|
700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
Information |
|
Air vents won't shut offViews : 601 Replies : 18Users Viewing This Thread : |
|
Thread Tools | Display Modes |
Feb 21st, 2024, 14:22 | #1 |
Master Member
Last Online: May 13th, 2024 00:33
Join Date: Jul 2021
Location: United Banana Republic of Portugal
|
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?
__________________
Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. |
Feb 21st, 2024, 15:45 | #2 |
Premier Member
Last Online: Yesterday 12:45
Join Date: Sep 2014
Location: Bristol
|
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. |
The Following User Says Thank You to tofufi For This Useful Post: |
Feb 21st, 2024, 16:41 | #3 | |
Master Member
Last Online: May 13th, 2024 00:33
Join Date: Jul 2021
Location: United Banana Republic of Portugal
|
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?
__________________
Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. |
|
Feb 23rd, 2024, 08:37 | #5 |
Master Member
Last Online: Yesterday 13:14
Join Date: Feb 2006
Location: Amersfoort (NL)
|
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? |
The Following User Says Thank You to Rversteeg For This Useful Post: |
Feb 23rd, 2024, 09:40 | #6 | |
Master Member
Last Online: May 13th, 2024 00:33
Join Date: Jul 2021
Location: United Banana Republic of Portugal
|
Quote:
If this is not the issue, I guess I might have a leak in this system!?
__________________
Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. |
|
Feb 23rd, 2024, 09:51 | #7 | |
Master Member
Last Online: May 13th, 2024 00:33
Join Date: Jul 2021
Location: United Banana Republic of Portugal
|
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!
__________________
Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. |
|
Feb 23rd, 2024, 11:50 | #8 |
Master Member
Last Online: May 13th, 2024 00:33
Join Date: Jul 2021
Location: United Banana Republic of Portugal
|
Upon further reading, my issue seems to be consistent with either one of these valces being faulty, or a faulty Floor/defrost Vacuum Bellows (9463042).
The speed knob has Auto before 0 so I suppose it is ECC right?
__________________
Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. Last edited by SalvadorP; Feb 23rd, 2024 at 13:08. |
Feb 23rd, 2024, 14:09 | #9 |
Master Member
Last Online: Yesterday 13:14
Join Date: Feb 2006
Location: Amersfoort (NL)
|
I found these pictures on the internet where you can zoom in on the check valves. Yours seem to be orientated the same way. These valves will keep the overpressure in the intake manifold (from the turbo) away from the vacuum system and only let air pass if there is a vacuum in the manifold (eg idling or when engine braking).
You have indeed the ECC system, in which case the shutters are still vacuum operated, but operated by an electric valve unit, controlling the vacuum to the vacuum servo's (did you check fuse 16?). See enclosed diagrams: as you have been fiddling with check valves item 10 and these are a common point for all valves, it would be my starting point for fault tracing. |
Feb 23rd, 2024, 14:51 | #10 |
VOC Member
Last Online: Yesterday 23:35
Join Date: Feb 2008
Location: Gloucester
|
I’ve attached a picture of these valves from my 1997 car with ECC. Mine have never been disturbed and appear to be the same orientation as yours.
Problems with the vents are often down to the vacuum servos. Your symptoms seem a little different from the normal face vents stop blowing air when the car is under acceleration There are details on replacing these units in the FAQ. https://www.volvoclub.org.uk/faq/OEM...tVacuumMtr.pdf It is possible to bypass the one that most often leaks by disabling the recirculation feature which might be worth exploring if only as a non-destructive test. |
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
|
|