very poor windscreen demist

[cbarrow]

Hi,

my 04 plate V40 (with climate control) is awful at demisting the windscreen. It even gets much worse (more fogged up) when set to demist before it gets any better - as if it is blowing moist air! Have replaced the pollen filter for a new one and it is no better.

Are there any drains in the heating system that might be blocked?

Is there a way of resetting the logic for the air distribution - just in case this is faulty?

Anybody found any good cures? It is awful for a relatively new car, especially when compared to my older S40 with old fashioned manual heater controls!

Many thanks in advance for any help the community can offer

[tt82]

the first thing to try is changing the cabin air filter, located above the passenger footwell.

[grass hopper]

make sure the aircons on,it should automatically come on when set to demist and is it working,one other problem could be a failed recirculate motor thats stuck on inside which will cause misting up.

[cbarrow]

Aircon's working (at least when outside temp is warm enough to allow it). Have changed pollen filter. Is the recirc motor easy to get to or buried in the bowels of the machine? (I bet it is the latter.....)

[grass hopper]

Hi,the motor is behind the glovebox.been a while since i have stuck my head under there,but if i remember right you should hear the motor run and see the linkage move to alter the flap.

one other thought,are the carpets dry ? no sign of water ingress ?

[cbarrow]

thanks for the info on the motor - will check it out. No sign of water coming into the car - so no joy there

[baldmosher]

Did you manage to resolve your problem in the end?

Seems like the same issue as mine, 52 plate, it's pretty terrible at demisting, although it does eventually it soon mists up again. Air con lights up when selecting winscreen only, and it does blow pretty cold after a couple of minutes, so I do think the air con is working, although at this time of year of course it's pretty hard to tell! No signs of water ingress anywhere so I don't suspect that's the issue.

It does demist the screen eventually, but it feels like there is hardly any airflow up the screen, there's some, but certainly less than any other car I've ever owned, although I can hear the motor blowing hard somewhere behind the dash, and the side vents certainly seem to blow OK. So I suspect either the flap for the windscreen isn't opening properly, or if it's a separate motor to send air to the windscreen, perhaps that motor is kaput.

I'll stick my head up behind the glovebox with a torch later, and see what's audible/in view as gh suggests. I'll also look at changing the filter if I find it up there. I did notice today that the interior recirc switch was stuck "off" but I assumed that was because the air con was switched on - the car seems to know best.

I still can't understand why mfrs don't put a heater matrix in the blower circuit for early frosty mornings. Or if they do, mine isn't working, hahaha!

[960kg]

.....on climate control units if the recirculation button is "on" for just the interior of the cabin it will never demist it has to be off.......i mention just in case the button may have been in the wrong position by mistake....i sometimes turn this on when in traffic because of the fumes and forget to turn it off....

[baldmosher]

On mine the recirculation button is only allowed to be turned on when the air con is turned off. (I checked this out on the way home tonight.) The car certainly seems to know what's best. :-)

The windscreen completely demisted long before I'd got home (it's only a 4 mile/15 minute commute), and it stayed demisted all the way home, despite me turning the fans down to half power once clear. I kept the heat on full the whole time (it was finally toasty warm by the time I'd got home - wonderful timing eh).

Funnily enough another guy in my block with a T reg S40 says his windscreen doesn't demist very well in cold weather either, so it's either a common problem, or a poor design, or we both have clogged air filters or something. I dunno. I will have a look under the dash and get back to this thread with an update once I've checked all the above suggestions!

[Volvon]

Mine seems to have gone quite poor also in the last week. I don't have air con though. But maybe I should change the pollen filter, I doubt its ever been done.