viper

Has anybody had a problem with exterior windshield fogging in the the area above the center vent ? This only occurs with A/C on humid days. I know there is a grille replacement but I don't see how that could affect the exterior fogging that occurs. A quick wipe from the windshield wipers solves the problem but it looks pretty strange when you have this triangular fog appearing in the center of the windshield.

Chmeeee

I have observed this as well, I was test driving a coupe on Friday and it was doing that constantly, I meant to ask the dealer what was up with that but I forgot. I didnt actually notice if it was on the inside or outside though.

Patrick

rskinner

There is a tech bulletin regarding replacing the center grill - pn 203 830 1118 due to window fogging.

Oops, never mind, I see you state it is exterior fogging.

Fuzzo

isn't htis normal if you have the AC on and if it's hot outside.. why is this strange...

also what is the grille replacement for? what was the problem?

TIA

trench

I agree with Fuzzo, the center vent is different from most cars in that it blows cold air on the windshield - if you live where it's humid you'll get fogging as moisture condenses on the cold spot.

Cheers, BT

avlis

Solution: close the dash diffuser vent= no cold spot.

viper

There is a grille replacement for some reason as mentioned by rskinner. Does anybody know what this is for ? If the fogging was on the inside I could see why a grille change might work but the fogging is clearly on the outside. If the new grille is still perforated I don't see how this could change anything.

Lynn

The new grille is the reduce interior fogging due to outgassing of the plastics in the grille. I suppose the new grille uses different plastic.

Fuzzo

i didn't think the outgassing (sucha funny term) came from the grille itself.. i thought it was more from what was inside the dash...

rskinner

Do a search for "W203 C-Class tech bulletins" and the fogging issue was covered there by mbtech208.

viper

Actually the grille is made of perforated metal. No outgassing of plastics here.




Not really. It can only be assumed that the grille issue ONLY solves the problem if you have INTERIOR fogging. No mention is made of EXTERIOR fogging. The real question is does that new grille reduce exterior fogging also ? It could quite possibly deflect the air stream so that the window does not get cold. Unless MBtech208 answers this we will never know what the bulletin really addressed.

hokusbenz

i just leave the darn center vent closed. it is an easy solution.

mdp c230k

The center of the windshield fogs due to a residue released from the center vent, whether it is the vent or something else in it I dont know. The tech bullitin says to replace the vent to get rid of the problem. It is on my list of stuff for the first service visit.

Addy

I am 1 of the victim, when the a/c on for a long while about (20 mins) the exterior windshild fogging above the center vent, I just took my C240 back to dealer for this, they said it could be the vent not sitting in a proper position, it will take few days to fix it as they need to take out everything even dashboard. Also, you should check your the "vent control" knob as well, mind doesn't work, no matter what position, all vents are open.

revstriker

My car did this as well when I had it on "Auto". I switched over to manual and selected half-way between the floor and the dash on both sides. The fan is still on "Auto". No more fogging.

MB-BOB

Is this really a "problem?" I've driven several cars whose windshields condense moisture on the outside from the standard defrosting vents. All that's required is a good A/C defroster driven in a very humid climate.

viper

No its not really a problem. But I am sure we would all like to know why they issued a new part for this. Or was the new part with reference to some other problem. As I said before nobody really knows what the tech bulletin addresses - inside or outside fogging. MBTech208 where are you ? Can you print the specifics from the bulletin ?

MarkL

I've read this thread pretty quickly, but I think there is no problem. I have my center vent pretty much closed (upper dash vent), but I get some condensation above the normal defrost vents when it's very humid outside and the A/C is on. Some amount of air is directed to the defrost vents during normal operation, and it's just a law of physics that water will condense on a cold surface. I don't think this has anything to do with vent position, etc. It's simply the cold air blowing on the windshield. Just tap your wiper to mist for one cycle and it goes away. Like someone else suggested, try closing your center upper dash vent during these conditions to minimize the problem. Just my $.03!

MB-BOB

The tech bulletin concerns replacement of the grill assembly (the grill itself and the black mesh below) in the dashtop vent to minimize the fogging (actually chemical filming) on the INSIDE of the windshield from evaporating solvents in the vent plastic. Viper, the grill may have a metal core for support, but the outer surface on mine is plastic.

This was a temporary problem in my sedan, which I solved (pre-bulletin) by leaving the vent open through the Summer and letting the hot Texas Sun bake the solvents out of the plastic pieces... Clean the inner windshield when the "outgassing film" gets too objectionable, once weekly initially but every 2nd or third week toward the end of a 3-4 month period. BTW, the outgassing film also settles on the inner surface of your sunroof glass (if equipped), but is much less noticeable.

I had a similar problem in an early model Honda Accord that persisted the entire 7 years I owned that car, so this, by comparison is no biggie. And no, I haven't seen the actual service bulletin... just know there is one.

The OUTSIDE condensation issue is completely different, and I'm not aware of any service advisory for this common A/C problem, which can be addressed as Revstriker describes above... the catch-22 is that if you close the vent to stop occasional condensation on the outside, the solvents on the inside remain trapped below the dashtop vent.

Hopefully this clears up the confusion. Whew!

viper

Thanks MR-BOB.

On the coupe however the triangular perforated grille is all metal even though the underlying parts in the dash may be plastic. Maybe on the C240 and C320 the grille is plastic.

Lynn

Interesting, because my grille is not all metal.

trench

My Acura is 12 years old and it still fogs the windshield.

Of course, I imagine within a week after it stops the entire dashboard will crack like a crystal wine glass when Eliza hits a high-note.

Cheers, BT

MB-BOB

You know, Lynn, I think Viper is right. Tap on the dashtop vent grill... it sounds like metal to me afterall. Nice catch, Viper.

I do remember someone's summation of the hazing problem as coming from the mesh below the grille... Metal doesn't have a solvent leaching out of it.