Aircon causing misty patches?

tsb

Car has recently (about 3 months ago) had a service and the air conditioning unit was regassed as it wasn't working.

Obviously with the nice weather the aircon has been used nearly every time the car is driven. Now there seems to be mist patches forming at the bottom of the windscreen after the aircon has been on about 20-30 minutes.

Anyone got any suggestions of what might be causing this?

Stooby2

It's condensation forming on the outside of the windscreen - the aircon is cooling the windscreen and condensation is forming on the outside at the bottom in the areas sheltered from wind by the bonnet edge.

OddballJamie

What Stooby2 said. Select the setting so it's pointing at you instead.

WestonDave

Most likely its spot cooling that point in the windscreen so far that its causing the outside of the window to be cold which in turn is condensing the humid air outside on the outer surface of the windscreen. Its effectively what happens on winter mornings - windscreen being glass cools so the moisture on the air condenses forming the misting you normally see all over the windscreen (and on really cold days it freezes as frosting!).

Sounds to me like its just a combination of the very warm humid air and your air con now being much more effective!

Strider590

Normal, nothing to worry about.

forgotmyname

If you have a pollen filter it maybe due for a change.

londonTiger

where on Eart are you based now to have condensation issues?

as fmn says, if the condensation is in the inside it may be due to the pollen filter. My car had serious condensation issues I explored changing all the seals and even changed the tail light seals (common failure after certain miles in my car).

Missed the obvious, the pollen filter was slightly warped from moisture over the years and had gaps in the seating and was allowing mositure through.

Also the air quality in the cabin was a lot better too. A rule of thumb, if you can smell the road smells, pollution, sewage etc while you're driving with the windows shut, the air filter needs looking into.

Changing filter changed that.

Strider590

Ok, pollen filter..... Possibly.

But it needs to be cleared up that the pollen filter doesn't stop moisture getting into the cabin. It's possible that the filter is wet due to blocked up drainage channels, BUT you'd have condensation issues with the AC off too.

Normally we turn the AC on to reduce condensation in the car, because the moisture condenses on the AC condenser (oddly enough) and drains off out of the car.

Patches on the windscreen are likely warm moist air hitting icy cold glass, you'll notice it gets worse for a few minutes if you turn the AC off but leave the blowers on.

I'm getting the same patches in my car (Vectra), because even though I know I shouldn't, i'm blowing the AC up the windscreen to help keep my onboard camera cool.

PaulJM

Mine does this when it's been serviced.
It's exactly what the first replies said - it's pointing at the windscreen and making those spots really cold on the inside, and it's really hot on the outside.

Change it to point at you, or at your feet, not the windscreen (I've read car manuals that say you should have it on this setting with aircon anyway, it's more efficient, apparently?)

tsb

Thanks for the replies. Put my mind at rest that its not a functionality issue with the aircon unit itself. It is probably directed at the windscreen so I'll alter that straight away.

Stooby2

It's not something to worry about even if it does happen. It's not a fault or defect, just one of those things. Some cars are worse for it than others.