View Full Version : Non-working Infrared key

11-25-2011, 07:36 AM

One of the infrared keys to the Limited don't work, batteries changed, but no sign of life. So what can go wrong with these, is it a micro switch on the press point that may be worned? And is that micro switch replaceable?


11-25-2011, 09:20 AM
Could the key need to be re-synced to the car? I had to do this when I bought a new key (€150 if memory is correct).

The procedure, from the manual, is as follows:

For this purpose point transmitter to the receiver of the door or the boot and briefly press transmitter button. Turn the key in the ignition lock to position 2 within approx. 30 seconds. The infrared remote-control unit is again operational.

I would have followed this procedure with the new key and it worked for me.

Best of luck

11-29-2011, 12:22 PM
Arnt, have u tried re-synchronizing as suggested by Cavamman. This seems to be overlooked by a lot of 124 owners per other forums.


11-29-2011, 04:51 PM
Thanks for the suggestion guys, I'll try that tomorrow.

I've tried to split the key too, but I don't find any slot or typical place on it to insert a knife blade etc..


11-30-2011, 03:28 AM
It does split open, but I had to glue mine back together, the PCB mount micro-switch sometimes breaks a leg or develops a dry joint which is easily repaired with a soldering iron and a bit of patience.

Good Luck !

12-01-2011, 01:45 AM
It does split, that's good. I'll try a bit harder - it doesn't work anyway so it's already lost. I've been told that this microswitches do also fail on newer type keys.

I've tried the re-synchronizing without luck. Btw. turning the ignition to lock position #2 on my car, means ignition on. Is that correct, or is it the lock position just before ignition comes on?


12-10-2011, 07:04 AM
By the way, there is an easy way to test whether your key fob is outputting anything from the IR LED.... just use your mobile phone camera instead of your eyes - the camera will see what your eyes cannot.

I think #2 is ignition on, but not sure.

12-10-2011, 09:25 AM
Hi Arnt,

You can check the operation of the key fob easily - look at the emitter and press the button. There should be a red LED light up after a few seconds showing the 'key' is working.
I just had a similar problem with by 300D and tried a few things but ended up changing the tailgate receiver which was causing a problem.