Is there a mechanic in the house?

Steve Riley

Apr 26, 2003
Merc 190E
Hi guys and guyesses(?)
I'm hoping one of you is going to say "I had exactly the same problem and this is what fixed it.
Sorry if it's a bit on the long side.
SYMPTOMS....Neither alarm nor central locking/unlocking work via key fob.
BACKGROUND.... When I first bought this car, one press of the keyfob button and the doors locked and the alarm switched on after giving 3 flashes with the side lights. Unlocking was the same but only one flash.
Then, sometimes it would need to go through the alarm on/off cycle a few times before the little buttons went down to lock the doors, they would judder on each click but not go down, but unlocking worked first time, every time.
Went to lock the car a few days ago and nothing happened at all. No flash from the lights to indicate the alarm was set, no judder of the buttons, nothing. I changed the battery in the fob but still nothing although the fob light flashes when you press the button.
Using the key in the drivers door opens only that door whereas locking or unlocking the boot causes all the doors to lock/ unlock correctly. I've turned the alarm off under the bonnet for now but as you can guess I'm not happy doing that long term.
Any clues what to try first?
ps, in case you missed it, it's the alarm/ central locking bits both going at the same time that's puzzling me


MB Enthusiast
Jun 1, 2002
Berkshire & London
Porsche + BMW + Mercedes
I've heard that the vacuum pumps go on the central locking systems, and all I'm not sure if the pumps electrical or not....

If so maybe they have taken a live feed from that to supply the alarm.

Is there a fuse for the central locking???

Sorry, clutching at straws here......

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