Excessive condensation inside car - why?

[Peter C]

Post knee op I haven't used my W123 Merc for about a month. The car was parked on my drive and I started it up once a week to let it tick over for about 30 minutes at a time. The car has always been dry inside.

 

My knee is better now and last weekend I called upon the Merc to take my wife, little Charlie and me to London. Before we set off I noticed slight condensation on the inside of the rear screen. On route, with the heater switched on, the car was warm and dry and all windows promptly demisted. However, after we parked up and came back to the car a couple of hours later, there was a massive build up of condensation to all the windows, to the extent that I had to wipe the rear screen and side windows to see out. On route home, with the heater switched on, the windows dried out and stayed dry. I checked the interior for dampness when we got home, including lifting carpets and there is absolutely no evidence of any water ingress.

 

What causes the condensation and what can be done to reduce it?

 

Peter C

[M'coli]

Breathing - seriously! Breath less or have better ventilation and there will be less condensation.

[red5]

Air exit vents blocked? With the extra pressure from the blower its moving enough air to dry it out? No idea where they are on a Merc mind. Usually on C post or rear chassis somewhere.

 

Does vehicle have a cabin (pollen) filter? prone to causing misting when on last legs...other than that water ingress somewhere I guess. Sunroof ? Draining into sills/backing up ?

[Peter C]

Air exit vents blocked? With the extra pressure from the blower its moving enough air to dry it out? No idea where they are on a Merc mind. Usually on C post or rear chassis somewhere.

 

Does vehicle have a cabin (pollen) filter? prone to causing misting when on last legs...other than that water ingress somewhere I guess. Sunroof ? Draining into sills/backing up ?

 

All air vents are clear.

 

There is no polen filter.

 

Sunroof drainage is clear.

 

Car is dry inside.

 

I will ask my wife and boy to hold their breath next time they're in the car!

[scooters]

check the integrity of the door seals - our 850 has door seals that have slightly lost their stiffness which can cause water ingress in bad weather but not enough that you would notice.

 

check the integrity of the heater hoses - steam could be escaping from the cooling system into the dry air part of the heater system

 

an easy fix is to get onto ebay or halfords and buy a couple of silica gel trays - they are about 10 inches long by 3 by four and have silica gel crystals within - you just put them under the seats and they scrub the atmoshpere of moisture - work a trat and cost a couple ofo quid - this time of year we keep them in all vehicles

 

r

[autofive]

heater matrix leaking?

 

inside the boot getting wet and exhaust / heater heat forming steam?

 

or dodgy door seals

[Guest]

Seconded. Check the windscreen and door seals. The 480 has gubbed seals somewhere and I was getting ice inside the windscreen as well as outside. It also takes bleedin' ages to demist.

[Guest]

Seconded. Check the windscreen and door seals. The 480 has gubbed seals somewhere and I was getting ice inside the windscreen as well as outside. It also takes bleedin' ages to demist.

[Timewaster]

In my experience this can be caused by:

 

A. Blocked drains in the windscreen scuttle.

B. A feckin great rust hole in the floor

[red5]

Air exit vents blocked? With the extra pressure from the blower its moving enough air to dry it out? No idea where they are on a Merc mind. Usually on C post or rear chassis somewhere.

 

Does vehicle have a cabin (pollen) filter? prone to causing misting when on last legs...other than that water ingress somewhere I guess. Sunroof ? Draining into sills/backing up ?

 

All air vents are clear.

 

There is no polen filter.

 

Sunroof drainage is clear.

 

Car is dry inside.

 

I will ask my wife and boy to hold their breath next time they're in the car!

 

Good luck with that !

 

I take it you meant all vents, in and exit ? (sorry to harp on, but a lot of peeps have no idea they have body vents to circulate air)

[michael1703]

two of my cars do this, they are both well insulated and seem to 'sweat' the windows are running with water, theyre a 58 rover and 68 jag, my other shite doesnt do it as theyre all a bit draughtier

[Albert Ross]

Maybe a tramp has taken to sleeping on the back seat?

[lovejoy]

A "tramp" Steamer, perhaps.... ?

 

( I don't mean to infer your Merc is a bit of a barge, by the way )

[Guest Leonard Hatred]

You have a heavy breathing miniature sex pest living in your heater air intake.

[Pete-M]

Water is getting in somewhere, OR, someone has cleaned the windows with something inappropriate.

 

Had something similar happen with the Jag for a week or two after I had it valeted. Valeter doesn't do windows the 'right' way, he uses a load of Windolene (or similar) and a cloth to do 'em. This seems to mean the windows have a film or something which attracts gallons of water. I did the windows again, properly, and it hasn't happened since. Having said that, he did steam clean the floormats and they took a while to dry out completely.

 

With a W123 I'd be suspecting a boot full of water.

[Richard]

Isn't it from snow off people's feet?

[Mike D]

I'd be checking the boot as Pete M says, and the passenger rear footwell.... they're rekowned for having a leaky rear screen seal, mine was doing the same, from the pass side bottom corner....

[Tayne]

.

[warren t claim]

You could avoid the problem by using your E200 which shouldn't leak and has a toasty heater after 5 mins.

[Pete-M]

Valeter doesn't do windows the 'right' way, he uses a load of Windolene (or similar) and a cloth to do 'em. This seems to mean the windows have a film or something which attracts gallons of water. I did the windows again, properly, and it hasn't happened since.

 

What is the proper way?

 

The 'right' way to clean car windows (in my experience) is to never use a cloth, always use clean, dry paper towels. Spray the window with the cleany stuff (don't go mental with it, a light mist is more than enough), hold the paper towel so as to wipe the largest surface area possible (palm of hand, fingers outstretched as much as possible) and change the paper towel when it gets even slightly damp. Takes about 10 seconds to do each side window properly on the average car, and a minute to do the windscreen.

 

Almost any window cleaning stuff will do, but household stuff tends to attract more moisture than the industrial / car cleaning stuff I normally use (which is cheaper anyway). That Autoglym stuff that you wipe on / wipe off is pretty good but not ideal in this weather as it takes forever. Great in summer for shifting dead flies though.

 

Jesus H. Tapdancing Christ, I can't believe I'm sad enough as to post on the interweb how to clean car windows. I need to get out more.

[Peter C]

Gents,

 

I do use my E200 daily but when the weather permits I enjoy taking the W123 for a spin.

 

Pete-M, having just spent £450 having the rust around the rear screen fixed, I am pleased to report that the rear panel is 100% solid and does not leak. The boot is also totally dry.

 

The carpets are dry and there is no water in the footwells.

 

Door seals are good, no evidence of splitting or leaks.

 

The car has been parked up for a couple of days and all windows are clear. I suspect that the car misted up due to the driver's and passengers' excessive breathing.

 

Keep on truckin'!

 

Peter C

[worldofceri]

If the car isn't leaking and the condensation keeps returning then there must be moisture trapped in the cabin that won't shift. When you heat the interior up it will evaporate but when you park up and the cabin cools down it will simply condense again on the windows - unless you exchange the air inside for drier air from outside. I would suggest a long drive on a sunny day with the heater on and the windows open.

[Lacy]

At this time of year, the ambient humidity in the air is relatively high. When the vehicle is parked up unused for any length of time, the fabricy carpety foamy bits of the interior soak up this humidity like a sponge. When you then use the car and put your heater on this dampness in the fabric evaporates and condenses on the windows. It can take a good few days of regular use to dry the car out fully even if it already feels dry to the touch.