central locking sl 300 1991

Hi,
My remote central locking works randomly. In particular the remote will open all doors, but only when it feels like it. The lights on the door sensors don't usually work even close up but sometimes do.With the key inserted it will only lock the door you're using the key on, the boot, internal boxes, and filler cap. It never locks the opposite door. Two merc dealers have plugged it into their "computers" and identified NO PROBLEMS. After this they seem flummaxed. Is there anyone who can suggest a check list we can run through ourselves? I don't want to re-invent the wheel if this is a common problem, or have a merc garage spend hours testing every single component.

thanks,
Sarah.

sounds like an air leak in the system.

Many thanks Sleepwalker.

SJP