XSeries-forum

How does the auto hold button work, is it the brakes being applied or handbrake or other?

It maintains the hydraulic pressure on the service brake rather than using the handbrake system.  It’s one reason why the brake lights stay on - the pressure switch is seeing system pressure.

All the time the lights are ‘green’ that is the service brake.  When red that means the handbrake is active..

used for stop start traffic where you don't want to keep foot on brake pedal. used to have a w211 e class, with that car you just needed to push down on the brake once and it would lock the brake until accelerator is engage.

I didn't know the brake lights stayed on. I haven't tended to use mine in certain circumstances such as on the end of a traffic queue to avoid someone piling into me. I shall use it more now.

Here's another related question. My cruise control has got brake assist and it's excellent. When it applies the brakes on a downward slope, do the brake lights come on?

Yes they come on sometimes worry about it un nerving the driver behind on a down hill stretch particularly if in eco
and the car is coasting

Yes that my thoughts as well. The driver behind must think he's following Mary Poppins )

I find it’s just as easy to gently ‘trail’ the brakes and the box changes down to 3rd or 4th to hold the speed using engine braking.  Touch the throttle again and it happily changes up again.

I tend to only use auto hold around town, reason being that the last thing I want after decelerating down a motorway slip road to a halt is the pads pressed against hot discs. It can lead to hot spots, deposits and warping.

Mike