W140 AC Defrost Vent Always Blowing Air
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Junior Member
Joined: Jan 2026
Posts: 1
W140 AC Defrost Vent Always Blowing Air
Hello Everyone,
I recently got a 1999 Mercedes-Benz S 420. I noticed that the windshield defrost vent always stays on. I cannot get it to turn off. From right when I start the car it is on and when I turn the car off and take the key out it takes a few seconds for it to turn off. I noticed the middle vents do not blow air but the side vents do blow cold Air. The heater is also not working it only blows cold Air.
Any ideas how to fix the defrost vent to be able to turn it off.
Thank you!
I recently got a 1999 Mercedes-Benz S 420. I noticed that the windshield defrost vent always stays on. I cannot get it to turn off. From right when I start the car it is on and when I turn the car off and take the key out it takes a few seconds for it to turn off. I noticed the middle vents do not blow air but the side vents do blow cold Air. The heater is also not working it only blows cold Air.
Any ideas how to fix the defrost vent to be able to turn it off.
Thank you!
Junior Member
Joined: Jun 2021
Posts: 20
Hie man I'm from Zimbabwe my father has GLS 400D 4matic so rear and front left AC is functioning good front right is always blowing hot air where which position can I found that thing u changed on your Benz on my father's.
192.168.100.1 192.168.1.1
192.168.100.1 192.168.1.1
Last edited by dhaauxx; Feb 16, 2026 at 09:23 AM.
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