Headlites went out, is this a bulb issue...

It's possible the "main" lights elements have burnt out.
I believe it's a single bulb per side with both high and low beam elements inside.
Try replacing a bulb and see what that does.

Check the relay that powers the high beam, if memory serves me the relay is shared between those two circuits.You can swap the relay with a known good relay to prove if that is the issue.

You can not have High Beams on and FOG LIGHTS at the same time. The Body Control Module controls this. You may have a bad Body control Module

Headlights naturally become less bright over time. If the bulbs have not been replaced recently, I would start there. Look around the lamps for any damage, brittle wires/connectors, or signs of burning. If there is a wiring problem with headlights it is almost always right behind the bulbs.

sounds like the fog light is shorting out the system, and if its on the same side as the headlight, the filament in the bulb could h ave received damage also check the connections on each light, and also check the bulbs with a meter

there is a relay for them.are you sure is not bulb.

Did you check the socket that bulb plugs into.I hav seen where they melt for, the hat produced by the bulb.If that isnt the issue,I would suspect the headlight switch.But first stick to basics.Check all the fuses.

Most fog lights turn off when you put your brights on. Check their operation in normal mode first, if they turn off when you turn your brights on... this is normal.

To disable this you need the wiring diagram for your car, you will have to cut 1 wire to be able to have all your lights on at the same time.

how to install low beam light for 2007 mercedes e350

ck fuses. ck both bulbs. I know its crazy but I have had both bulbs low beam out. if the bulbs are good then the combination switch may be bad.