Uncontrollable bell jingle

[Kennedyforthe60s]

I have a 1961 Western Electric 500 that rings at random times.
Now I know this is a common occurrence but here's what makes it odd; it only has the issue at night, I have already tried to move the bias spring but the only other setting provided to much resistance, not allowing the bell to ring at all, and it always makes a dull clink about a second before it actually rings.
Any idea whats going on?

[LarryInMichigan]

It could be that your phone company is testing your line at a certain time during the night and the change in voltage is causing the ringer to "jingle".

Larry

[AE_Collector]

We have the same sort of testing here too. We call the system '4tel'. It automatically teststhe lines every day or two over the night hours. It is testing line insulation, resistance, voltage, etc. It definitely is known to jingle the bells in some phones but not a full ring.

Terry

[bingster]

I vote for poltergeists.