Windows Misting Up

[Mike Edwards]

I've noticed on very cold mornings that the windows mist up quite badly.

Even with the de-mist setting or any other variation of the a/c and fan the problem remains long after the car is up to temperature.

Neither of my previous Vito cabs had any problems like this with their a/c so I was wondering if the a/c needed recharging or whether it suggested something more seriously wrong?

 

[Rory]

The a/c shouldn't work if it's less than about 3C - otherwise the evaporator will freeze.

I have to say that on various cars we have this seems a bit random though - some seem to work fine.

 

[Mike Edwards]

Shouldn't the de-humidifier element still work?

It's just bizarre as my vans always worked regardless of the temperature v

 

[Mike Edwards]

Had a good look round the car. There is a damp patch in the boot in the rear corner so perhaps the boot seal is letting water in.

Seems odd it is getting in to the air circulatory system. Checked the filter above the battery in the front and it is pretty dirty but doubtful it would stop fresh air getting in.

I did notice that the demist fan doesn't always blow through the slot across the base of the windscreen but does always manage to flow through the central vent on the upper dashboard.

I'm generally confused as to what the whole system should and shouldn't be doing. Only thing I am sure of is that it shouldn't be misting up to the point you can't see where you are going!

 

[gIzzE]

Have you checked the drains from the windscreen?

They come down beside the battery and often get blocked and this can cause issues.


Is the air con ice cold? Maybe it needs looking at?

 

[cobra7]

Was experiencing the same a few months back. Turned out to be the pollen filter was extremely damp - replaced with new which sorted the problem and no misty windows since.

A cheap fix but may just work.

 

[Silver Arrow86]

You need to get yourself double glazed windows.

My S Class never mists up

 

[Mike Edwards]

Was experiencing the same a few months back. Turned out to be the pollen filter was extremely damp - replaced with new which sorted the problem and no misty windows since.

Is the pollen filter the one above the battery under the bonnet?

 

[cobra7]

Mine is located under the glove box. (I drive a 1998 C43)

 

[Mike Edwards]

Have you checked the drains from the windscreen?

They come down beside the battery and often get blocked and this can cause issues.

Is the air con ice cold? Maybe it needs looking at?

In this weather it's a bit difficult to decide if the air con is working or if the ambient temperature is just freezing cold.

Will take a look at the vents tomorrow.

 

[Mike Edwards]

Removed all the trim around the boot edge and pulled the seal off. Loads of mould and other debris around the seal which might explain why the boot was getting wet.

Made worse by the nonsensical design of the rubber around the rear window directing water down on the the side trims around the boot. In theory going over them but, in practice, I think going underneath.

Bizarrely running a screw driver underneath the flexible rubber seal up the side of the rear window showed some decomposing rubbish underneath there also. I suspect this has built up over time and lifted the seal letting more water run underneath it down to the boot seal area.

Showing just how poor a design it is the only thing stopping water flowing straight in to the boot form this area is a small plastic connector that secures the trim around the seal to the metal underneath. Of course, drilling a hole through the metal in to the boot area so this small piece of plastic can be use to hold the two parts together is just plain dumb.

 

[Mike Edwards]

Having complained about the poor design of boot trim allowing water to run in I found out that Mercedes have completely changed the small plastic plugs used to join the trim to the bodywork. At least someone is paying attention to the small stuff.