exposed. The sorta triangular piece snaps out to reveal fuses - one of which powers the instrument cluster.

good call since it was not listed as being checked. Everybody should always start with fuses.…..

Since the main problem was the flickering gauge cluster, I suggest to check the battery first. If there is a good source of power, better to check the ground connection or wiring.
Fuses and Ignition system can also affect your gauge cluster. If the gauge cluster itself is faulty, it could be interfering with the starting system.
The best way to fix the problem is to diagnose it first using a good car scanner. I recommend to use a reliable scanner called YOUCANIC scanner.
The codes will help a lot. Once the problem showed, you'll definitely know where to start.

I've now sent it off to be repaired. I didn't do a full diagnostic on it, but it was already giving me problems before and the screen was going dim.
**** now I broke one of my cardinal rules, but I'm fairly confident the thing **** the bed.

Shotgun approach.

Did you check the fuse? Did you check the front Sam? I had flickering the first time it rained in my new to me s55, which would be intermittently associated with rain. I researched all the issues with ic’s modules etc but it was fully due to that drain. In ten minutes the drain was cleaned and I’ve never had another issue or flicker, at all. Others have issue with the drain on the other side of the engine bay wiping out their cars. That’s a five minute job as well that can otherwise lead to tons of problems. Did you check those drains yet?

id make sure youve located the issue before plugging that module back in or it will likely have a short life. Batteries and grounding were mentioned and scanning for codes with a real scanner were mentioned. Making sure these are done will ensure you don’t waste any more money.

I got the gauge cluster back. I used the most well reviewed and expensive repair service, and I would not recommend them. One of the plastic tabs for the outside bezel is broken, by itself not egregious, but on the outside the plastic is broken and there is no easy fix for this.

Additionally they didn't address the dim display even though I asked them to.

That said the instrument cluster is back together and in the vehicle. The fuse for the instrument cluster (F79 I believe) was blown and I replaced it. The high voltage transformer for the instrument cluster was indeed blown and has been replaced. It appears to work. That said: the vehicle still doesn't start and only intermittently displays the mileage, leading me to believe there could be other issues cascading down the line.

I'm now looking into (finally) getting a good diagnostic computer for the car. I have a VM with the appropriate software, but I need the hardware interface. I am looking at this: https://www.vxdiagshop.com/wholesale...-hardware.html

Does anyone have suggestions for why the key might not be recognized/car won't start? Also why the mileage is only intermittently displayed?

More Details

I want to run down things specifically here:
1. The first thing I noticed was the instrument cluster would occasionally completely turn off, but it resumed
2. Right before total failure, I noticed the cruise control wasn't working correctly
3. After total failure of the instrument cluster, I could still start the car (I started it twice)
4. Once the car was in the garage and sitting, I got a total failure of the key. It would not turn. Keyless go didn't work. The door lock/unlock wouldn't work.
5. I sent the instrument cluster in and got it back repaired

• Fuse F84 was blown and replaced
• The mileage isn't displaying
• It did display once, but appeared to display incorrectly. It was only brief that it displayed
• I checked all other fuses and they appear ok: https://w220.wiki/Fuses#Cockpit_fuse_box_(F3)
• I will double check

[UPDATE]

I double checked, fuse F78 was blown, however replacing it caused a spark and the fuse immediately burned out.

Fuse F78 controls the following (per the benzworld wiki):

• Adjustable steering column;
• Anti-theft alarm system;
• Cruise control;
• Engine management unit;
• Ignition lock;
• Steering wheel heating;
• Steering column module;
• Windscreen wipers

Something in here is obviously causing a short. I will start checking.
The location of the anti-theft alarm system is the front left wheel well?
Where is the Engine Management unit?
the ignition lock refers to the key receptacle thing, right?

Found the culprit (it's what I suspected): the alarm siren was bad. Plugging it in and testing on the fuse point gave a 70 Ohm reading, which by itself shouldn't lead to a >7.5A current draw, but putting a fuse in brought everything back to life.

Can the alarm siren stay removed like this or will it cause trouble?

Yes it can stay removed

Of all places, reddit (the safe space for retards) helped me find the answer:

https://old.reddit.com/r/mercedes/co...off_cut_wires/

One addendum to post #12: I wrote the eBay repair service about my concerns, they immediately called and emphasized their desire (not just willingness) to make it right. They are sending a new bezel that I got back with some damage on the front, and should I have any concerns with the electronicns I may send it in and have it fixed immediately no problem.

eBay people refunded me the money after fixing the backlight transformer.

The car shut off going 70 or 80, and now when the needle passes that mark it hangs and goes wonky, even after resetting with DAS (that it will happily do with no problems, 0 to max to 0 again).
Reached out to german audio tech in California; after forcing a response, the answer was "I have no clue".

Which component on the boards is the high voltage transformer?

My cluster died, no dials or lights. Fuses are good. I got one from the junk yard in nice shape, and it works, but I can't program it because it has over 1000km recorded. Even with Vediamo and DAS I can't find a way to reset the odometer in order to let it pair with the other modules, so I'm thinking now about repairing the original.

Just google it; it's a very common fault. The transformer is for the backlight, so the little LCD should still work.

Then mine is a different failure, nothing works on it.

Aight shoot. In that case hit up a dedicated instrument cluster repair place.

Take one of the blown fuses and cur away enough plastic on the face to allow access to the metal tabs that plug into the fuse holder.
Get a relatively small working 12-volt light bulb, and three or four feet of "lamp cord" or "zip cord". This is two-conductor flexible electrical cable used to connect a table lamp to the electrical outlet. Solder one conductor to each exposed fuse tab, and to each bulb connection.

When you plug this test light into the Fuse 78 connector with the power on, the light bulb will glow. It will also allow sufficient power to flow to the affected circuits to allow you to do some testing, without allowing enough power thru to melt a wire. For example, if you have the glowing bulb where you can see it and you wiggle a wire harness and the bulb goes out, you have found your short circuit. If you disconnect the alarm unit, and the light goes out, you have found your problem.