McLaren 720s windows fogging up - HELP

[JensenGT]

Hi PH'ers,

I have an issue I am sure someone knows the solution for, I have a 2020 McLaren 720s, recently and not in any specific cold or rainy weather but following collecting the car from a service I have noted the windows keep foggin up !, all of them, windscreen, sides and rear when driving with windows closed but aircon on, its driving me nuts as it never did this before, its like driving with it on recirc constantly, you know when it starts to fog glass, if I open a window it clears, the carpets / interior is bone dry, no moisture getting in but I am wondering if it is a HVAC issue or that my Circ button isnt switching from inside air to outside air, any tips ?

thanks all

[BunkMoreland]

Clean the windows on the inside!

[JensenGT]

really

[sherman]

I would go round every door seal with a damp cloth. There is probably something keeping it from sealing fully.
Add a large bag of silica crystals behind the seat or somewhere inconspicuious to keep it dry inside.

[JensenGT]

its not wet inside the car, its related to the aircon somehow, it clears if i opn window or dont use aircon

[RUNDLL]

Sounds like no refrigerant in AC system. The refrigerant obviously makes the air nice and cold in summer, but it also removes the moisture from the air when using the heat function.

I don't own a McLaren but have you tried taking the climate off of auto mode and manually setting the temp and making sure AC is switched on? Also, maybe try running it in it's coldest setting and make sure the air that comes out the vent is very cold. If the air is the same temperature as ambient, then you'll need a regas.

[ex-devonpaul]

Was the car cleaned as part of the service?

Set the ventilation system to intake rather than recirculate. If it still fogs up then it sounds likethere's water in the vent intake somewhere. Not sure about McL but I've had cars where detritus has blocked the scuttle drain resulting in water getting sucked into the pollen filter.

[AndM]

My car was low on gas for the aircon (no cold air in summer) and had been poor in the wet weather at clearing glass. Its getting serviced now so will see when I get it back if that helps.


I see you are alive to the recirc issue but I discovered that this was my biggest issue. VERY easy to activate the air recirculation button on the centre dash screen. Its the symbol on the bottom of the screen in the middle and very easy to hit by accident (touchscreens are awful for a driver to accurately hit). Mine had been activated (it is coloured orange when activated) and I hadn't even realised.

Turned it off and that made a good difference. Basically I had just been recirculating the same damp air.