Remote central locking problem, R129

[Dave SL]

Sorry to bore you with more remote locking issues but none of the other threads describes the problem.

The car is a 1994 SL280 with a single button remote key fob.

80% of the time the car locks and unlocks with the remote key fob. However, the other 20% of the time it won't. If I try to unlock it with the remote the green light on the door handle or boot lock does not illuminate. If I then open the car with the key the alarm goes off.

If I lock the car with the key I can open it with either key or the remote so this is what I am currently doing.

The central locking itself works fine.

When I had the car serviced at a Merc dealership they didn't recognise the problem. When I asked why the remote didn't work from the passenger side they said that there's no sensor on the passenger door handle. However, the other week it did open from the passenger side (the green light in the handle illuminated). However trying to open the car with the remote from this side is the least likely to work. I presume there are sensors in each door handle?

The remote itself is OK. It's got new batteries and I've done the test with a digital camera to check the infra red signal.

Any ideas. The problem is so erratic. Why locking/unlocking from one side of the car should be any more or less reliable has got me baffled.

 

[stats007]

If you have an early car with visible sensor / status lights then you have sensors in both doors and the boot. I would suggest either the remote keyfob needs replacing - the alarm will only work if the fob is synchronised and this can fail with voltage problems - does the window close function work for both windows? If the keyfob is fine then module N54 may be at fault which you may be able to get repaired - you could at least check the connections as it's in the boot. The keyfob and N54 share a lock number so the keyfob would need to be reprogrammed.

 

[Dave SL]

The window autoclosure works. I tried it tonight.

As I speak the sensor in both doors are working but not the one in the boot lock. The failure of the one in the boot lock seems to have coincided with the passenger door lock sensor starting to work.

Where exactly is the control module. You say it's somewhere in the boot.

 

[stats007]

It should be next to the central locking pump on the right hand side.