Just installed stairlift # 3 – we have several short flights 🙁 – and the brush on this one was jammed in its holder, looking much like the photo above.
I freed it up by removing the +ve lead and the terminal on the other side, and carefully pushing with a thin probe alongside the spring.
I could then see that the end of the brush had developed small shoulders – like a cold chisel does when it’s heavily used – and it had become jammed in place, with the spring not being strong enough to push it out.
Fortunately I was able to push the brush through its holder to the terminal side (used a small Allen key), gently file away the shoulders, and re-install it. The contact face was badly damaged, possibly because of arcing as a result of the brush (possibly) not having firm contact with the copper supply strip.
To the OP – or a moderator – maybe you could change the title of this tread to something more descriptive ….
