Preconditioning fogs up the windows

[ZeroEmissionRequiem]

In humid weather, preconditioning tends to badly fog up the windows within minutes of operation. One time it was so bad water was actually trickling down on the interior glass surfaces. I've checked the cabin air filter, it seemed dry.

Understandably, preconditioning uses air recirculation (I've checked this with the glovebox removed) to make the process more efficient, but is the car really so stupid that it doesn't run the A/C compressor while warming up with recirculation? That's certainly a recipe for disaster...

[Deleted User 473]

Yeah, the integration between all the components is not very good.

the only way to activate the AC on preheat is for the setting to be on low temperature, and the cabin temperature to be over 18deg (low med high relating to 18 / 20 / 22 respectively).

If its just heating, it does not use AC.

Its annoying, as in my old petrol car, I have the AC on constantly for heating and cooling, it removes moisture and odours from the cabin. The 10th gen civic, with its 'auto' will only ever put the AC on when the temperature requires cooling. This means in the winter months there is not as much drying of the interior going on, and you are also not getting the preventative benefit of keeping the aircon system in use.

One thing I have noticed is that scuttle panel drain hole is very small. Mine is almost always clogged by even the slightest debris. This causes rain water and washer fluid to accumulate in the scuttle area, and this must add to the vapour that is drawn in by the blower. A quick poke of the drain hole by the wiper bolts, and it tends to be much better.

[ZeroEmissionRequiem]

I'm presuming pressing the A/C button until it constantly shows "A/C ON" means the compressor is running all the time? Even if that doesn't apply to preconditioning, at least it should maximize the dehumidifying while driving.

Good tip on the scuttle panel drain hole, I'll be sure to check mine.

[Deleted User 473]

yes, putting the AC on via the AC button will override the auto setting.

Modern cars are annoying, the AC will not fire unless cooling is needed, a hangover from the drive for more MPGs on petrol cars. Not to say that the same isn't true on EVs, but it would be nice to have the option remotely. On damp mornings in the UK the inside of the car will be a fair bit more fogged up than if you hadn't pre-heated at all...

[peniole]

What you're both describing is unusual. Ours dehumidifies rather quickly, which would require A/C. Even now in cold weather I can hear the A/C cycling on and off. Car is on auto with recycling on all the time. I've also had a 10th gen civic 1.5T petrol in saloon form in Germany, would also cycle its A/C on auto even in the cold. P.S. we and the e are in the UK.

[Deleted User 473]

What you're both describing is unusual. Ours dehumidifies rather quickly, which would require A/C. Even now in cold weather I can hear the A/C cycling on and off. Car is on auto with recycling on all the time. I've also had a 10th gen civic 1.5T petrol in saloon form in Germany, would also cycle its A/C on auto even in the cold. P.S. we and the e are in the UK.

Are you talking about the pre-heating though?

If you get in the car, the AC does seem to function. But with just using the fob or app to preheat, it does not (as far as I can tell/remember).

[Verone]

After hearing people mention this, now that the winter has set in here and I'm using the "warmer" preconditioning with the defrosting enabled, I keep expecting to go to the car and sit down in a lake.

I've had absolutely zero issue with the car fogging up, even when going outside to it having preconditioned itself in sub zero temperatures on a thirty minute cycle.

Are people maybe using a shorter 10 or 20 minute cycle and it's leaving the car messy inside? I can't figure it out.

[Deleted User 473]

A lot of it has to do with the surrounding area and weather.

There are times when preheating works fine, and there are times when the outside is very damp and even a 30 min blast at high temp won't do anything to clear the moisture.

0 degrees is not a problem , there is no moisture in the air at this temperature. The air is crisp and fresh, so the car preheats fine.

Its the 6am to 7am window, when its barely sunrise, and its rained all night, its maybe 5 to 10 degrees c and there is a slight fog and moisture you can feel in the air on your bare skin. That's when it tends to fog up, because the car is just sucking in moisture from the air, and heating it and pumping it into the car without the AC to dry the air out... That's a typical UK morning outside of a city location. Lots of trees and grass and nearby waterways all give off moisture. You drive out of your housing estate, and the country roads are blanketed in visibility reducing fog. This is when you need AC with the preheat.

Once you get in the car, and the AC is running, the moisture is slowly removed.

[peniole]

Maybe it's because I leave the car on recycle before shutdown, so on occasion when I do use preconditioning it doesn't fog up because it doesn't pull outside humid air in. Try that perhaps?

[ZeroEmissionRequiem]

Outside, rainy day, 10 minutes after preconditioning started:

After about an hour of driving with climate control running with A/C forced ON, I parked in the garage at home, then ran climate control on max heat with A/C still forced on for about 10-15 minutes. I returned to the car about half an hour later, activated preconditioning, and this is how it looked after 7 minutes:

I also took a video of the process; the side windows start noticeably fogging up about 2 minutes in, and it's as bad as it gets after 6-7 minutes, at which point the vents on the A-pillars start clearing out small areas on the side windows. Since the garage air is quite dry, this humidity has to be coming from somewhere in the car...but I've made sure the carpets under the rubber mats are dry, and I keep one of those "dehumidifier pillows" in the car too. I've just re-checked the cabin air filter, it indeed appears dry, but I took it inside now just to make absolutely sure it's dry by morning...

Maybe it's because I leave the car on recycle before shutdown, so on occasion when I do use preconditioning it doesn't fog up because it doesn't pull outside humid air in. Try that perhaps? :?:

As I wrote, at least on my car preconditioning activates recirculation regardless of whatever its state was before shutting down. I checked this by literally looking at the inlet; once preconditioning starts the lid is up and it's taking in cabin air.

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