There are 3 plates that will need to come off. The 1st of the plates is the outer black plate that you see when looking striaght at the headlight. It will have 3 screws you need to take out. the second plate is underneath the 1st plate. it holds the headlight in place. there are 4 screws, 2 at the top and 2 at the bottom; take all these out. Before you can remove this plate you must the the obsured 3rd plate out. This plate is tucked almost inside the the frame. take the 3 screws out and pull down and out, this may be difficult. the headlight can then be pulled out and unplugged then replaced by the new light. do the opposite order to put it all back.
If only the low-beam is out, you will need to replace the low-beam bulb. It is probably not necessary to replace the entire headlight assembly.
how to replace 2007 Mercedes GL450 Headlight Bulb Low Beam
A sealed beam headlight is just that. The unit is sealed and you replace the entire light. A composite is made of pieces that's why the name. To replace a composite you put a new blub in the back.
Carry it to dealer who will replace on low beam headlight for $15 +/- dollars in about 5 minutes.
The headlight has two filaments. One for the high beam and one for the low beam. The most likely reason the high beam is out is because the high beam filament is broken. Replace the bulb and it should fix it.
replace the high beam bulb
The Low Beam AND High Beam are in the same bulb. The procedure to change it will be in the owners manual.
replace passenger side low beam headlight
replace the low beam headlight bulb
Check the bulb Check to see if you are getting power to the socket
you will probably have to replace the headlight switch.
If you haven't already, replace the headlight. Chris