Need help! Why has key range reduced?

[m7m]

Suddenly, the key will only open (or lock) the door when placed close to the door handle. Changing the battery didn't help. Cleaning the sensor (the red glass bit on the door handle of E-class Merc, E200) may have helped.
Also, it now takes a few seconds after pressing the button on the key before the lights start to flash and the door to lock (or unlock).
Any ideas?

 

[renault12ts]

Welcome.

What year of car is it?

 

[Rory]

Sounds like the radio part has stopped working (either the key or car) and now it's relying on infra-red.

 

[m7m]

Further information

The year of the car is 1998.

To Rory:
Thank you for your replay. What do you mean by "the radio part stopped working"? Where is it located? Could it have beed affected by changing the key battery?

 

[Rory]

Not sure on a car of that age, but the newer ones work by both radio (so the work over a long range) and by infra-red, which is directional and needs to be pointed at the door handle.

I'm not sure what could be wrong, but if it might need resyncing to the car, although I doubt that if it didn't work before you changed the battery.

Presumeably you've only got the one key?

 

[m7m]

Further information 2

Rory
I relay appreciate your help.
I have 2 keys. When the door did not open, I changed the battery in one of them (bought if from Mercedes dealer who fitted it in the key for me).
At first, niether of the keys worked. Then, after cleaning the sensor on the door handle, they both started to work from a very close range.
What you suggest makes sense. It implies that I am now using the infra-red and was using the radio signal.
Any idea where is the radio signal detector located within the car?

 

[robpow]

I had exactly the same on a nearly new ML after not using it for three weeks and it had to go in for a reprogramming, apparently it had 'forgot' to accept the keys over radio and only worked over close range using the infrared eye near the driver's handle. The car's battery was fine and changing the battery in the remote also didn't make any difference.

Matt

 

[m7m]

robpow,
Interesting to hear from someone who experienced the same problem.
1. Was that the only electrical fault at the time? The reason I am asking is because I have just noticed that the passenger window has stopped working. (I rarely use the windows. So, it may have occured now, or months ago).
2. I assume you took the car to the dealer for reprogramming. Was it coslty?

 

[Bayram]

Suddenly, the key will only open (or lock) the door when placed close to the door handle. Changing the battery didn't help. Cleaning the sensor (the red glass bit on the door handle of E-class Merc, E200) may have helped.
Also, it now takes a few seconds after pressing the button on the key before the lights start to flash and the door to lock (or unlock).
Any ideas?

How long time did it take you to change the battery?
When changing battery you should be carefull not to reset the radio freq.

Think that you might need re-programming