W203 Problem With Remote Locking Key

[Chrishazle]

One of my two keys is playing up, and I'm not sure why. It will not lock or unlock the car, but will start the engine. It's not the batteries, which was my first thought - so I changed them for new, checked the voltage of both old and new (both were fine!) abd still nothing. I also swapped the "battery holder" parts of the 2 keys over - the other key worked fine with either battery holder, but the faulty key will not lock or unlock the car with either battery holder!

Anyone got any ideas of how I can correct this problem?

Thanks!

 

[Diesel Benz]

Remove the circuit board from the key that does not work. You should find out something wrong. If not, take a good close-up photo and let others look at it.

You should find instructions on removing the circuit board from some old posts.

Could be an issue with the battery contact springs since your IR part is obviously working.

 

[Midland45]

I had a similar problem on my W209 and found it to be the contacts from the battery holder to the circuit board needed cleaning slightly and a slight bend to increase contact pressure. Also the battery contact required a slight clean. Maybe worth a check

 

[Chrishazle]

Seems the IR part of the faulty key is not working - no blue light visible with digital camera when buttons pressed, unlike the working one where I can see the blue light.

Have not been able to find an old thread on how to remove the circuit board - anyone know where it is?

Thanks for the help

Chris

 

[Diesel Benz]

Seems the IR part of the faulty key is not working - no blue light visible with digital camera when buttons pressed, unlike the working one where I can see the blue light.

Have not been able to find an old thread on how to remove the circuit board - anyone know where it is?

Thanks for the help

Chris

The car would not start if the IR part was faulty. The most likely reason for you not seeing the IR signal with a camera is that your battery is not providing power (like explained by Midland45 above). Note that the key gets power from the EIS when the key is in the ignition slot. This is why I "concluded" above that your IR part is working.

 

[Chrishazle]

Well, I managed to remove the circuit board, cleaned the battery contact areas very lightly with 600 emery then fluorosolv electrical contact cleaner, got the battery contacts as tight onto the batteries as I could, and also the bits of the contact strips that go onto the circuit board - and still it will not operate the locks. I know the battery part is OK 'cos I put it into the other key and everything works, so it must be something to do with the circuit board.

Any suggestions about what to do next (other than contact my local MB dealer and shudder at the cost!)

Thanks, Chris

 

[Diesel Benz]

At post #2 I suggested to take a photo and post it here.

If it has a problem with locking and unlocking it would unlikely be the switch parts (that tend to lose soldering contacts), also since you did not find IR signal, it still sounds like a power issue, perhaps on the circuit board itself. Did you find all solder points good?

 

[Chrishazle]

It went from bad to worse. When I started this morning I had one working key and one faulty. After messing around, swopping battery parts between cases etc - I now have 2 non functioning keys! I can at least use the car via emergency key as I can still start it with the main bit, having visitors here from Australia and needing the car (can't fit 4 adults and 1 child in my Porsche 968!!) really complicates things - but having spoken to MB Ashford it's a trip to the STAR machine as soon as I have available time (visitors off to London for the day without us, hopefully Thursday!). MB say it's unusual for both keys to fail, so problem could be on the car rather than either key hence STAR required. Credit card is already having a heart attack...

Thanks for the advice and assistance - will post again once I have the STAR results.

Re removing the circuit board - with the key turned so the board is at the bottom, there's a little white bar below it, the latch thing is to the left underneath the board, and the only way I found to free it was a very thin screwdriver through the notch in the centre of the white bar and a fine pair of tweezers to pull the board towards you - not easy, and the latch is quite fragile.

 

[Diesel Benz]

You should be glad you did not get more advice, you might have ended up more broken things with your car.

The 203 RF receiver at the car side seems to fail often and then both keys stop working. But the IR path through the door handle receiver should still work (did you try both keys by pointing to the door handle?).

You did mention the digital camera did not see the IR signal from the key? If that is the case, it cannot be fixed from the car (does not mean the car too could have something wrong). I find some confusing things here, luckily London should attract Australians long enough for the MB workshop to take care of the car.

 

[Chrishazle]

Dropped into MB Ashford this morning after dropping Aussies at station - workshop too busy to get car onto STAR - especially as "This type of problem on a W/S203 is not straightforward to trace and could take up to 2 days"!!!!

I cannot be without our 5 seater for the next 2 weeks so we'll struggle on for the moment - and try to figure out what's the best thing to do next. My warranty will cover repair if the problem is on the car, but not diagnostics - or keys if the probelm is on the keys. I don't fancy a bill from MB Ashford for 2 days fault tracing, so don't quite know what to do next.

 

[Diesel Benz]

I believe the most common issue with W203 remote is the RF receiver/antenna. Does your other key still emit IR signal? Did you try locking and unlocking the car by pointing with the key IR emitter directly to the IR receiver at the door handle (isn't the IR receiver at the door handle on a W203?)? If the key works and if the door IR receiver works, you can open and close doors remotely, but not very remotely, from a few feet.

In any case, if you do not get any IR signal from one or the other key, that key needs to be fixed or replaced. Once you know your keys are OK (one at least), you can start testing if it is the IR receiver at the car side or the RF receiver. This leaves a lot less diagnosis for the workshop.

 

[Chrishazle]

I believe the most common issue with W203 remote is the RF receiver/antenna. Does your other key still emit IR signal? Did you try locking and unlocking the car by pointing with the key IR emitter directly to the IR receiver at the door handle (isn't the IR receiver at the door handle on a W203?)? If the key works and if the door IR receiver works, you can open and close doors remotely, but not very remotely, from a few feet.

In any case, if you do not get any IR signal from one or the other key, that key needs to be fixed or replaced. Once you know your keys are OK (one at least), you can start testing if it is the IR receiver at the car side or the RF receiver. This leaves a lot less diagnosis for the workshop.

OK, the key that initially failed is not showing anything when I point it at the digital camera and press either button.

The other key - that was working but now does not - I can see a flashing light on the camera screen when I press the lock button and a single flash when I press unlock, so appears to be doing something.

When I take this key to the car and press the buttons - whether right next to the little black rectangle below the lock on the drivers door, around the front or rear screens or anywhere, I get no reaction from the car at all - no lock/unlock, no flashes from the indicators, no audible clicks.

It thus appears I have at least one totally dead key that I will try to get fixed over the next week or so.