Sebo problem

I've got a Sebo X4 that's about 3 years old. It's been brilliant up till now, but it's now stopped automatically moving up & down.

Can anyone explain how the up & down mechanism works (ie how does it sense it needs to move), before I take it apart?

Thanks, Dave.

Have you checked the warranty first, they are quite long.

Cheers for the tip Dennis!

According to the Sebo website: SEBO offer a FREE 5 year parts and labour guarantee on all domestic machines...

But when I phoned them, this only applies to machines bought now; the guarantee on mine was only 2 years!

So, it still looks like I have to do it myself.

I assume it somehow detects pressure or resistance on the brush. But how?