When you turn off a car with climate control do all the vent flaps automatically close. Reason I'm asking is my Civic seems to be misting up in the cold damp weather worse than every other car in my street and I've checked for water leaks and can't see anything.

In a normal car you would just slide the lever to shut off any vents but there does not seem to be any closed option on my control panel so I'm also wondering if the vents are staying open and allowing cold air and moisture in overnight.

Does anyone know the score with climate control?

have you had your filters changed in your AC?
They could well be damp if you use the AC a lot.

The filters are changed regularly, when I first got the car you got a metallic taste in your mouth when switching on the air con, took out the filters and they were black so I replaced them and ran an air con bomb through and that sorted it. I change them as soon as they look anywhere near grubby now regardless of mileage.

In the winter months I only use the air con for 5 mins every 4 weeks or so just to keep it working.

use the aircon all the time in the winter it will demist the car quickly as for climate control yes it will control all the flaps in the heater box..

(1) Check you haven't got the air recirculation flap closed --- should only be closed when the AC is on.
(2) Check the scuttle drains are clear
(3) Check the AC drains are clear.
(4) Check extraction vent in the boot is clear.
(5) Check for water under the carpets.
(6) Check for coolant loss.

What and where are the AC drains and the extraction vent in the boot?

As the AC evaporator dries the air by cooling and hence produces condensate from the humid air inside the car, the condensed water has to be drained away usually via a drain hose or hoses below the scuttle area.

If you are not using AC it is important that the heater system is set to draw fresh air and not on 100% re-circulation as humidity in the air with cause major condensation.

Most Japanese cars have one extraction vent at bumper behind side carpet lining of the boot/spare wheel well.

I'll check these out, thanks. The rear screen is prone to misting up easily but I've had everything out and it's always bone dry. I don't use the air con often and it's always set to fresh air which is why I wondered about the vents when I switch the ignition off.

If it's an 06 check under the drivers floor mat, something to do with the windscreen seal, but seems to pool under the mat.

Sure sounds/reads like your AC evaporator housing has it's Drains well and truly Blocked.

Clean them out ! Seriously.

Black on filter is Mold (or coal dust :-) .. a product of a swamp environment.. Lovely conditions you are breathing in there.!

Rear windows fogging used to be an issue with 88/89/ Civics.
Poor window & hatch sealing was the root cause surfacing when these aged out. Loong ago fixed.
Duuno about Hondas built in the UK though

I've got the 01-03 Coupe that was built in the U.S. You can't get any kind of workshop or Haynes manual for it so it's always hard to find info on it. Joined some Civic forums but TBH I'm not impressed with their knowledge, if you ask about anything mechanical they are lost but the threads asking about fitting big gay spoilers etc are full.