Hi, I have a 2022 RF and my windscreen is constantly steaming up! Even if I clear it before leaving home it seems to steam up again a few minutes later - any suggestions as to how I can stop this happening would be appreciated, thanks.
Using Aircon?
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Yes, my first questions would be how do you use your heating and ventilation system and how frequently do you use the car.
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Hi Sue.
Make sure the air flow is set to fresh air and not re-circulation plus have the aircon running. Aircon isn’t just to cool air. Even set to warm the aircon will de-humidify the air.
HTH
Guy
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This always happens when my missus uses aircon then shuts the car off. When you come back to it there’s moisture on the inside of the screen which can freeze in winter. I advised her to turn the ac off a few miles before getting home to avoid it happening.
Another way it could happen is if there’s moisture present in the car, but a quick check and smell of the carpets and whatnot should rule that out.
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I realised in my daily driver last winter that the aircon was acting up. Well it hadn’t had a service ever, so overdue after 8 years.
It also doesn’t work below 3.5° so the manual says. All fixed now and working ok with just a check and regass.
Still steamed up a little if below 3.5° approx when in aircon mode, so I switch to give a blast of warm air, aircon off. My aircon usually stays on all year and I adjust the temp to suit.
I don’t know how the aircon or heating/ventilation is in the RF, my NC has had a regass too last year, it demists the car pretty well in auto climate control mode although it’s rarely used in close to freezing temps.
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I use de-humidifier bags over winter to take up the damp brought in by your wet feet etc.
Just leave one in the car until the indicator says it is full.
Then swap it for another and recharge the first one.
Takes around a week for a fresh one to need recharging.
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I have a 22 RF and find the front/side windows do tend to steam up in adverse weather if I have ventilation set on auto temp and auto distribution with aircon off. I found that switching distribution to screen and footwell setting worked better. In worst condition I resort to aircon too.
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You really should run the aircon the whole time as this circulates the oil that keeps all the seals lubricated. If you don’t the seals can dry out and you lose gas.
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You only need to cycle the air con occasionally to push the lubrication around. As long as it’s used from time to time the system should be fine.
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Try just setting the ventilation to auto with the AC on, except for the initial drive-off with the demist on. Assuming you aren’t getting any water in, you should gradually dry out the interior.
Check you have no leaks - make sure the carpet is not wet either in the footwells, behind the seats, or in the boot. If they’re wet, you can ignore most of what follows until it’s sorted out.
It’s the temperature drop that causes the condensation. Comfortable RH (relative humidity) is c. 50%. If for the sake of argument on a journey the humidity in the car settled to this level, at an in-car temperature of 22degC, then the air inside contains 9.7g of water per cubic metre.
Warm air can hold more water than colder air. The dew point for this concentration of water vapour is 11.1degC. At this temperature the RH becomes 100%. and if it gets any colder, it has no option but to condense somewhere, first on the coldest surface normally the windows.
Crudely, if you get out of the car and leave it like this, when the temperature goes below 11 degrees then water will condense unless the space is ventilated.
If your heater is on recirc. and AC off, the humidity in your car will be much higher to begin with - maybe 80 or 90%, unless you are using scuba gear.
One wheeze if it’s not actually raining is to to open the windows and let the car fill with cold air just before you park it. If you let in air at say 3 degC, even if the outside RH is 90%, the replacement air will only contain about 5.4g of H2O per cubic metre. That immediately reduces the dewpoint to 1.5 degC.
That’s all slightly theoretical in that the windows tend to be colder than most of the car interior, which only serves to make condensation more likely
You can work all this out easily with this RH calculator.
TBH, damp and even mildew is not uncommon in a convertible that’s parked outside over winter especially if used infrequently. A couple of damp-eater bags like these will help prevent it.
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When it’s not raining I’ll normally have the top down and never have any problems with the windscreen steaming up.
When it is raining, and I have to have the top up, then A/C plus fresh (not recirc) air, and again no problems.
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This site shows you the dew points.
https://meteologix.com/uk/observations/dewpoint.html
The driest air you will encounter will be on very cold winter’s days when you can see for miles. The air is so cold it can’t hold moisture. During the last cold snap the dew point was -3C where I live. It can get as low as -22C in Scandinavia.
Don’t equate cold with “damp”.
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Thanks everyone - plenty of things for me to try here. I am going to check the air circulation is set to fresh and order a couple of dry bags for starters!
Hi Sue,
If you or anyone else has tried to wipe the screen with their hands it will never stop misting up!
The trick is to clean the inside of the screen thoroughly with a good microfibres cloth and a quality glass cleaner making sure the glass is dry afterwards. After that never touch the screen again with your hands as the oil in your skin stops the screen from clearing.
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Thanks I will try that too 
Yes, I’d be checking the carpets for evidence of water ingress.
Check behind the seats as well as in the footwells.
Drains often get blocked by Autumn leaves which break down into a sludge.
It will steam up more than a bigger car because the same amount of driver breath is going into less air!
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