Air vents won't shut off

[SalvadorP]

Originally Posted by Rversteeg

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.

Alright, thanks for the info. Is there a way to check these one way valves?
I'll check fuse 16.

I was reading about this the whole afternoon, and I'm pretty convinced at this point that the heater vacuum bellow/servo is probably the culprit, but I'll check the easier to change parts first.
Having said that, is there currently a good way to fix/replace the servo membrane? I found people using a membrane from a GM servo, but it's not available in europe, as it is from a 80s corvette.

Another thing. I know you replaced your matrix with a Nissens, do you know the size? I find 2 different nissens models with vastly different sizes for sale under the same part number.
Does anyone know if these measurements are currect?
width (mm):177
length (in mm):240
thickness (mm):42
original Number:1307236

[SalvadorP]

Originally Posted by Forrest

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.

Thx forrest. If you can, read my last comment, replying to Rob. So I don't have to repeat it. But long story short I have come to the conclusion that it is most likely the servo, and since I do have to replace the matrix too, I might as well do both. But I'm unsure of the best way to repair/replace the servo and the currect matrix size. See the last comment please. Thanks.

edit: btw, thanks for the link. i had also just found the faq for repairing the servo but I was just beggining to read it: https://www.volvoclub.org.uk/faq/Hea...eplacement.htm

[SalvadorP]

btw, one detail that I failed to mention but now seems relevant, a few weeks/months ago, I had a trip in which the ac light started blinking and I believe it kept blinking all the way home. but the next trip it wasn't blinking anymore.

Edit: oh, now it's all coming up. The car has this weird issue (had it since I bought it) that the ac will only stay on for a bit then go out, then on. I never associated it with the acceleration, but now I'm thinking it might be related too.

[Forrest]

When the blue a/c light is flashing it indicates a fault has been detected in the ECC system. You can read off diagnostic codes by following the instructions here:

https://www.volvoclub.org.uk/faq/Hea...iagnosticCodes

These are very often obscure transient issues with sensors. I once had an error for the ECC ambient temperature sensor (separate from the optional dash temperature gauge sensor) which in those days was still available from Volvo. It took a long time for the parts department to find it in the drawings though.

The problem with your a/c cutting out after a period of use sounds very similar to a problem I fixed a couple of years ago. Mine was due to an excessive clutch gap on the Zexel compressor. With the right tools an easy fix which does not involve evacuating the system. See my thread here:

https://www.volvoforums.org.uk/showthread.php?t=326882

[SalvadorP]

Originally Posted by Forrest

When the blue a/c light is flashing it indicates a fault has been detected in the ECC system. You can read off diagnostic codes by following the instructions here:

https://www.volvoclub.org.uk/faq/Hea...iagnosticCodes

These are very often obscure transient issues with sensors. I once had an error for the ECC ambient temperature sensor (separate from the optional dash temperature gauge sensor) which in those days was still available from Volvo. It took a long time for the parts department to find it in the drawings though.

The problem with your a/c cutting out after a period of use sounds very similar to a problem I fixed a couple of years ago. Mine was due to an excessive clutch gap on the Zexel compressor. With the right tools an easy fix which does not involve evacuating the system. See my thread here:

https://www.volvoforums.org.uk/showthread.php?t=326882

Thanks forrest. I think you might be right about the AC thing. I have seen RobertDIY fixing the issue and I have known of this issue simce even before I bought my car, because it was pointed as one common failure. I think we are talking about the same failure/fix. He fixes it with zipties. https://www.youtube.com/watch?v=ReG1uQiMhm8

The reason I mentioned it here, is that thinking of it, I am not sure if the ac doesn't also switch to the feet under acceleration. I probably need to go for a drive ans test these things. But it seems very likely that the vacuum bellows is bad. Have you veer had to solve this? I'm surprised there isn't more info about this on the forums since it seems to be a common point of failure.

[Forrest]

I think the reason Robert uses the zip tie bodge is because he’s working on an 850 where access is difficult. There is no excuse for not doing the job properly on a 900 series where access to the compressor is easy. You want to set the gap at about 0.3mm using a feeler gauge.

The 960/V90 will turn off the compressor under hard acceleration by design. I don’t know whether the 940 is that sophisticated.

The vents changing dependent on the level of vacuum being pulled at the manifold does sound like a vacuum leak somewhere. I don’t think there is a magic wand for knowing where that leak is without properly testing the system and its components. I find a cheap handheld vacuum pump the easiest way to test vacuum-operated components, but you can just suck on them!

[SalvadorP]

Originally Posted by Forrest

I think the reason Robert uses the zip tie bodge is because he’s working on an 850 where access is difficult. There is no excuse for not doing the job properly on a 900 series where access to the compressor is easy. You want to set the gap at about 0.3mm using a feeler gauge.

The 960/V90 will turn off the compressor under hard acceleration by design. I don’t know whether the 940 is that sophisticated.

The vents changing dependent on the level of vacuum being pulled at the manifold does sound like a vacuum leak somewhere. I don’t think there is a magic wand for knowing where that leak is without properly testing the system and its components. I find a cheap handheld vacuum pump the easiest way to test vacuum-operated components, but you can just suck on them!

Matthew's guide for finding leaks says a leak at the level of the heater/ac bellows wouldn't give engine issues unless the direct line providing the vacuum was faulty. I imagine he was reffering to the hose that goes from the manifold to the one way valves which in my case is brand new. I have tested the system with a vacuum gauge and I couldn't find any leaks and most hoses are brand new.
Do you know if the vacuum line after the one way valve goes directly to this servo? If so, would sucking or using a handheld pump allow to diagnose if it is bad? My reasoning is that if the line is a direct connection and you vacuum it, if it doesn't hold any vacuum, it's probably either the line that is ruptured or more likely, the diaphragm. Am I thinking right?

[Forrest]

No. It’s all controlled via an electric servo on the ECC. On standard AC the vacuum lines go straight into the control module. Have a look at the attached.

[SalvadorP]

Originally Posted by Forrest

No. It’s all controlled via an electric servo on the ECC. On standard AC the vacuum lines go straight into the control module. Have a look at the attached.

Alright, so I'll have to do it another way. Either way I have to replace the matrix, so I will have to get there. My issue is that if the valve is bad and I don't have a solution right then and there, I have to reassemlble eveything, find a solution and then repeat the whole process. But I don't wanna spend 100€ on a landed GM part with the risk of not needing it.

I may go the route of the baby bottle silicone teat, or even casting the nipple myself.
Since the part isn't available anymore, it would be nice if someone found a reliable and sustainable way of fixing this thing. If I had access to a 3d printer I would just make the mold and cast a few of them. But lets see.

Thanks for the pdf, that's great. The only comprehensive illustration of this system I have seen so far. Where did you get it?