How can you tell if the button is a front defroster or a rear defroster?

front looks like this \~/ and rear looks like this I~I

of course with more squiggly lines...but you get the idea!

Press the button. If air comes out the front defroster vents, it's the front defroster.

Usually a seperate button is the rear defroster. If its with the other buttons for venting and such, then its the front. Hope this helps.

With curved arrows for front defroster or just read this link for images & more info: http://en.wikipedia.org/wiki/Defogger

Either look it up in the car manual or go to the Merc site...or better yet...call the dealer. If you bought the car and they didn't give you the information, then they are poor dealers. (Honda/Acura..Toyota...Nissan, all tell their customers what all the buttons are for, when they buy the cars, info is also in the car manual)

the curved one

Jim H, do you know the 97 e420 well?

the front defroster is a setting on your air settings...the rear one is separate from that because it uses the wire to heat

the curved one the retangle is the rear

the curved one is for the windshield, the other is for the back