Headlights

RONS TECHNICAL TIPS NO. 555 LUMENS. MERCEDES HEADLIGHTS.

EDIT 2023 - NON WORKING HEADLIGHT ADJUSTERS ARE NOT A UK MOT FAIL AS LONG AS THE HEADLIGHTS ARE A NORMAL HEIGHT. MOTORHOMES ARE EXEMPT FROM THE REQUIREMENT TO HAVE A WORKING ADJUSTMENT SYSTEM.

I've been meaning to get to grips with my headlights for a while. Not only are they pretty dim to begin with, after 20+ years they get even dimmer. I have seen several posts on here over the years about it. Bulb failures are quite rare, but if they happen, and you need to change a bulb, from the experiences of others it seems to be quite a job because you are working in a restricted space behind the front body work through the bonnet.

In principle, the job is easy - you twist off the cover, push and twist the holder, and it all pops out. The reality is quite different. The flipping things are stiff with age and because you are working blind you are scared of breaking them. What I discovered today should hopefully make the job a lot easier.

Basically, on a Merc Hymer, it's easier to tackle the job from the front! In the time it takes to mess about from the back, you can have the front grille off, 4 bolts, and another 2 screws to remove the indicator and surrounding trim, and then the whole headlight is exposed. On some vans I have been told that the surrounding trim has additional screws in teh aluminium side trim - look for these if your trim does not come away easily. Then 4 screws at each headlight corner and the whole light comes out. The glass lens comes off very easily with just one screw at each corner. There is a rubber seal between the glass and the body. You only need to take the glass front off if you intend to clean the silver reflector and the inside of the glass. If you only want to change the bulb, then leave the glass on.

Once you can get at the thing with both hands, the plastic dome cover comes off with a twist, and so does the bulb holder. Changing bulbs is then a doddle. I recently bought a set of higher power bulbs and a set of LED side light bulbs at the Hymerfest, and fitting them this way is easy.

I also had chance to examine and work out the headlight adjustment mechanisms. A lot of Merc vans have a headlamp height adjustment that is operated from a big knob on the dash, or a knob mounted under the drivers seat. The system is hydraulic - tubes full of water go from the knob to the back of the headlight. The system doesn't age well, and although I know a few owners who have a working system, the majority of us don't. Either pipes get damaged or they lose pressure, but basically they don't work anymore. Headlight height adjustment is less of an issue for motorhomes, as we generally have a constant ride height, so we just put up with it at a fixed height.

The hydraulic system is just about impossible to repair. If you are dead keen on height adjustable headlights then there is a firm in Germany who make a conversion kit to electrical adjustment. I have the link if anybody wants it.

So you have the wires going to the headlight for the 12v power, and a small plastic tube going to one corner of the back of the light. I just snipped it off. I then unplugged the wires to the bulb, and then had the whole unit in my hand.

The mechanism is quite simple once you get a good look at it. In one corner is a ball joint, in another corner is the adjustment arm from the hydrraulic tube, and in the other corner is the manual screw adjuster that you can see at the back of the headlight. The good news is that there is a manual adjuster screw collar on the hydraulic side, so having snipped off the tube, you can actually adjust the headlight to your desired setting. It's hard to put into words, but once you have it front of you it is easy to work out. 

However if you are happy with your general headlight adjustment and only want to change a bulb, or clean a lens, then doing it from the front is the way to go. 

The new 100w bulbs are really bright, but not ridiculously so compared with all these new technology bulbs on modern cars that are constantly blinding you, and the little blue LED sidelights are funky.

The whole headlight assembly is really easy to get at from the front. I cleaned and serviced and lubricated and polished the whole lot in about 90 minutes start to finish. Now better than new.