W211 E280 Estate Central Locking

[Jennifer Alex Seed]

I have a An E280 Estate 2006 and I am having issues with my central locking, all of a sudden it has stopped working and I need to use the emergency key.

I have tested the 7.5Amp Fuse 8 in the boot and that is fine. I cannot see any IR signals from either fob on my phone (which can normally see IR Signals) so I think both of those are not giving out an IR Signal unless I am doing something wrong, just press the keys as normal, right?

Recently I had an issue the the display in the speedo coming up red and displaying an image of a battery with the words "Visit Workshop", which I did and they replaced the small battery under the bonnet and that has gone away. However, shortly after coming back from the garage I noticed that if I put on the rear window demister the FM radio had poor reception. No idea if changing the batt and this is related, probably not. After a while that issues has gone away, but I am not sure if the RWH still works, how can I test?

Anyway, any ideas on why my central locking has stopped working and what I could do to try and narrow it down?

 

[gregcope]

Does the key work when very near the door and pointed at the IR reciever in the handle? Have you changed the keyfob batteries? Seems odd both might fail (assuming you have both).

If it does it most probably an issue with the antenna module in the rear. Your FM reception issues are likely related.

If it is this then …

In my old S211 one cable failed. Check continuity on the three cables. I ran one next to it and connected it in. Worked fine.

 

[Jennifer Alex Seed]

Does the key work when very near the door and pointed at the IR reciever in the handle? Have you changed the keyfob batteries? Seems odd both might fail (assuming you have both).

If it does it most probably an issue with the antenna module in the rear. Your FM reception issues are likely related.

If it is this then …

In my old S211 one cable failed. Check continuity on the three cables. I ran one next to it and connected it in. Worked fine.

I have changed the batteries in the fobs, I agree it seems odd but they are nearly 20 years old and could have gone wrong at any time. Pretty sure that the IR isn't working though as IR is picked up by my camera on other remotes just not the MB ones.

The FM reception returned to be fine, hence why I am wondering about the rear demister, I could do to check if that is working. Anyone any ideas how to do this with a Multimeter? Take out the relay and test the continuity? Not sure which leg holes to test though.

Where do the cables run from? The fuse box?