My wife has just taken dleivery of a used Mercedes A-Class Classic. It’s a nice little car but after a while we couldn’t open the central locking system using the key fob. We took the car back to the dealer and the fob started working again. The dealer took the car to a Mercedes specialist garage who diagnosed the problem as a faulty aerial unit which was replaced. All was good until after a few days it started failing again. On arriving at the garage it was all working normally again but the mechanic fixed a problem with the drivers door locak mechanism which wasn’t fitted properly allow the door to be opened using the handle even when locked.
Back home the car remote fob failed again. Well the mechanic had asked if we had any mobile phone aerials near us that could be causing RFI but we don’t. However, we tried turning off the Wifi which is located close to the vehicle (the car is parked on the front drive) – hurrah, we could unlock the car using the fob!
We have two Wifi installations in different parts of the house on channels 6 & 13 sharing the same SSID to allow complete signal coverage and have the units configured to allow seamless roaming. The unit nearest the front-door (and thus the car) was configured to use Channel 13, change it to Channel 1 and it all works without problem. In conclusion, the signal frequency of the remote key fob and must be very close to that of Wifi Channel 13 (which is allowed in the U.K.) which uses 2472 MHz and so the latter was blocking/masking the fob to car signal.