Erick28 S350 Bluetec owner, newby....

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erick28

New Member
Joined
Jul 9, 2020
Messages
4
Location
scarborough
Car
S350 Bluetec
Hi Guys,
had a problem with condensation in driver side headlight. Having searched the internet for tips with little or no joy as to an easy fix I popped the bonnet and had a look at the structure of the headlight housing setup. I was drawn to the two black screw caps at the back of the headlight, which allows access to the bulb area. After a bit of head scratching I came to the conclusion that if both were removed this would allow some airflow into the sealed unit, ( hopefully ). Took the plunge and removed both, then left the car overnight and drove to work and back the next day, assuming warm air generated by engine running may help. Happy to say seems to have done the trick, headlight not showing any signs of water/condensation, black threaded covers replaced, hopefully problem solved.....
 
Did your trick work? I too have had some condensation in my headlight recently.
 
It comes back no matter what you do (unless you make permanent effective modifications).

Having a constant flow of air through it obviously would solve it for good like on the old Range Rover fog lights once they get warm.

However, MB highlight this can happen and is not a problem for the function of the headlights.

I found mine rarely occurred, if at all, when I used the car daily.

Now I see it now and again but never think about it now.
 
Good to hear erick28 you got it sorted.

John, I've changed my ballast 3 times over the past couple of years, now I want to create a permanent solution as I can't splash out for a new one or two.
And now due to the weather becoming colder I see it more often, plus I don't use my car that often so I probably won't dry the headlight out completely.
I've just checked my headlights out now and see the condensation. I know it will be clear in the morning - and I think we are having some warmer weather for the next couple of days.

During the last ballast fail I decided to change it myself as the it just blew straight away after I got home (drove back home in heavy down pour) - I'd hoped the place where I took it would have inspected the headlight but they did not.

Once I partially removed the bumper and extracted the headlight, I thought there was a scratch on one side but it was a 3 inch crack - this was not visible from the outside.
Bought a tube of JB Weld Plastic Weld - £7 and applied a few layers over the crack.
Applied polyurethane sealant (Puraflex 40) over the existing seal for extra sealing. And its all worked without any problems, its the other side that is showing more condensation that is the problem.

Good that I have pics for everything I did, just in case I had to do it again.

So, after scouring the forums I've listed what I have found -
1) Breather Vents
2) MB gel packs / desiccant silica gel / dust cover change
3) Fans/heater attached to the headlights - for some other make of car
4) Holes in the headlight unit
5) Maybe holes in the dust covers (wont be any use as dust covers then)
6) Gore patches


I think all I can do is look into what you have said John - having a constant air flow - I just don't want the ballast to blow again.
The connector that goes into the ballast becomes very corroded due to the ballast becoming full of water. However, I'm quiet sure that both units don't let water in.

I did wonder if it was possible to reposition the ballast from where it was currently located so that water would never collect around the ballast socket.
Last time I was able to remove the ballast connector from the headlight housing but the harness is tie wrapped internally.

I'll see how my mod works and keep track of it.
 
That sounds like a bigger problem than just condensation in the headlamps causing that.

I've yet to have a ballast die on my (touch wood). I have a 222 S500 by the way.

Do you believe it is the condensation killing the ballast?

Normally excess water is caused by blocked drain holes or missing guards / trim.

On the old Range Rover, it had a pipe at the bottom and a pipe at the top. The heat naturally wants to rise so it is exhausted through the top pipe. As it does that, it naturally brings in cool drier air (subject to ambient conditions!) to balance the air pressure in the fog light.
 
The headlight that had the ballast replaced must have blown due to the crack located on the underside of the casing and letting moisture enter. That crack was there when the garage replaced the ballast, I hoped they would have informed me. See images showing crack.

Whist I was applying my patch to the crack, I did try and locate the drain holes around the headlight unit but didn't know where they were located.

This headlight now works fine - with some condensation compared to the other side where the condensation is far greater. I'll take some pics when it occurs.
 

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