Entry phone system door opening buzzer stuck on

[williamsmum]

The door opening buzzer for the entry phone system in our block of 6 flats is sounding constantly and leaving the door unlocked. I think it must be because the opening button on someone's in flat handset is stuck down, but everyone denies it is theirs. Could there be anything else causing this problem?

 

[OwainDIYer]

short circuit in the wiring, but a stuck button is the most likely.

Some systems use a relay to switch the lock, so the lock current isn't carried through the handset buttons, and that relay might have failed in the 'make' position.

Might also be the 'trades' button has been jammed or has got water ingress, if you have one.

 

[williamsmum]

I am getting residents to make another check of their handsets. We don't have a "trades" button so that can't be the problem. The system is quite old but we did have the panel with the bells and speaker replaced about 5 months ago. It looks as if it is watertight and, as there is a small canopy over the door, it should not get rained on. Does the system being old make it more or less likely that there might be a relay to switch the door lock? Any hints on tracing where the short might be if it is not in a handset? Am I right in thinking that, if we disable the lock mechanism (by disconnecting its cable) the phone part of the entry phone will still work but residents will have to come down to open the door manually to let visitors in? Unfortunately, the entryphone system does not have its own fuse but shares one with the hallway and exterior lights.

 

[sparkymarka]

Post picture of handset in flat