2020 Si HVAC - Windows Fogging Up

aaaaah

Member
I have had my Si since the very end of December and the one big thing that I notice is that when it's wet outside (rain/snow) the longer I'm driving, the worse the windows fog up all around the car. It starts with the rear door windows and then creeps up to the front windows.

Normally I just leave the HVAC in auto and let it deal with it, but I've never had a car with climate control that seems to be unable to stop the windows from fogging up, especially as it gets worse the longer you drive it.

Any ideas?
 

DoctorC

Senior Member
I have had my Si since the very end of December and the one big thing that I notice is that when it's wet outside (rain/snow) the longer I'm driving, the worse the windows fog up all around the car. It starts with the rear door windows and then creeps up to the front windows.

Normally I just leave the HVAC in auto and let it deal with it, but I've never had a car with climate control that seems to be unable to stop the windows from fogging up, especially as it gets worse the longer you drive it.

Any ideas?
Do you have the system recirculating or is it pulling air in from outside?
 

shoegazer

assistant to the assistant manager
I have and have heard others mention the same issue. Our cars, for whatever reason, seem to do this more than previous Hondas.

More than one person has had to adjust to how this newer AC system works versus the older designs. It seems like running the AC is necessary more often than in previous designs.

Maybe try the 'defrost' mode and adjust from there.
 

ebbtide

Member
Outside air.
Have you tried to select recirculate to see if it at least helps? That's the setting I keep my AC on religiously mainly to avoid fumes from other cars coming in the cabin but I imagine itll help the car maintain an equilibrium inside since it's not having to contend with the moist air being brought in. Just a theory I'm no physicist.
 

aaaaah

Member
I have and have heard others mention the same issue. Our cars, for whatever reason, seem to do this more than previous Hondas.

More than one person has had to adjust to how this newer AC system works versus the older designs. It seems like running the AC is necessary more often than in previous designs.

Maybe try the 'defrost' mode and adjust from there.
Towards the end I turned off auto and forced it in to ac on, feet/defrost which started to clear it a bit. When it's in auto, the climate screen had it at feet only and ac off. If this works, I'll just have to ignore auto and keep it manually set.

I had to get rid of my 235i to save money for a big move, and I never had to to touch the HVAC beyond the standard defrost/temperature. That and having the settings always visible helped me know what was going on.
 

aaaaah

Member
Have you tried to select recirculate to see if it at least helps? That's the setting I keep my AC on religiously mainly to avoid fumes from other cars coming in the cabin but I imagine itll help the car maintain an equilibrium inside since it's not having to contend with the moist air being brought in. Just a theory I'm no physicist.
I've tested that with no real change. The real key i think is that it isn't running the ac compressor which would dehumidify the air. I'm assuming it deems it unnecessary as it is heating the air for me (25F outside today)
 

aaaaah

Member
As a final word to this, it was definitely due to climate control not running the AC compressor when heating the car which was causing the fog. Running the system in manual with the AC on results in clear glass.
 

shoegazer

assistant to the assistant manager
One other odd quirk about this:

Since some of our AC compressors seem to fail due to dried seals from lack of use over the Winter; using it as a general rule may help it to last longer.
 

DoctorC

Senior Member
One other odd quirk about this:

Since some of our AC compressors seem to fail due to dried seals from lack of use over the Winter; using it as a general rule may help it to last longer.
Tbh I was told a some time ago when I owned a G35 that newer AC systems benefit from regular use so this may well be true. That may only refer to keeping the system charged but I have since tended to keep the AC on and just use the temperature knob to keep the cabin comfortable.
 
One other odd quirk about this:

Since some of our AC compressors seem to fail due to dried seals from lack of use over the Winter; using it as a general rule may help it to last longer.
Very good point, however, most modern HVAC systems utilize the air conditioner when the defroster is on, and some even when the heat is running. I can distinctly hear the click of the AC clutch engaging when I press the auto climate button.
 
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