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Very high pitched frequency noise with AC/heat on

25K views 33 replies 15 participants last post by  @GolfDad5 
#1 · (Edited)
I read in another thread about a whining noise when the AC or heat is turned on:

A person posted the exact sound here:


Since this summer, I've noticed a very high pitched frequency noise whenever I have the AC or heat turned on.
It's not a terribly loud whining, but it's definitely there and somewhat annoying.
The sound goes away when I turn off the fan.

I've already changed out my cabin air filter not that long ago, so I don't think it's that.

Anyone else experiencing this type of noise?
 
#6 ·
I had my blower motor replaced after about a year of having the car, noise was not tolerable or acceptable to me. New one was whisper quiet when put in. Key word on that "was" as the replacement is starting to sound like the original did.
 
#14 ·
Chalk me up as another repeat blower motor issue-haver. Mine was replaced after about 5K miles/6 months. I'm now at 22.5K/25 months and need to have it done again. Cabin filter has been replaced twice. In both cases, it started intermittently and then became more consistent. Hoping to have the blower motor replaced when I bring the car in for the PCV/ECM recalls.

If this is going to be an ongoing issue, I'm hoping this might be a relatively easy fix in the driveway with only needing to remove the glove box to repair. Looks like the part number is 72223FL00B.

Good Luck to the OP.
 
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#9 ·
I dealt with the same issue for months, and it was driving me crazy. I decided to approach the dealership about it, and even made a video of it with my phone in case they couldn't replicate the problem. When I went to the dealership to deal with a recall, I told them that I wanted them to fix this as well. They replaced the blower motor (still under warranty) no questions asked, and now it's perfectly quiet. Hopefully your dealership will do the same for you.
 
#13 ·
Did they have the part on hand, or do you have go back another time?
I'm going to the dealership this Thursday for the recalls and this issue. I already stated in the online appt scheduler, "Blower motor needs replacement." And I video'd the car with the sound.
I'm ready for them!
 
#15 ·
I have this same problem but it only seems to be an issue when the temperature is below 45F-50F and gets progressively worse as the temps get colder. Also only at certain fan speeds but most noticibly at the lowest 2 speeds. Once the motor gets warm it goes away, and once summer hits its whisper quiet again.
 
#16 ·
How hard is it to get to the blower motor... how much of the dash needs removed to get it out?

If this is anything like the countless motors I've worked on in my life the problem can be solved with a couple of drops of (what I use) 0W30 synthetic motor oil, or whichever synthetic motor oil you have on hand.

I have a little plastic needle tipped dropper bottle I keep filled with said oil. I oil my HVAC motors with it regularly, motors in heaters, microwaves, computers, and all other motors resume quiet running after a couple drops on their shaft bushings. When popular, record turntables failed most often due to dry/sticky bearings. They're almost all sintered, or porous bronce bearings meant to be maintenance free... but used enough or long enough in certain environments, such as in higher heat as well as colder swinging applications they run out of whatever little oil was in them new.

In my home maintenance cases I keep a schedule that precludes motor bearing noise, preferring preemptive oiling over having bearing get dry or sticky and wearing their tolerances larger. Keep them oiled and quiet and their lifetime is extended long into a trouble-free future.

As they come, oilite bearings do not have synthetic lubricant in them (based on personal experience not lab results) and are best run at moderate temperatures... at best. The embedded oil both ages poorly and dries out in time, leaving the bearing job to the porous bronze or iron, with the resulting noises that result. A good synthetic oil restores the oil inside the bearing and fills the shaft/bearing clearances so the rotating parts ride on oil instead of metal.

There is no reason to suspect the blower motors are any different... but I'd have to have more information, like looking at one personally. But if you have a noisy blower motor and are up to the task, try a couple drops of oil on its bearings. It should become quiet and stay that way a long time.
 
#17 ·
How hard is it to get to the blower motor... how much of the dash needs removed to get it out?

If this is anything like the countless motors I've worked on in my life the problem can be solved with a couple of drops of (what I use) 0W30 synthetic motor oil, or whichever synthetic motor oil you have on hand.
I was hoping to dig into how much effort it was going to take to get the motor out and do this exact thing, but winter came fast and it looks like it won't be till spring when I get a chance.
 
#18 · (Edited)
I just looked at mine and it doesn't look hard at all. All I did was drop the glove box out and there the motor housing is, behind the right side of the box.

The motor is attached by three screws from below as the motor is secured to the underside of the housing,,, meaning the three or four pieces of trim and facia on that side must also be removed to do this. No big deal.

I tested mine's sounds in the garage without the engine running and it was all but indiscernable at the lowest setting with just the sound of rushing air as speed was increased, but no blower motor sounds at all. Buttoned it up, knowing now what I'll be facing if/when mine starts complaining.

From an engineering standpoint, mounting the motor horizontally facing upward is the ideal orientation for the bearings. Once again, every nook and cranny I look in in this Impreza shows a vehicle created from an entirely new perspective, where no stone was left unturned by engineers given free reign to do it right from the beginning.

 
#30 · (Edited)
From an engineering standpoint.....
no stone was left unturned by engineers given free reign to do it right from the beginning.
I can hear my blower-motor at some of the speed settings. My 'tuned' engineering ears are telling me that Subaru has changed the design from using a "blower resistor" to using PWM (Pulse Width Modulation) to control the rotational speed of the blower-motor.

PWM is a totally electronic way to control the speed of a DC motor. It is less costly than blower-resistor and allows for computer-controlled rpms.... but has some side-effects. With PWM, the motor is fed with a PULSED signal to control its speed. This means the windings of wire within the motor can react almost like a loudspeaker and resonate under some conditions. What we are hearing is the pulsing of the signal fed to the motor.

This is NOT really a "fault" nor "failure" of the motor nor its bearings...it is simply a side-effect of PWM. To keep the motor quiet, its design really needs to be modified to allow for PWM speed control. (The windings may need additional varnish to stabilize them) I am sure Subaru will figure this out and adjust the motor-design.

The reason some folks may hear the resonation at colder temperatures is because the computer detects and reacts by changing the pulse-width when motor is cold. Adding lubrication obviously changes the loading on the motor and the resultant frequency of PWM may change to non-resonant (audibly).

The radiator-fans on many vehicles have been PWM controlled for years. The SOUND of the radiator-fans is far enough away from the drivers ears such that noone can hear any resonation.
 
#19 ·
Just got back from Stohlman Subaru in VA.
They're replacing the blower motor... part needs to be ordered, so won't have it fixed until next week.
I did get the two active recalls taken care of.
I suspect everyone's 5th Gen Impreza will need the blower motor replaced eventually, unless you're an old fart and can no longer hear higher frequencies. LOL!
Thankfully, I still have 1 more month on my warranty!
 
#23 ·
They're never meant to be replaced. None of those kind of bearings are.

As I've mentioned, oil is what keeps them working. If it's worn too badly from being run too long after it began evidencing symptoms of running dry, i.e., noisy, the motor must be replaced.
 
#29 ·
Quick update on my fan. It had been getting worse so I took the fan out and sprayed some lube in the motor and inspected all the parts. It didn't really help. After the end of the summer, I took it out again and smacked the end of the metal shaft with a hammer. That seemed to do the trick. The noise hadn't come back.
 
#32 · (Edited)
I'll add to this olde post...

3ish years ago I used a long covid q tip with a drop of motorkote (hyperlube) on it. Touch the bearing at the top of the blower motor (the source of noise usually) and forget about it.

I waited for longevity sake but I'm on the orig motor that WAS shrieking and its been silent and working since.

I wouldn't spray anything INTO the motor tho, they don't last long that way if you hit the wrong thing.

02/04/24 hasn't made a peep and still working 100% 2017 on orig blower motor 130k(kms) so far
 
#34 ·
Currently dealing with this in 22 Forester. Whistling noise when car is cold. Once car warms up noise goes away. They already changed the blower motor then said it was the o-ring on the a/c compressor. None of these helped. It starts at the 76 degree setting in full auto mode. As fan speed decreses noise is present . Pretty aggravating considering I bought this car brand new.
 
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