Odd noise from air con, Mondeo (2008)

spratley

2008 2.0L petrol Mondeo - when the aircon fan is running, it is slightly noisy. Sounds like a background resonance/vibration that comes and goes. Most noticeable on the lowest fan setting - not terribly noisy, but annoying! Also, the fan speed seems to vary a bit - it slows down as if struggling slightly, then goes back to normal. Without the aircon on, the fan is quiet and seems to run normally.
Any ideas, please?
Thanks!

Rapished

do you have 2 fans the red one and the aircon one?

forgotmyname

Standard aircon or climate control? The sensor that detects the cabin temperature can vibrate.

spratley

It's the base model, so it's just basic aircon. There's just one fan control "knob"...

Strider590

I doubt it's the fan, more likely coming from under the bonnet.

My Vectra has a slight whining noise with the AC running, it's the AC pump/clutch.

If it's definitely the cabin air fan, then it's likely the additional load caused by the AC, so if it almost disappears at high engine RPM, then chances are you'll be needing a new battery as soon as we get into the frosty months.

The other factor is the condition of the cabin air fan, which might have some corrosion, which is enough to cause issues when combined with the above. It's worth pulling out the pollen filter, finding the fan with a torch, squirting it with some lubricating oil (NOT WD40) and leaving it to soak for half an hour.

datostar

If the noise is coming from anywhere around the compressor/clutch get it checked fairly soon. I ignored a whine from my old Megane 2.0 compressor and the whole thing seized. The auxiliary belt held and it stopped the engine dead. Expensive repair involving a new compressor. Apparently on some cars if you catch it soon enough the compressor clutch can be fixed before the bearings collapse.