2008 V70 - HVAC whine during colder months

its4uok · Post by **its4uok** » 23 Jan 2018, 09:13

I'm looking for some help diagnosing a noise on my 2008 V70. There is a noticeable whine coming from the dash area which changes pitch with the RPMs of the engine. The noise completely disappears if I shut the HVAC off which has always led me to believe the blower motor is the culprit. The odd aspect of this is that the noise is really only obvious when temperatures are below 45 degrees F.

Considering the complexity of swapping out the blower motor I'd like to be certain that is the issue prior to tackling that.

Post by **RickHaleParker** » 23 Jan 2018, 09:48

I would reach in and unplug the blower motor when the whine is present, see if that stops the whining.
If it does stop whining, next I would turn off the HVAC and power the blower motor directly with jumper wires for confirmation.

its4uok · Post by **its4uok** » 24 Jan 2018, 07:22

Played with this a little more last night and did find that the whine goes away when you turn the A/C off. Fan was still blowing and it was quiet.

Post by **oragex** » 24 Jan 2018, 08:45

The cabin fan blower does go bad and is located right behind the glove box, it makes a high pitching noise, like a complain. It starts in cold weather and changing the fan speed at the knob may change or even take away this noise.

However the cabin fan is not affected by the engine revs, so perhaps you have a different issue.

The bearing on the air climate compressor (located just under the alternator) starts getting dry at 100K miles or so and it's making a friction noise. This bearing can be replaced relatively easily without removing the compressor. Finally, just above the alternator is the power steering pump. All these three are driven by the same belt. The power steering pump is the one more likely to make a 'whine' noise in particular if the fluid is low or if the fluid is the wrong type - it should be a clear green almost fluo color. The pump rarely goes bad, only the fluid needs replaced with the correct one, the Pentosin chf 201 or 11.

I would ask a mechanic to remove or toss the accessory (serpentine) belt, and to spin all these pulleys by hand, then check the fluid in the power steering pump reservoir.

Post by **RickHaleParker** » 24 Jan 2018, 09:55

Now I'm baffled as to why this is an issue. Who needs A/C at 45°F?

its4uok · Post by **its4uok** » 29 Jan 2018, 08:04

I'm going to have my independent mechanic look at it as soon as he located a part for a different issue (Brake Booster). Some of the other posts I've looked at suggest low Freon can create this noise. I'll do my best to update the outcome once we get it resolved.

As for A/C in the winter, you can run A/C and Heat to dry out the air in the cabin and prevent moisture on the windows. In this case though we are just setting the Climate Control to Auto and letting it make the decisions for us.

Post by **abscate** » 09 Feb 2018, 10:29

The cabin fan blower does go bad and is located right behind the glove box, it makes a high pitching noise, like a complain. It starts in cold weather and changing the fan speed at the knob may change or even take away this noise.

HVAC fan on a P3 is a major Charlie Foxtrot. Diagnose first.

its4uok · Post by **its4uok** » 06 Apr 2018, 12:10

Just to closing the loop on this one.

Long (and not useful) story but we ended up going ahead and replacing the compressor and i have not heard the whirring noise since.

Post by **abscate** » 07 Apr 2018, 05:04

Thanks for closure. AC is triggered whenever one selects defrost, but only above 35F.

I think I may have found the reason for this, I left some PAG oil outside and it turned into Jello in the low 30s