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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 : 462 Replies : 18Users Viewing This Thread : |
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Feb 23rd, 2024, 15:27 | #11 | |
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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
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Feb 23rd, 2024, 15:32 | #12 | |
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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
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Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. Last edited by SalvadorP; Feb 23rd, 2024 at 15:34. |
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Feb 23rd, 2024, 16:26 | #13 |
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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.
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Proud owner of a 1997 940 2.3 lpt Manual with 501,000km. Last edited by SalvadorP; Feb 23rd, 2024 at 16:38. |
Feb 24th, 2024, 02:13 | #14 |
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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 |
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Feb 24th, 2024, 11:26 | #15 | |
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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.
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Feb 24th, 2024, 11:46 | #16 |
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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! |
Feb 24th, 2024, 12:16 | #17 | |
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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?
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Feb 24th, 2024, 20:12 | #18 |
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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.
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Feb 24th, 2024, 20:40 | #19 | |
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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?
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