headlight adjustment

[gingergiant]

Hi, some of you might have read that i just bought a W208 '99, when i picked it up i heard a sort of hissing sound comming from right hand side, to start with i thought it was the speaker but after searching through loads of posts on loads of sites ive found out its probably got something to do with the headlight adjustment (vacuum). When you set the lights at level 3 the hissing noise goes away but the lights hardly move.

i had a look last night and the passanger side purple "hose" was disconnected, i reconnected this to the light but the hissing sound was still there and the lights hardly move through the adjustment levels AND now ive noticed my thermometer display in dash is now reading -35 to -40 have i done something , is this connected in some way to vacuum or have i moved something i shouldnt have.

I have removed the purple hose again back to the way it was but the thermometer still reads the same -35 to -40. any ideas what could be wrong.

thanks guys

Tosh

 

[andy27168]

Hi,
Temp. read out and vacuum headlight adjustment are not connected, i would say the temp display fault occuring is just coincidence, and will more than likely just be a new external temp sensor required it is fitted behind the lower small bumper grill on the passenger side.
Headlight levelling is simply a vacuum feed to each headlight from the PSE Pump (fitted in the boot) via the dash mounted regulater/switch.

 

[gingergiant]

Hi,
Temp. read out and vacuum headlight adjustment are not connected, i would say the temp display fault occuring is just coincidence, and will more than likely just be a new external temp sensor required it is fitted behind the lower small bumper grill on the passenger side.
Headlight levelling is simply a vacuum feed to each headlight from the PSE Pump (fitted in the boot) via the dash mounted regulater/switch.

thanks for the reply andy, sorry its taken so long to get back to you,

if it is the external temp sensor do you know a part number???

as for the headlight vacuum feed, i had a quick look in the boot, does this change from a purple hose to balck in the boot the reason im asking is there seems to be the same kind of hose thats in the headlights only in BLACK it just seems to be flapping about not connected to anything near the fuse box, is this it? if so i cant see where it would get connected.

cheers

tosh

 

[andy27168]

Hi,
The purple pipe goes from each headlight to a connector t piece somewhere on the passenger side, this t piece is then run into the cabin at the bulkhead adjacent to the ECU box, it comes into the cabin across to the drivers side to the regulater on the dash, out of the regulater into the cable way in the drivers footwell and on into the boot to the PSE pump, the pump is fitted in the boot behind the side trim next to the inside of the fuel filler cap, it is encased in foam.
I think you might be right about the colour change of the pipe, but i can,t remember for sure.
Regarding the pt. no. for the sensor, MB should be able to sort it out for you, it will most likely even be a stock item with your local dealer, when i bought mine it was less than a tenner, you might be able to clean up the connection as i have noticed both my cars the sensor pins get corroded.
This is what the sensor should look like.

 

[gingergiant]

thanks for he picture andy, temp gauge now working fine, the sensor had came away from the bumber, i removed it cleaned all contacts and fitted it back in bumber, now working a treat.

still no joy with the headlights though...

Tosh

 

[gingergiant]

just back from work, temp gauge now reading -38 ha ha looks like a new sensor is needed.

Tosh

 

[andy27168]

Hi,
I would be looking at the purple pipe under the bonnet and where it connects to the headlights, and at the regulater on the dash.
Once you have confirmed an air supply at the headlights, look at levelling units in the headlights as they may have come adrift from the headlight reflector.

 

[daveandfleur]

Hi. My headlights have stuck in the lowest setting, both sides (99 SLK 230K). Adjuster has stopped working. How does the system work? Is the default setting low with the vacuum sucking to 'up' or is it the other way around. Presumably one can check the headlamp side by pulling off the pipe behind the adjuster and sucking on it? Would this not then move the adjusters? Is there a fuse for the pump and does the pump operate anything else? The central locking is still functioning.

Is it a UK MOT failure if I disconnect and plug the lines then just set lights at correct level? Seems the easy option as with a 2 seat car with small boot and firm suspension it is a rather useless gadget.

Thanks for any advice

 

[andy27168]

Hi,
The PSE pump also supplies air to the A/C system, Orthopedic seats (if fitted), folding rear headrests (if fitted), central locking and i think it has something to do with the total closure and remote locking function, and on the SLK i believe it controls folding top functions.
On the SLK they suffered from damp and corrosion remove the pump from the car and thorougly dry out and clean the plug connectors, try this first before you do anything else.

 

[daveandfleur]

Thanks Andy
I'm a bit puzzled as the central locking works fine as does the folding top. Don't have any of the other gadgets other than aircon but that has other issues anyway.

I've just adjusted the lights up manually. Can't hear any hissing so assuming no vacuum leaks. As long as it's not an MOT issue and won't affect any other system it doesn't seem worth fixing. If I can find the pump I might take a look though!

Cheers
Dave

 

[jefrs]

The purple pipe and the temperature sensor wire both disappear into the mare's nest under the lamp. You have probably just pulled a sensor wire off, but it's likely to have more than one connector than the one on the bumper. Mine leads off from the sensor to some invisible control(?) unit up the back of the bumper.

I'd love to know how the automatic lamp levelling system is supposed to work in conjunction with self-levelling rear suspension. As far as I can tell, it does nothing at all. Is it supposed to stabilize the light beam so it does not flicker as you proceed over bumps?