Several of you have gotten your new MBs lately. As you become accustomed to the many great things about your car, I’m also sure you will start to notice some of its quirks. One of these is the “hazing” on the windshield. So, to be proactive to your inevitable questions, I’ve prepared the following treatise. Sorry for length.

The chemical solvents used to manufacture the plastic parts of your upholstery, carpets and interior dash components gradually evaporate over time into the cabin air. This curing process is natural, happens in all new cars to some extent, and is particularly noticeable in the summer months whenever the car sits locked-up in the hot sunlight. This outgassing is inevitable, and has to run it’s course. I once had a ’77 Honda Accord that hazed for three years, and the film was truly heavy and nasty to remove, especially from the hatchback glass.

The airborne solvents circulate through the climate control system and are expelled through the dash vents as you use the climate control system. Because they take the same path time and again, the aerosolized solvents are concentrated on surfaces directly in the path of the vents.

You will notice the “haze” on all of your windows, but the phenomenon is pronounced in the C-Class by the inclusion of the center-mounted, upper dash vent. Because the vent blows air over a very short distance directly at the windshield, the outgassing quickly concentrates on the windshield directly above the vent and fans out to all sides.

You can’t “cure” this problem yourself, but you can adopt one of two methods to control the “symptoms.” Some people advocate keeping the upper dash vent closed all the time. This strategy routes cabin air only through the more conventional vents in the dash and heating ducts below, distributing the haze throughout the car (including your face). Because the aerosol is more dispersed, it’s less noticeable. Eventually, you will have to wipe it from all windows and interior surfaces.

Realize, however, that solvents will continue to leach from the plastic surfaces within the closed-off portions of the system leading to the dash-top vent, patiently waiting their turn to get picked-up once the vent is re-opened.

The second strategy is to leave the dash-top vent open. In my view this is preferred, because it circulates air over all the interior plastic surfaces of the ventilation system, hopefully to accelerate the curing process. The only downside is that it encourages the hazing on the windshield, which you will need to clean weekly until the problem subsides. Thankfully, it’s not hard to clean at all. Use any regular glass cleaner.

I live in the Dallas, TX area, and we are famous for our two months of intense, dry summer heat (balanced by 10 months of truly moderate weather). The good news is that the heat seems to accelerate the curing process. I bought my car in early May, and kept the vent open throughout the summer months. I drove it to work 2-3 days each week, and parked it in the open sunlight. By October, the outgassing on my windshield was barely noticeable. My windshield now requires only normal cleaning.

Just chipping away at my "Junior" status, regards

Thanks Bob! That was very informative.

I've found that using Zaino glass polish on the inside of the windshield and windows makes subsequent cleanings with Windex much easier.

I always thought that was caused by my wife's chilli... :p

Hmmm....and here I thought that was just a biproduct of my most recent homebrew....Pumpkin Ale.

I'm amazed that this thread has been active for almost a day and no one mentioned Tommy and his chalupas (so I guess it will be me). On the topic of hazing, my 11-year old Acura is still outgassing (and it's been parked in the CA sun for 10 of those years).

Regards - the user formerly known as BT

Thanks for bringing up the Chalupas. I've been trying to give my buddy tommy some slack, so I'm proud to say I didn't bring it up.

Yeah, Hondas and Acuras and outgassing. Is that a pattern or what? With my '77 Accord, I found I had to use straight Vinegar to cut through the haze on those windows.

But I had to do it. Driving that itty-bitty car in 1977 among all those 70's AMPOS land barges, it was critical to be able to see out the windows for self-defense purposes...

Sort of like now, while driving my C320 among all the gass-guzzling, 4+ ton, no-brakes, behemoth AMPOS SUVs... Hmmm!

Funny thing is that I did go to Taco Bell for lunch, but managed to stay away from the chalupas, so no outgassing for me today.

I wonder what nice effects all these solvents have upon living things. I also would like to know if anyone's got information on the nature of the chemicals in the air inside a new car that's been closed up for a while.

I've actually found what works best and easiest is just wiping the inside of the windshield with a clean, dry all cotton T shirt!

Actually, it's not only solvents that produce this haze - dash board materials themselves - complex polymers - breathe all the time, especially under direct sunlight (UV and heat in particular). And MB, as many noticed, is not alone in this area - all cars are known to do that to some extent.

I see nobody has mentioned this, but there is a different reason the 203 has a fogging problem upon start-up. Under the dash-mounted center vent, there is a piece of felt-like material. It's black, and it's main purpose is to darken the opening so you can't see down into the vent. Which is to say, it's for cosmetic reasons. This material contains some kind of chemical, I don't know what, that makes the windshield fog. The way I've fixed it is to remove the dash vent, and replace the factory cloth piece with some felt of my own.

Here's how to take the vent out. First, I take a microfiche card and insert it between the vent and the dashboard. This protects the dash. Then, I have a thin, sharp plastic wedge that I insert between the card and the vent, and just pry up. Work your way around it, it pops right out. Be careful though, it's very easy to damage the dash.