Humming noise from dash when the A/C is on

X5only · #1 11-16-2011, 02:35 AM

A soft, persistent humming when the A/C is on. Turn off the A/C (toggle the A/C button off), no hum. Turn the A/C back on: humming noise....Seems to be coming from somewhere behind the dash.

I don't think it would be the blower motor since leaving blower on with A/C off does not make the noise. Anyone here fixed this A/C issue? Could it be the compressor? I'd replaced the belts and pulleys but noise still there.

2005 X5 4.4 sports

X5only · #2 11-17-2011, 09:38 PM

ANy a/c expert out there?

X5only · #3 07-27-2021, 03:39 PM

I'm told that the continuous humming noise coming from the dash during A/C operation is the A/C expansion valve. The blower motor has been proven not to make the humming noise. The noise only happens when the A/C is turned on. Is the expansion valve known to make a humming noise? I'm kinda skeptical about this diagnosis.

So far I've vacuumed the blower motor itself and lubed it a little. Yes, there were leaves, bugs and a piece of black cloth tape in the various chambers in there. I vacuumed out all dirt and installed a new microfilter. Noise still persists to-date.

https://www.youtube.com/watch?v=XLKx7-m5LUQ&t=8s

Any ideas?

X5chemist · #4 07-27-2021, 04:36 PM

I've worked on a few vehicles with expansion valves. I've never heard one hum. Do you have a mechanic stethoscope? Pull down the glove box and try to find a better hum location.

X5only · #5 07-27-2021, 05:36 PM

Quote:

Originally Posted by X5chemist

I've worked on a few vehicles with expansion valves. I've never heard one hum. Do you have a mechanic stethoscope? Pull down the glove box and try to find a better hum location.

Sounds like a good pointer there. Thanks! From your experience, would low refrigerant level likely to cause a humming noise from the A/C system?