Condensation on outside of windscreen

1979-1991 280SE, 300SE, 300SEL, 380SE, 380SEL, 380SEC, 420SE, 420SEL, 420SEC, 500SE, 500SEL, 500SEC, 560SEL, 560SEC
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jas-300-sel
C Class
Posts: 47
Joined: Tue 25 Aug, 2015 11:12 pm
Model you own: w126

Condensation on outside of windscreen

Post by jas-300-sel » Fri 30 Mar, 2018 7:32 pm

Hi guys in the last couple of weeks I've been getting condensation on the outside of my windscreen in front of the two centre screen outlets.

The aircon is set to cool but not max
The ambient temp is around 28 deg and usually humid or damp/raining
If I adjust the temp wheel more into the white zone it's not as bad
I operate the climate control switch on the one with the clear up arrow and white down arrow
The compressor is leaking gas and the system doesn't work as effectively when it's over 29 degrees ambient and sometimes but not always the air con is slightly humid but only slightly.

The air con compressor will be replaced soon but this condensation is annoying me. Is it the vacuum pods or is it the air con? Is there a switch that isolates the windscreen vents? The auto climate control in the w126 is my least favourite thing in my car however in Australia it's all we got.

If it's the vacuum pods is replacing them all a long job or something my workshop could complete for a reasonable cost?

Thanks guys,

Jas.
'89 300 SEL

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Ivanerrol
Mercedes Demigod
Posts: 5769
Joined: Sat 12 May, 2007 3:21 pm
Model you own: w204
Location: Melbourne

Re: Condensation on outside of windscreen

Post by Ivanerrol » Sat 31 Mar, 2018 10:26 am

Just a symptom of cold air blowing against a hot surface.
I get this is most of my cars.
Windscreen wipers clear it.
Normally just goes away at speed.
W211 - E240
W204 - C280
W210 - E240
Departed
W202 - C200, C180, C180
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
W123 230
W116 450SEL
W140 420SEL
W210 E240
W209 CLK 240
W201 190e 2.6 (ex U.K.)

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91MercCoupeMBL
A Class
Posts: 12
Joined: Sat 06 May, 2017 11:02 pm
Model you own: w126
Location: Boston Metro West

Re: Condensation on outside of windscreen

Post by 91MercCoupeMBL » Sat 31 Mar, 2018 11:59 pm

Hi there Jas,

As offered above, when the windscreen temp gets below the dew point the moisture in the air condenses... especially in conditions you mention.. damp & humid..

I have experienced this condition since my first car with air con.. The car was new and it was a long time ago.. Before either of my Mercs were built.

I would guess the plastic foam seals on the air distribution flaps within the ACC box to be somewhat perished at this point.

In fact, over the last ten plus years or so, with both the 560 and an elderly 960 Volvo, I have found black & sticky foam residue bits on the floor at times..
Has come from the dash vents with the fan on high... Can't be sealing as effectively as new..

Cheers,

MBL

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jas-300-sel
C Class
Posts: 47
Joined: Tue 25 Aug, 2015 11:12 pm
Model you own: w126

Re: Condensation on outside of windscreen

Post by jas-300-sel » Sat 07 Apr, 2018 10:05 pm

Thanks guys
'89 300 SEL

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