Key fob issues

[markm730]

My keyfob is intermittently working and wandered how easy it is to change the battery in them.
When the car is left overnight or for a long period throughout the day the fob will work ok for opening the car , ignition and start up also fine. After use and when required to lock up it won’t operate and I’m left with the option of locking passenger door manually and using the actual key to lock drivers door. As I found out a few days ago this method doesn’t lock the boot!!
I’ve had a look at the fob and it doesn’t look like it comes apart in any way to get inside. Is there a way to replace battery without taking it to a garage.
Thanks in advance

 

[AMGeed]

Have a look on YouTube for one of the many videos showing how to change the battery. All the fobs come apart, just in different ways.
There are different types of key so look for one with your key shown for the correct info.

Get the correct batteries too CM2025 are the right ones. Duracell or Panasonic are a decent brand. Around £4 for 2

 

[steve333]

My keyfob is intermittently working and wandered how easy it is to change the battery in them.
When the car is left overnight or for a long period throughout the day the fob will work ok for opening the car , ignition and start up also fine. After use and when required to lock up it won’t operate and I’m left with the option of locking passenger door manually and using the actual key to lock drivers door. As I found out a few days ago this method doesn’t lock the boot!!
I’ve had a look at the fob and it doesn’t look like it comes apart in any way to get inside. Is there a way to replace battery without taking it to a garage.
Thanks in advance

Hi,does the spare key work ok?

 

[KillerHERTZ]

Check my video here:

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[pmcgsmurf]

Check my video here:

There is another version of the chrome key where the end comes out same as the black key (as I've just discovered).

 

[markm730]

Hi,does the spare key work ok?

unfortunately not, no. Same issue!!
Will check out the youtube vids.

 

[AMGeed]

If its not been used for a long time, the battery has probably died in the spare as well.

 

[KillerHERTZ]

As per my my video, hold down the button and point it at a digital camera to see if you can see the blue 'light'

 

[such01]

I had the same problem with both my keys and both batteries were changed. My original key would unlock but not lock.
I checked a thread on here and did the camera test on both keys, which showed the purple light via camera on all buttons.
The "dead key" did not show the little red light on unlock button presses.
The spare key only showed the red light when I pressed the unlock button for 2secs.
I deduced the original key was faulty and the second key was ok, but I just have to keep the unlock button pressed for a couple of seconds. It has worked fine since, but would probably need repairing at some point.
I sent off my original key to be repaired here:

Repair service for Mercedes A B C E S CLK CL SL Class remote key fob + New case 741414625990 | eBay

It works perfectly now, so I'm keeping that as the spare and will swap when my current key needs repairing.

 

[markm730]

Hi,does the spare key work ok?

The spare key is the same.
I’ve had a look at several videos via YouTube and it appears that there’s no infrared light flashing on the remote when looked at through a camera so I’m assuming now that there is no signal being sent to the car. As it stands at the moment the car is locked but my boot isn’t

 

[markm730]

Is there a fuse for the infrared signal, if so which one is it and whereabouts is it located?
Thanks

 

[markm730]

I’ve done this and it looks like there’s a faint flicker, at first I thought there was nothing but now appears that there is. Is there a fuse for the signal?