The indicator for the extension being in use on my bellset 44 has a problem in that it is not clearing after it has been set. There is nothing mechanically preventing it from returning, as moving it to the "set" position by hand allows it to return without problem. It seems more that the solenoid is remaining magnetised until its armature is manually released.
I do notice that a switch (marked "I1"?) on the
diagram places a 2μF capacitor across the coil, but I'm struggling to identify what that switch is.
Any thoughts on the cause of the problem?