Hi everyone first post
I've just brought 2003 ML500 and wondering there is a button on the dash above the instruments panel can lift up by finger nail and shows <20> number on side and clues what it is. Also under front passenger seat plastic box with vents in it what is it

The button on the dash is the sun sensor. This is used to increase/decrease the climate control blower motor speed slightly, depending on the angle and direction of the suns' rays. The black box beneath the passenger seat is the TELE-AID control module.

Its a sun sensor MB service dept had to find out also. As to the box that is bolted to the floor underneath the passenger seat MB service didn't know either and I've been told it's a Sub Woofer. Thanks Cliff

I apologize for not checking your location before I replied to your question. I assumed your ML is a left-hand drive. In left-hand drive ML's the sub-woofer is beneath the drivers' seat. Sorry

I,d only just purchased the ML500 and was only advertised as four speaker instead of the 9 which it has and thanks to ILUVMILS and his reply I asked more questions and found out that the CD stacker had been taken out/pinched. The dealer is putting in a new one

Thanks Cliff