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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Air vents won't shut offViews : 558 Replies : 18Users Viewing This Thread : |
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Feb 21st, 2024, 14:22 | #1 |
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Air vents won't shut off
The air vents won't shut.
I don't know if this happens with the car stationary at idle, but while driving it is really bad, especially at night when it is cold. The vents keep pumping cold air into the cabin (the heater matrix is diverted) even when the blower is off. What may be the cause of this and how can I fix it?
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Feb 21st, 2024, 15:45 | #2 |
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I'm pretty sure it is usual to get airflow through the cabin at moderate and higher speeds.
It's caused by high pressure around the base of the windscreen. I'm pretty sure the Volvo ACC (Automatic Climate Control) even reduces the fan speed accordingly at higher road speeds. |
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Feb 21st, 2024, 16:41 | #3 | |
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Quote:
This has to be some kind of gasket that is faulty or I don't know what. But it can't be by design. It's like you basically have the blower turned on one (at least) with all vents opened at the same time. I don't kow how this system is designed. What is it that make sthe air circulate one way or the other when you turn the vents knob? Is it a flap inside the ducts?
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Feb 23rd, 2024, 08:37 | #5 |
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Vacuum controlled
The air vent shutters are vacuum controlled. I am not sure if without vacuum they are spring loaded open or closed.
Do you have a manual system or ECC? |
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Feb 23rd, 2024, 09:40 | #6 | |
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Quote:
If this is not the issue, I guess I might have a leak in this system!?
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Feb 23rd, 2024, 09:51 | #7 | |
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Quote:
Can you know the proper installation direction just by the color white/black, or is there more to it? I guess if it is installed the wrong way it might causing a vacuum leak!
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