Just got my first Mercedes a 2005 280SLK and am confused over how the remote key works. My key fob seems to be infrared and only operates on the drivers door sensor, the handbook seems to imply that the key fob is a radio remote. So is it IR or is it radio and should it work when pointed at the passengers door? Did have a problem that the remote wouldn't open the doors, but this was solved by resetting the key fob. Thanks, John.
wongl
MB Enthusiast
It is RF but may optionally have an IR on the door handle (for the quick open/close option). It is also IR for starting the car.
wongl
MB Enthusiast
I am not sure if the IR on the door is only for convenience opening/closing of the windows/sunroof or it will unlock doors too? You will need to check with your owner's manual.
I would test this by trying to unlock/lock the car in very close proximity but without line of sight for the IR to the receivers in the door handle(s). It might just be poor range with your RF - something I have experienced previously on one of my cars.
I would test this by trying to unlock/lock the car in very close proximity but without line of sight for the IR to the receivers in the door handle(s). It might just be poor range with your RF - something I have experienced previously on one of my cars.
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What does the spare key do?
Is the car new to you or has this locking fault always been present or has this locking problem only just started?
You should be able to lock/unlock the car with RF from about 30 feet … or more… and you should be able to lock/unlock through walls and around corners without the remote having sight of the car. You have to be very close to the car door for the IR to work.
When you press each button on the remote, do you see a Blue/White IR light on the end of the remote when viewed through a digital camera screen as illustrated in video below?
Key fob IR test - YouTube
If you can pass the above camera test then the probability is that the key is ok and it’s the radio receiver that’s not picking up the signal from the remote. I don’t know where the receiver for the remote is located on your car.
Is this, here… http://homepage.eircom.net/~decdec/fobsound.wma ... the sound that you heard when you tested the remote through the radio?
Dec
You should be able to lock/unlock the car with RF from about 30 feet … or more… and you should be able to lock/unlock through walls and around corners without the remote having sight of the car. You have to be very close to the car door for the IR to work.
When you press each button on the remote, do you see a Blue/White IR light on the end of the remote when viewed through a digital camera screen as illustrated in video below?
Key fob IR test - YouTube
If you can pass the above camera test then the probability is that the key is ok and it’s the radio receiver that’s not picking up the signal from the remote. I don’t know where the receiver for the remote is located on your car.
Is this, here… http://homepage.eircom.net/~decdec/fobsound.wma ... the sound that you heard when you tested the remote through the radio?
Dec
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Thanks all for the response it was really helpful. I have established that the IR is 100% OK and the RF is non functioning. The key does send a code but for some reason it is not detected by the car, so could be a coding issue or RF receiver problem. I think I now need to get an expert to investigate the problem. Thanks again.
Did some more digging around and disconnected the battery for a few minutes. When reconnected the remote now works on RF and IR exactly as it should. Not sure if this is a temporary or permanent fix? Sounds a bit like a " switch it off and on again" type of repair, do hope software isn't Microsoft!
