XC90 ringing noise, on/off with A/C

[Goldensyrup]

Hello,
can anyone shed any light on what might be the problem I'm experiencing, please?

There's a sort of ringing or singing noise in the cabin, that is associated with the air conditioning. It goes away promptly when one turns the a/c off, and returns promptly when a/c is turned on again.

It's a noise at about 750Hz. (Just over one octave higher than middle C!) So not very high. It's not like a cricket noise.

It is unaffected by the speed of the blower fan.

Changing engine RPM seems to affect it a little - makes it a bit louder, but doesn't change pitch.

Here's a video of the actions that turns the noise on and off: it's possible to hear the noise quite clearly on the video if you're listening on headphones or a good sound system!
https://youtu.be/EiyBUNnfp_k

Could it be the air conditioning expansion valve? Something else? I could imagine it being a bearing problem or something.

Any ideas? Thank you!

[Moose Test]

Originally Posted by Goldensyrup

Could it be the air conditioning expansion valve?

Any ideas?

I've experienced the same (or very, very similar): https://www.volvoforums.org.uk/showt...itioning+whine

I had the expansion valve replaced and the noise went. For about 6 months. So to be honest, I'm not sure what is really happening but my ultimate "solution" has been to learn to live with it.

Perhaps the Friday afternoon / Monday morning cars get extra bends, dents or kinks in the pipework when fitted?

[Goldensyrup]

Thank you - I had seen your thread and wondered if it was the same issue.

Having replaced the expansion valve, does it need regassing, or it is that straightforward? I' watched a YouTube video, but may yet outsource it to a local specialist.

I've been living with it for ages! It's annoying though - the 3.2 litre engine is so smooth and quiet that this noise really detracts from the enjoyment! First world problem, granted.

[Moose Test]

That's interesting, that you should also be running a petrol model. As you say, they are that much quieter inside than the oil burners the intrusion of this noise is particularly annoying. I wonder now whether that's part of the story. I doubt that there is a design or manufacturing issue specific to petrol vehicles but perhaps the lack of engine noise makes it more likely to be noticed on affected units.

I had the supplying Volvo dealership replace the expansion value, so I can't say for sure what that process involves. However I strongly suspect that it includes a full drain under vacuum and recharge of the refrigerant circuit. Simply venting refrigerant to atmosphere is a legal no-no for garages but even if you were to do the work yourself, I don't believe there to be any isolation valves which would prevent the entire system degassing if you were to open it at the expansion valve.

[Goldensyrup]

I'm now waiting on a call back from the local main dealer. I would be mighty surprised if they get the gig, however.

Yup, the petrol models are very nice. A friend told me that some years back he had the pick of them all, and selected the 3.2 petrol as the nicest of the lot. I've grown to like it. Actually has an LPG conversion, so even with dwindling availability of LPG, it ends up being (just) tolerable to run it!

[Moose Test]

Good luck with it, I hope it resolves the issue for you. Mine was instantly improved but as said previously, that improvement didn't last for very long and the noise I experience has already been at its original level for some time now.

I can't believe that the new valve wore out so quickly, I'm more inclined to think that in my case at least, it was the action of perturbing the fluid system through draining and refilling that caused the temporary relief. Similar to having an airlock in hydronic central heating. Air bleed and refill can temporarily remove or move the lock but ultimately there's a persistent root cause for the lock and it will return.

I agree with you on main dealer labour rates. This is a job that is relatively simple on the XC90, with the valve being accessed from the engine side of the bulkhead, rather than having to strip out the dash and dig down into sections of the air handling. An aircon specialist might be a better option. However the cost of draining, vacuuming and refilling can't be avoided.

[Goldensyrup]

Updating here.
Had ac drained, replaced expansion valve, plus more seals, regassed. Noise is… a little bit better, maybe? It has, sadly, not been the magic bullet.
Still rings, is still annoying. But if it’s a bottomless hole to pour money into, I’ll live with it. And changing the torque converter is a higher priority. Boo.

[Moose Test]

Thanks for updating, again, interesting. I'm sorry to hear that it wasn't a resolution for you either.

Mine did at least go quiet for a handful of months before returning to previous levels. I've no idea what the root cause is on the basis of these experiences so, like you, my plan has become to live with it too.