[constipated]

The air conditioning in my car is starting to make a whining noise. Goes away immediately the air con button is switched off even if the fan continues. Most audible inside. Under the hood I thought the noise was coming from near the radiator but that sound seems to continue even with a/c off.  It probably gets lost mixed in with the diesel engine rattle.

The car is being attended to for other issues by the dealer later this week. What could be the problem and where should I direct them to look?

[Dazzler]

I had a similar issue with both my hybrids, but they reckoned the air con was working up to spec on both. 

[Phil №❶]

If you can't identify a mechanical cause, could it possibly be the expansion valve in the evaporator, just a guess.

[elantraelite]

All the Hyundai's I have had have made this sound here and there. My X3 Excel was the noisiest, However after 300,000km and being 15 years old, the AC was ice cold.
I would be concerned about it

[constipated]

All the Hyundai's I have had have made this sound here and there. My X3 Excel was the noisiest, However after 300,000km and being 15 years old, the AC was ice cold.
I would be concerned about it

They couldn't find anything but have noted it down. Air con is still very cold so I'll just grin and bear it.

[Just Rick]

All the Hyundai's I have had have made this sound here and there. My X3 Excel was the noisiest, However after 300,000km and being 15 years old, the AC was ice cold.
I would be concerned about it

They couldn't find anything but have noted it down. Air con is still very cold so I'll just grin and bear it.

Did ou ask them whether they removed the serpentine belt and check the condition of the idler pulleys,I had one very close to collapsing it was making similar type noises to this,many Tech these days can't be bother looking past their noses to find issues,took Hyundai 30 months to fix a alarm and light locking issue in Cyril when we had him,the last service I ever got Hyundai to do they had employed a new(older Mechanic)I explained the issue to him and he went straight to the problem,without a computer or any other electronic gizmo's,good ol fault finding techniques